CGAL/cgal

📋 General Changes

• The new list of supported compilers is:
• Visual C++ 15.9, 16.10, 17.14, 18.0 (from Visual Studio 2017, 2019, 2022, and 2026) or later
• Gnu g++ 13.3.0 or later (on Linux)
• LLVM Clang version 22.0.0 or later (on Linux)
• Apple Clang compiler versions 14.0.0 or later (on macOS)
• The minimal supported version of Boost is still 1.74.0, but only versions 1.79.0 and later were tested.

✨ [2D Alpha Wrapping](https://doc.cgal.org/6.2/Manual/packages.html#PkgAlphaWrap2) (new package)

• This component takes a polygon soup, a 2D segment soup, and/or a 2D point set as input, and generates a valid (watertight, intersection-free and 1-manifold) multi-polygon that strictly encloses the input. The algorithm proceeds by shrink-wrapping and refining a 2D Delaunay triangulation starting from a loose bounding box of the input. Two user-defined parameters, alpha and offset, offer control over the maximum size of cavities where the shrink-wrapping process can enter, and the tightness of the final polygon(s) to the input, respectively. Once combined, these parameters provide a means to trade fidelity to the input for complexity of the output.
• See also the associated [news entry](https://www.cgal.org/2026/03/30/alpha_wrap_2/).

✨ [Generalized Barycentric Coordinates 3](https://doc.cgal.org/6.2/Manual/packages.html#PkgBarycentricCoordinates3) (new package)

• This package provides functions to compute various types of generalized barycentric coordinates (Wachspress, mean value, discrete harmonic and tetrahedron coordinates) for points located inside closed convex 3D polyhedra.

📝 [Polygon Mesh Processing](https://doc.cgal.org/6.2/Manual/packages.html#PkgPolygonMeshProcessing) (major changes)

• The “Polygon Mesh Processing” package has been reorganized into several packages. “Polygon Mesh Processing” retains the core functionalities, while advanced and specialized features have been moved to dedicated packages:
• [Boolean Operations On Meshes](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPBooleanOperations): algorithms for Boolean operations on polygon meshes; clipping, splitting, and slicing with planes, boxes, or other meshes; and kernel computations.
• [Meshing and Remeshing of Polygon Meshes](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPRemeshing): algorithms for meshing and remeshing, such as triangulation, refinement, simplification, optimization, and smoothing.
• [Polygon Mesh Repair](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPMeshRepair): tools for detecting and correcting combinatorial and geometric defects in polygon meshes and polygon soups, including face orientation, hole filling, removal of degeneracies, and boundary stitching. This split does not induce any breaking change and is fully transparent: header includes such as `#include <CGAL/Polygon_mesh_processing/XXX.h>` do not need to be changed and will include the appropriate header from the new packages.

📝 [2D and 3D Linear Geometry Kernel](https://doc.cgal.org/6.2/Manual/packages.html#PkgKernel23)

• Breaking change: The functors [`Do_intersect_2`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#a66956c9eb7a1e2042326b051ecef8020) and [`Do_intersect_3`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#adf4b45486ddac1219aa419fc62c38e1b) for intersection now correctly honor the definition of a `Circle_2` (resp. `Sphere_3`) as a 1-manifold (resp. 2-manifold) without borders. In other words, a circle is not a disk, and a sphere is not a ball. Consequently, `Circle_2`/`Segment_2`, `Sphere_3`/`Bbox_3`, `Sphere_3`/`Iso_cuboid_3` no longer consider inclusion as an intersection. This behavior is consistent with other intersection combinations involving `Circle_2` and `Sphere_3`. The former behavior can be reproduced with:
• [`!Has_on_unbounded_side_2::operator(Circle_2, Segment_2)`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#ab041aafd45ce93630bfe77cec24e24f3),
• [`!Has_on_unbounded_side_2::operator(Circle_2, Iso_rectangle_2)`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#ab041aafd45ce93630bfe77cec24e24f3), or
• [`!Has_on_unbounded_side_3::operator(Sphere_3, Iso_cuboid_3)`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#ada27f27602757133ea7b9814ada00ba3)
• Added a new concept, [`CompareProjectionAlongDirection_3`](https://doc.cgal.org/6.2/Kernel_23/classKernel_1_1CompareProjectionAlongDirection__3.html), to the [`Kernel`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html) concept to compare the order of point projections onto a line. Corresponding functors in the model, [`Compare_projection_along_direction_3`](https://doc.cgal.org/6.2/Kernel_23/classKernel.html#a4b7686814790650efe8f8b6612af3b80), and free function, [`compare_projection_along_direction()`](https://doc.cgal.org/6.2/Kernel_23/group__kernel__global__function.html#ga2ba880adb55cea48d3568ccd1f4765a4), have been added.

📝 [Intersecting Sequences of dD Iso-oriented Boxes](https://doc.cgal.org/6.2/Manual/packages.html#PkgBoxIntersectionD)

• The function [`CGAL::box_intersection_d()`](https://doc.cgal.org/6.2/Box_intersection_d/group__PkgBoxIntersectionD__box__intersection__d.html) now supports ranges with different box types.
• Added the box type [`CGAL::Box_with_info_d<FT, dim, Info>`](https://doc.cgal.org/6.2/Box_intersection_d/classCGAL_1_1Box__intersection__d_1_1Box__with__info__d.html), which stores a variable of type `Info` accessible via the class member function [`info()`](https://doc.cgal.org/6.2/Box_intersection_d/classCGAL_1_1Box__intersection__d_1_1Box__with__info__d.html#a5858777d3531cfc13bdc0fea067a7532).

📝 [2D Arrangements](https://doc.cgal.org/6.2/Manual/packages.html#PkgArrangementOnSurface2)

• Introduced a Geometry Traits concept for arrangement on surfaces that enables the provision of the disconnected portions of an approximation of a curve within a given bounding box.
• The class [`CGAL::Arr_linear_traits_2`](https://doc.cgal.org/6.2/Arrangement_on_surface_2/classCGAL_1_1Arr__linear__traits__2.html) is now a model of the new concept.
• Added overloads of [`CGAL::draw(Arrangement_on_surface_2& arr, Bbox& bbox, ...)`](https://doc.cgal.org/6.2/Arrangement_on_surface_2/group__PkgArrangementOnSurface2Draw.html) that enable the drawing of arrangements induced by unbounded curves.
• Introduced the concept `AosTraits::Do_intersect_2`. A model of this concept must provide an operator that accepts two `x`-monotone curves and a boolean flag that indicates whether common endpoints should be considered or ignored. The operator determines whether the curves intersect, and it can be used with an inexact-construction kernel.

📝 [2D Intersection of Curves](https://doc.cgal.org/6.2/Manual/packages.html#PkgSurfaceSweep2)

• The function [`CGAL::do_curves_intersect()`](https://doc.cgal.org/6.2/Surface_sweep_2/group__PkgSurfaceSweep2Ref.html#gadb96b95f091371e834e3f7b4d24f7bb4), which assumed open curves, has been deprecated and replaced by the function [`CGAL::Surface_sweep_2::do_intersect()`](https://doc.cgal.org/6.2/Surface_sweep_2/group__PkgSurfaceSweep2Ref.html#ga6de86b9ce9ed5537d371142716cf8adf). Notice: (i) the introduction of the new namespace `Surface_sweep_2`, and (ii) the addition of the `closed` parameter, which defaults to `true`. To match the behavior of the deprecated function, set `closed` to false.

📝 [2D Regularized Boolean Set-Operations](https://doc.cgal.org/6.2/Manual/packages.html#PkgBooleanSetOperations2)

• Optimized [`do_intersect()`](https://doc.cgal.org/6.2/Boolean_set_operations_2/group__boolean__do__intersect.html):
• (i) made it robust even with an inexact-predicates kernel, and
• (ii) made it quit once an intersection is detected. (In the past, the intersection was computed in one phase and examined in a subsequent phase.) This optimization somehow breaks backward compatibility as follows: the variants of the free function `do_intersect()` that accept a third optional parameter, namely `UsePolylines`, which determines whether the boundaries of the input polygons are treated as cyclic sequences of (`x`-monotone) segments or as a cyclic sequences of (`x`-monotone) polylines, do not accept this third parameter any longer. (This third optional parameter was introduced a few years ago, and now abandoned only for `do_intersect()`.)

📝 [3D Convex hull](https://doc.cgal.org/6.2/Manual/packages.html#PkgConvexHull3)

• Added the function [`CGAL::Convex_hull_3::do_intersect()`](https://doc.cgal.org/6.2/Convex_hull_3/group__PkgConvexHull3Intersections.html#gaf41281925d9bf8b5b0c6e13851d900c7), which can be used to test for intersection between two convex hulls.
• Added the function [`CGAL::extreme_point_3()`](https://doc.cgal.org/6.2/Convex_hull_3/group__PkgConvexHull3Queries.html#ga329e2cdfdc3bdf89a47073c277ce202d), which returns the farthest point of a convex hull in a given direction.
• Added the class [`CGAL::Convex_hull_hierarchy_3`](https://doc.cgal.org/6.2/Convex_hull_3/structCGAL_1_1Convex__hull__hierarchy__3.html), which represents a convex hull, and is optimized for the functions above.

📝 [2D Triangulations](https://doc.cgal.org/6.2/Manual/packages.html#PkgTriangulation2)

• Added the function [`insert_unique_constraints()`](https://doc.cgal.org/6.2/Triangulation_2/classCGAL_1_1Constrained__Delaunay__triangulation__2.html#a228faa9b87674183d88e3858851e9747) to the class [`CGAL::Constrained_Delaunay_triangulation_2`](https://doc.cgal.org/6.2/Triangulation_2/classCGAL_1_1Constrained__Delaunay__triangulation__2.html) identical to the function [`insert_constraints()`](https://doc.cgal.org/6.2/Triangulation_2/classCGAL_1_1Constrained__Delaunay__triangulation__2.html#a2fa90339d0c18d07c60857fe42acab2a) except that it removes duplicated constraints before inserting them in the triangulation.

📝 [2D Conforming Triangulations and Meshes](https://doc.cgal.org/6.2/Manual/packages.html#PkgMesh2)

• The implementation is now more robust to almost degenerate inputs, such as polygons with microscopic edges or almost collinear points.
• Breaking change: The concept [`DelaunayMeshTraits_2`](https://doc.cgal.org/6.2/Mesh_2/classDelaunayMeshTraits__2.html) now requires the functor `Construct_bbox_2`.

📝 [Tetrahedral Mesh Generation](https://doc.cgal.org/6.2/Manual/packages.html#PkgMesh3)

• Breaking change: Removed the class template `CGAL::Implicit_vector_to_labeling_function_wrapper`, as well as the constructor of [`CGAL::Polyhedral_mesh_domain_with_features_3`](https://doc.cgal.org/6.2/Mesh_3/classCGAL_1_1Polyhedral__mesh__domain__with__features__3.html) that takes a filename as parameter, which were deprecated since CGAL-4.5.
• Breaking change: Added the requirement for a nested type `Iso_cuboid_3` to the concept [`BisectionGeometricTraits_3`](https://doc.cgal.org/6.2/Mesh_3/classBisectionGeometricTraits__3.html).
• Protection of sharp edges (also known as “feature line”) is now significantly faster.

📝 [dD Triangulations](https://doc.cgal.org/6.2/Manual/packages.html#PkgTriangulations)

• Computation of convex hulls in high dimensions is now significantly faster.

📝 [Convex Decomposition of Polyhedra](https://doc.cgal.org/6.2/Manual/packages.html#PkgConvexDecomposition3)

• Added the function [`CGAL::approximate_convex_decomposition()`](https://doc.cgal.org/6.2/Convex_decomposition_3/group__PkgConvexDecomposition3Ref.html#ga98ed6393d56fc2eac2ad82a55af84b2f), which computes a set of convex volumes that cover an input mesh.

📝 [Polygon Mesh Processing](https://doc.cgal.org/6.2/Manual/packages.html#PkgPolygonMeshProcessing)

• Breaking change: The header `CGAL/Polygon_mesh_processing/border.h` has been deprecated and its content ([`CGAL::border_halfedges()`](https://doc.cgal.org/6.2/BGL/group__PkgBGLHelperFct.html#gad9e4e6644bc6e2c79101b25e280ea633) and [`CGAL::extract_boundary_cycles()`](https://doc.cgal.org/6.2/BGL/group__PkgBGLHelperFct.html#ga28bba3efbd0352497f28c3c8185be09f)) have been moved to a new header: `CGAL/boost/graph/border.h`.
• Vertex normal computation is now significantly faster for high-degree vertices.

📝 [Polygon Mesh Processing (Boolean Operations on Meshes)](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPBooleanOperations)

• Added the function [`CGAL::Polygon_mesh_processing::kernel()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__kernel__grp.html#ga778059f8efd21fb9a9ffc7ede16c5abc), which can be used to compute the kernel of a polygon mesh, and is significantly faster than halfspace intersections.
• Added the function [`CGAL::Polygon_mesh_processing::has_empty_kernel()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__kernel__grp.html#gaf5b25f2dc1e3d96e9f81ed182f9600de), which can be used to determine if the kernel of a polygon mesh is empty.
• Added the function [`CGAL::Polygon_mesh_processing::kernel_point()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__kernel__grp.html#gaea657a1fbac5d35c3d51735c3ec2fede), which can be used to compute a single point inside the kernel of a polygon mesh.
• Added an optional parameter `use_convex_specialization` to the functions [`CGAL::Polygon_mesh_processing::clip()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__clip__grp.html#ga2c73d3460872e601f84a03f58dd069ae) and [`CGAL::Polygon_mesh_processing::refine_with_plane()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__slicing__grp.html#gacb9d68fa4dea8fd03ec53b56a16d6fc6), which can be used to specify that a given input is convex, resulting in much faster computation.
• The function [`CGAL::Polygon_mesh_processing::surface_intersection()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__corefinement__grp.html#ga6e6c4a724ce19e7a207de56f3a7408ab), which can be used to compute the polylines that represent the intersection between two polyhedral surfaces has been renamed to [`CGAL::Polygon_mesh_processing::intersection_polylines()`](https://doc.cgal.org/6.2/PMP_Boolean_operations/group__PMP__corefinement__grp.html#ga7da80d8488d7a9139dcabceeb601072f).

📝 [Polygon Mesh Processing (Meshing and Remeshing of Polygon Meshes)](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPRemeshing)

• Breaking change: Update the visitor concepts [`PMPTriangulateFaceVisitor`](https://doc.cgal.org/6.2/Polygon_mesh_processing/classPMPTriangulateFaceVisitor.html) and [`PMPHolefillingVisitor`](https://doc.cgal.org/6.2/Polygon_mesh_processing/classPMPHolefillingVisitor.html) to request functions [`accept_face()`](https://doc.cgal.org/6.2/Polygon_mesh_processing/classPMPTriangulateFaceVisitor.html#a62ee542bc34faafb193147c746e07a69) and [`accept_triangle()`](https://doc.cgal.org/6.2/Polygon_mesh_processing/classPMPHolefillingVisitor.html#a273b240262220abe572e42d8daef0d7a), respectively. These functions can be used to tweak the way faces and holes are triangles by black listing some candidate triangles. User visitors inheriting from the default visitors do not require any update.

📝 [Polygon Mesh Processing (Mesh Repair)](https://doc.cgal.org/6.2/Manual/packages.html#PkgPMPMeshRepair)

• Added the named parameter `erase_policy` to [`CGAL::Polygon_mesh_processing::repair_polygon_soup()`](https://doc.cgal.org/6.2/PMP_Mesh_repair/group__PMP__combinatorial__repair__grp.html#ga3b35133783759402828325b91ab559cc) and [`CGAL::Polygon_mesh_processing::merge_duplicate_polygons_in_polygon_soup()`](https://doc.cgal.org/6.2/PMP_Mesh_repair/group__PMP__combinatorial__repair__grp.html#ga1f215926ed8794db827e2993d2960870). This parameter offers three policies: (i) erase all duplicates polygons,
• 2) keep one of the duplicates (default), and (iii) keep one iff the number of duplicates is odd. The named parameter `erase_all_duplicates` is now deprecated.

📝 [Quadtrees, Octrees, and Orthtrees](https://doc.cgal.org/6.2/Manual/packages.html#PkgOrthtree)

• Added the member function [`intersected_nodes()`](https://doc.cgal.org/6.2/Orthtree/classCGAL_1_1Orthtree.html#a595f6d7c735f4c60c2c65e5ed2ef293c) [with an intersection functor](https://doc.cgal.org/6.2/Orthtree/classCGAL_1_1Orthtree.html#a18a2ac4bb94e3dbc17e556e833d2fe68) and [a convenience overload for a ball query](https://doc.cgal.org/6.2/Orthtree/classCGAL_1_1Orthtree.html#af685c4789f52eac1946add391b849777) to the class [`CGAL::Orthree`](https://doc.cgal.org/6.2/Orthtree/classCGAL_1_1Orthtree.html).

📝 [Linear Cell Complex](https://doc.cgal.org/6.2/Manual/packages.html#PkgLinearCellComplex)

• The following import functions have been deprecated and renamed for better naming clarity and consistency:
• [`import_from_plane_graph()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexConstructions.html#ga2e694849af5a899bb8545ff7ea8ab2a8) → [`read_plane_graph_in_lcc()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexConstructions.html#ga909e9e304b69e21ae3cddc0f5bb7b94a)
• `import_from_polyhedron_3()` → [`polyhedron_3_to_lcc()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexConstructions.html#gac790497ffcb75b93dc6994d8239628a9)
• `import_from_triangulation_3()` → [`triangulation_3_to_lcc()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexConstructions.html#gae0d938bab5a5da62716b67a69f4cd520) The old function names are still available but marked as deprecated for backward compatibility.
• Two functions have been added to read and write [3D linear cell complexes](https://doc.cgal.org/6.2/Linear_cell_complex/classLinearCellComplex.html) (dimension 3, ambient dimension 3) using VTK file formats (legacy ASCII):
• [`CGAL::IO::read_VTK<LCC>()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexRefIOVTK.html#ga5c283bb942b300eb47c956ae63157507), and
• [`CGAL::IO::write_VTK<LCC>()`](https://doc.cgal.org/6.2/Linear_cell_complex/group__PkgLinearCellComplexRefIOVTK.html#ga857ed2854ab8fe2c65126fb066dd5e07) These functions support per-vertex and per-volume scalar fields and handle various VTK cell types.

📝 [Shape Detection](https://doc.cgal.org/6.2/Manual/packages.html#PkgShapeDetection)

• Added the region type [`CGAL::Shape_detection::Polygon_mesh::Plane_face_region`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Plane__face__region.html) that extends the support plane of the seed face without refitting the plane to the region
• Added the region type [`CGAL::Shape_detection::Polygon_mesh::Line_segment_region`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Segment__set_1_1Line__segment__region.html) that extends the support line of the seed segment without refitting the line to the region
• Added the sorting [`CGAL::Shape_detection::Polygon_mesh::Face_area_sorting`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Face__area__sorting.html) that provides a sorting of faces in descending order of area
• Added the sorting [`CGAL::Shape_detection::Polygon_mesh::Segment_length_sorting`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Segment__set_1_1Segment__length__sorting.html) that provides a sorting of segments in descending order of length
• Added the optional named parameter `face_normal_map` to [`CGAL::Shape_detection::Polygon_mesh::Least_squares_plane_fit_region`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Least__squares__plane__fit__region.html), [`CGAL::Shape_detection::Polygon_mesh::Plane_face_region`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Plane__face__region.html); and [`CGAL::Polygon_mesh_processing::region_growing_of_planes_on_faces()`](https://doc.cgal.org/6.2/Polygon_mesh_processing/group__PMP__detect__features__grp.html#ga50dcd2f6295f584d2e378b57290ae2af) to allow the use of face normal property maps instead of calculating the face normals.
• The [`CGAL::Shape_detection::Polygon_mesh::Plane_face_region`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Plane__face__region.html) and [`CGAL::Shape_detection::Polygon_mesh::Face_area_sorting`](https://doc.cgal.org/6.2/Shape_detection/classCGAL_1_1Shape__detection_1_1Polygon__mesh_1_1Face__area__sorting.html) are now used as the default in [`CGAL::Polygon_mesh_processing::region_growing_of_planes_on_faces()`](https://doc.cgal.org/6.2/Polygon_mesh_processing/group__PMP__detect__features__grp.html#ga50dcd2f6295f584d2e378b57290ae2af)

📝 [Surface Mesh Simplification](https://doc.cgal.org/6.2/Manual/packages.html#PkgSurfaceMeshSimplification)

• Added the class [`CGAL::Surface_mesh_simplification::GarlandHeckbert_plane_and_line_policies`](https://doc.cgal.org/6.2/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__plane__and__line__policies.html), which improves other Garland-Heckbert strategies near sharp features.
• Breaking change: [`CGAL::Surface_mesh_simplification::GarlandHeckbert_policies.h`](https://doc.cgal.org/6.2/Surface_mesh_simplification/group__PkgSurfaceMeshSimplificationRef.html#ga3f012cf5dc52d6e5ac2aea1106e4cad7) is is no longer deprecated and has become an alias for the current best Garland-Heckbert policy, which is currently `CGAL::Surface_mesh_simplification::GarlandHeckbert_plane_and_line_policies`.

📝 [Geometric Object Generators](https://doc.cgal.org/6.2/Generator/index.html)

• Added three new point generators:
• [`CGAL::Random_points_on_segment_3`](https://doc.cgal.org/6.2/Generator/classCGAL_1_1Random__points__on__segment__3.html),
• [`CGAL::Random_points_in_triangle_soup_3`](https://doc.cgal.org/6.2/Generator/structCGAL_1_1Random__points__in__triangle__soup__3.html), and
• [`CGAL::Random_points_on_graph_edges_3`](https://doc.cgal.org/6.2/Generator/structCGAL_1_1Random__points__on__graph__edges__3.html)
• Added the function `point_and_support()` to several generators to get the last point generated point and the support element containing it. Affected generators are:
• [`CGAL::Random_points_in_triangles_2`](https://doc.cgal.org/6.2/Generator/structCGAL_1_1Random__points__in__triangles__2.html),
• [`CGAL::Random_points_in_triangles_3`](https://doc.cgal.org/6.2/Generator/structCGAL_1_1Random__points__in__triangles__3.html),
• [`CGAL::Random_points_in_triangle_mesh_3`](https://doc.cgal.org/6.2/Generator/structCGAL_1_1Random__points__in__triangle__mesh__3.html),
• + 4 more

📝 [STL Extension](https://doc.cgal.org/6.2/Manual/packages.html#PkgSTLExtension)

• Added new debugging utility for finding minimal failing test cases:
• [`CGAL::bisect_failures`](https://doc.cgal.org/6.2/STL_Extension/group__PkgSTLExtensionUtilities.html#gad56d708faac9063d3de057394a6d8c52) is a template function that uses bisection to isolate minimal failing subsets from complex input data.

📝 [Stream Support](https://doc.cgal.org/6.2/Manual/packages.html#PkgStreamSupport)

• Added new stream formatting capabilities for improved debugging and logging:
• [`CGAL::IO::Basic_indenting_streambuf`](https://doc.cgal.org/6.2/Stream_support/classCGAL_1_1IO_1_1Basic__indenting__streambuf.html) and [`CGAL::IO::Basic_indenting_stream_guard`](https://doc.cgal.org/6.2/Stream_support/classCGAL_1_1IO_1_1Basic__indenting__stream__guard.html) for automatic indentation of output streams.
• [`CGAL::IO::Basic_color_streambuf`](https://doc.cgal.org/6.2/Stream_support/classCGAL_1_1IO_1_1Basic__color__streambuf.html) and [`CGAL::IO::Basic_color_stream_guard`](https://doc.cgal.org/6.2/Stream_support/classCGAL_1_1IO_1_1Basic__color__stream__guard.html) for ANSI color support in terminal output.

📋 General Changes

• The new list of supported compilers is:
• Visual C++ 15.9, 16.10, 17.0 (from Visual Studio 2017, 2019 and 2022) or later
• Gnu g++ 12.2.0 or later (on Linux)
• LLVM Clang version 20.1.6 or later (on Linux)
• Apple Clang compiler versions 12.0.5 and 12.0.5 (on macOS)
• The minimal supported version of Boost is now 1.74.0.

✨ [3D Constrained Triangulations](https://doc.cgal.org/6.1/Manual/packages.html#PkgConstrainedTriangulation3) (new package)

• This package implements the construction of a 3D Constrained Delaunay triangulation. This triangulation is a generalization of a 3D Delaunay Triangulation which conforms to the set of faces of a 3D piecewise linear complex (PLC), ensuring that these faces are part of the triangulation. As not all PLCs are tetrahedralizable, the algorithm may insert Steiner points to construct the constrained triangulation. The main entry point is the function [`CGAL::make_conforming_constrained_Delaunay_triangulation_3()`](https://doc.cgal.org/6.1/Constrained_triangulation_3/group__PkgConstrainedTriangulation3FunctionsPolygonSoupOrMesh.html).

✨ [3D Isosurfacing](https://doc.cgal.org/6.1/Manual/packages.html#PkgIsosurfacing3) (new package)

• This package provides algorithms to extract isosurfaces from scalar fields. The algorithms provided in this first version include Marching Cubes, Topologically Correct Marching Cubes, and Dual Contouring. The algorithm is generic with respect to the scalar field representation (implicit function, discrete values, …) and the discretization data structure (Cartesian grid, octree, …). The output is an indexed face set that stores an isosurface in the form of a surface mesh.

✨ [dD Fréchet Distance](https://doc.cgal.org/6.1/Manual/packages.html#PkgFrechetDistance) (new package)

• This package provides functions for computing the Fréchet distance of polylines in any dimension under the Euclidean metric.

✨ [2D Triangulations on Hyperbolic Surfaces](https://doc.cgal.org/6.1/Manual/packages.html#PkgHyperbolicSurfaceTriangulation2) (new package)

• This package enables building and handling triangulations of closed orientable hyperbolic surfaces. It offers functions for the generation of the triangulation from a convex fundamental domain, the Delaunay flip algorithm, and the construction of a portion of the lift of the triangulation in the Poincaré disk. A method is offered that generates such domains in genus two.
• See also the associated [news entry](https://www.cgal.org/2025/06/24/triangulations-on-hyperbolic-surfaces/).

📝 [Polygon Repair](https://doc.cgal.org/6.1/Manual/packages.html#PkgPolygonRepair)

• Added the [non-zero rule](https://doc.cgal.org/6.1/Polygon_repair/structCGAL_1_1Polygon__repair_1_1Non__zero__rule.html) (areas with non-zero winding number are kept), as well as two functions to compute the conservative inner and outer hull of similar polygons:
• [`CGAL::Polygon_repair::join()`](https://doc.cgal.org/6.1/Polygon_repair/group__PkgPolygonRepairFunctions.html#gad5b959666d952392c0e3b8d4b1b1847a)
• [`CGAL::Polygon_repair::intersect()`](https://doc.cgal.org/6.1/Polygon_repair/group__PkgPolygonRepairFunctions.html#ga780e31115643e3d0b406349b56c9f3d5)
• See also the associated [news entry](https://www.cgal.org/2025/05/22/Polygon_repair/).

📝 [Polygon Mesh Processing](https://doc.cgal.org/6.1/Manual/packages.html#PkgPolygonMeshProcessing)

• Added the parameter `apply_iterative_snap_rounding` to the function [`CGAL::Polygon_mesh_processing::autorefine_triangle_soup()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__corefinement__grp.html#gaf7747d676c459d9e5da9b13be7d12bb5). When set to `true`, the coordinates are rounded to fit in double and may perform additional subdivisions to ensure the output is free of self-intersections. See also the associated [news entry](https://www.cgal.org/2025/06/13/autorefine-and-snap/).
• Added the function [`CGAL::Polygon_mesh_processing::approximated_centroidal_Voronoi_diagram_remeshing()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#gaed23e63b12c7fe8268927d17b4d379f1) to remesh triangle meshes. This remeshing algorithm uses clustering on polygonal meshes as to approximate a Centroidal Voronoi Diagram construction, and can move vertices as to recover sharp features and corners. See also the associated [news entry](https://www.cgal.org/2025/05/22/Surface_remeshing/).
• New implementation of [`CGAL::Polygon_mesh_processing::clip()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__corefinement__grp.html#ga2c73d3460872e601f84a03f58dd069ae) and [`CGAL::Polygon_mesh_processing::split()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__corefinement__grp.html#ga6738052411a4d548a5b375f11b913924) with a plane as clipper that is much faster and is now able to handle non-triangulated surface meshes. See also the associated [news entry](https://www.cgal.org/2025/06/06/new_clip/).
• Added the function [`CGAL::Polygon_mesh_processing::refine_with_plane()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__corefinement__grp.html#gacb9d68fa4dea8fd03ec53b56a16d6fc6), which enables users to refine a mesh with its intersection with a plane.
• Added a function in the [visitor of the corefinement based methods](https://doc.cgal.org/6.1/Polygon_mesh_processing/classPMPCorefinementVisitor.html) to trace faces in the output meshes which correspond to coplanar faces of the input.
• Added the function [`CGAL::Polygon_mesh_processing::discrete_mean_curvature()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__measure__grp.html#ga1a31fa9412b4643dc7202a54246db78b) and [`CGAL::Polygon_mesh_processing::discrete_Gaussian_curvature()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__measure__grp.html#ga11a2d646d4636605d185653bff5bbbbb) to evaluate the discrete curvature at a vertex of a mesh.
• Added the function [`CGAL::Polygon_mesh_processing::angle_sum()`](https://doc.cgal.org/6.1/Polygon_mesh_processing/group__PMP__measure__grp.html#ga25d3836c21931610cf76b6716a06254c) to compute the sum of the angles around a vertex.

📝 [Point Set Processing](https://doc.cgal.org/6.1/Manual/packages.html#PkgPointSetProcessing3)

• Added [`CGAL::poisson_eliminate()`](https://doc.cgal.org/6.1/Point_set_processing_3/group__PkgPointSetProcessing3Algorithms.html#ga2d73d46ca766656a219bf5e6045b837a), which can be used to downsample a point cloud to a target size while providing Poisson disk property, i.e., a larger minimal distance between points.

📝 [CGAL and the Boost Graph Library (BGL)](https://doc.cgal.org/6.1/Manual/packages.html#PkgBGL)

• Added the function [`dijkstra_shortest_path()`](https://doc.cgal.org/6.1/BGL/group__PkgBGLTraversal.html#gaa4058482db0089886b84a8c6a341e528), which can be used to compute the geometrically shortest sequence of halfedges between two vertices.
• Added the function [`CGAL::Euler::remove_degree_2_vertex()`](https://doc.cgal.org/6.1/BGL/group__PkgBGLEulerOperations.html#gab3455663b7db4624529e54ae3ce2387c), which enables users to remove vertices which have exactly two incident edges.

📝 [2D Arrangements](https://doc.cgal.org/6.1/Manual/packages.html#PkgArrangementOnSurface2)

• Breaking change: Renamed the concept `AosApproximateTraits_2` to [`AosApproximatePointTraits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classAosApproximatePointTraits__2.html) to make room for the new concept [`AosApproximateTraits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classAosApproximateTraits__2.html). This concept requires the provision of a functor called `Approximate_2` that has an operator that approximates the coordinates of a point.
• Breaking change: The concept [`AosApproximateTraits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classAosApproximateTraits__2.html) now refines the concept [`AosApproximatePointTraits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classAosApproximatePointTraits__2.html) and requires the provision of a functor called `Approximate_2`. In addition to an operator that approximates the coordinates of a point, it also requires the provision of (i) an operator that approximates a points, and (ii) an operator that approximates a curve.
• Renamed the prefix of the names of all concepts in the Arrangement_on_surface_2 package from “Arrangement” to “Aos”.
• Introduced two traits decorators, namely [`CGAL::Arr_tracing_traits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classCGAL_1_1Arr__tracing__traits__2.html) and [`CGAL::Arr_counting_traits_2`](https://doc.cgal.org/6.1/Arrangement_on_surface_2/classCGAL_1_1Arr__counting__traits__2.html), which can be used to extract debugging and informative metadata about the traits in use while a program is being executed.
• Fixed the Landmark point-location strategy so that it can be applied to arrangements on a sphere.
• Fixed a bug in the extensions of vertex and halfedge types of the DCEL when used to instantiate Arrangement_with_history_2 or similar arrangement classes that derive from Arrangement_2.
• Fixed `do_intersect()` of a 2D Arrangement with a curve.

📦 Triangulations

• All triangulations now offer the functions `point(Vertex_handle)` and `point(Simplex, int)`, which enables users to access the geometric position of a vertex and of the i-th vertex of a simplex of a triangulation.

📝 [Poisson Surface Reconstruction](https://doc.cgal.org/6.1/Manual/packages.html#PkgPoissonSurfaceReconstruction3)

• Added a new mesh domain `Poisson_mesh_domain_3` that integrates some optimizations from the deprecated 3D Surface Mesh Generation package.

📝 [2D Triangulations](https://doc.cgal.org/6.1/Manual/packages.html#PkgTriangulation2)

• Breaking change: In the class template [`Constrained_triangulation_plus_2`](https://doc.cgal.org/6.1/Triangulation_2/classCGAL_1_1Constrained__triangulation__plus__2.html), the value type of the range returned by [`subconstraints()`](https://doc.cgal.org/6.1/Triangulation_2/classCGAL_1_1Constrained__triangulation__plus__2.html#af25114a7e1675194367f8f9de9de90d2) has changed from `const std::pair<const Subconstraint, std::list<Context>*>` to `Subconstraint`. The old range type is now returned by a new function named `subconstraints_and_contexts()`.

📝 [3D Mesh Generation](https://doc.cgal.org/6.1/Manual/packages.html#PkgMesh3)

• Added two new meshing parameters that enable custom mesh initialization:
• [`initial_points_generator`](https://doc.cgal.org/6.1/Mesh_3/group__PkgMesh3Parameters.html#gaf53777b83f1b2f3e7d49275dbab6e46b): enables the user to specify a functor that generates initial points,
• [`initial_points`](https://doc.cgal.org/6.1/Mesh_3/group__PkgMesh3Parameters.html#gaf26d164d1845dcd66dc4861b6920b5ec): enables the user to specify a `Range` of initial points.
• Added a new meshing parameter [`surface_only`](https://doc.cgal.org/6.1/Mesh_3/group__PkgMesh3Parameters.html#gaa2618c09b6117d7caab12dccca16ee58), which can be used to improve performance when only surface mesh generation is sought.
• Added a new mesh domain [`Poisson_mesh_domain_3`](https://doc.cgal.org/6.1/Poisson_surface_reconstruction_3/classCGAL_1_1Poisson__mesh__domain__3.html), which should be used when generating a mesh from a Poisson surface obtained with the package [Poisson Surface Reconstruction](https://doc.cgal.org/6.1/Manual/packages.html#PkgPoissonSurfaceReconstruction3). This mesh domain re-integrates some optimizations for Poisson surface mesh generation that were lost when the package [3D Mesh Generation](https://doc.cgal.org/6.1/Manual/packages.html#PkgMesh3) had to be replaced instead of the deprecated package [3D Surface Mesh Generation](https://doc.cgal.org/latest/Manual/packages.html#PkgSurfaceMesher3).

📝 [3D Subdivision Methods](https://doc.cgal.org/6.1/Manual/packages.html#PkgSurfaceSubdivisionMethod3)

• Added a new named parameter for [`CGAL::Subdivision_method_3::Loop_subdivision()`](https://doc.cgal.org/6.1/Subdivision_method_3/group__PkgSurfaceSubdivisionMethod3Functions.html#gafa1e441c4e07eb06e1f6efecef7ff268) and [`CGAL::Subdivision_method_3::CatmullClark_subdivision()`](https://doc.cgal.org/6.1/Subdivision_method_3/group__PkgSurfaceSubdivisionMethod3Functions.html#ga8e6c8dd3c26d7a27c070b3a091684679), which enables users to subdivide a mesh without modifying its geometry.

📝 [Algebraic Kernel](https://doc.cgal.org/6.1/Manual/packages.html#PkgAlgebraicKernelD)

• Breaking change: Classes based on the RS Library are no longer provided.

📋 General Changes

• CGAL 6.0 is the first release of CGAL that requires a C++ compiler with the support of C++17 or later. The new list of supported compilers is:
• Visual C++ 15.9, 16.10, 17.0 (from Visual Studio 2017, 2019 and 2022) or later
• Gnu g++ 11.4.0 or later (on Linux or macOS)
• LLVM Clang version 15.0.7 or later (on Linux)
• Apple Clang compiler versions 10.0.1, 12.0.5, and 15.0.0 (on macOS)
• The minimal supported version of Boost is now 1.72.0.
• GMP/MPFR are no longer mandatory to use CGAL, [Boost.Multiprecision](https://www.boost.org/doc/libs/1_72_0/libs/multiprecision/doc/html/index.html). can be used instead.
• The CGAL `Core` library is no longer based on GMP, but on [Boost.Multiprecision](https://www.boost.org/doc/libs/1_72_0/libs/multiprecision/doc/html/index.html). Either GMP backend or Boost backend can be used.
• + 5 more

✨ [Kinetic Space Partition](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSpacePartition) (new package)

• This package implements kinetic space partition: based on a set of planar input shapes, the bounding box of the input data is split into convex volumes. The complexity of the partition can be adjusted with a single parameter.

✨ [Kinetic Surface Reconstruction](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSurfaceReconstruction) (new package)

• The package implements a piece-wise planar surface reconstruction pipeline from point clouds combining methods from the [Shape Detection](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeDetection), [Shape Regularization](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeRegularization) and [Kinetic Shape Partition](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSpacePartition) packages and graph-cut to reconstruct surfaces from point clouds.

✨ [Basic Viewer](https://doc.cgal.org/6.0/Basic_viewer/index.html#Chapter_Basic_viewer) (new package)

• The basic viewer package provides interactive visualization for most CGAL packages, such as [2D Arrangements](https://doc.cgal.org/6.0/Manual/packages.html#PkgArrangementOnSurface2), [2D Regularized Boolean Set-Operations](https://doc.cgal.org/6.0/Manual/packages.html#PkgBooleanSetOperations2), [Linear Cell Complex](https://doc.cgal.org/6.0/Manual/packages.html#PkgLinearCellComplex), [3D Boolean Operations on Nef Polyhedra](https://doc.cgal.org/6.0/Manual/packages.html#PkgNef3), [2D Periodic Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgPeriodic2Triangulation2), [3D Point Set](https://doc.cgal.org/6.0/Manual/packages.html#PkgPointSet3), [2D Polygons](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygon2), [3D Polyhedral Surface](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolyhedron), [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/6.0/Manual/packages.html#PkgStraightSkeleton2), [Surface Mesh](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesh), [2D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation2), [3D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation3), [2D Voronoi Diagrams](https://doc.cgal.org/6.0/Manual/packages.html#PkgVoronoiDiagram2), and more. The most simple use case of the basic viewer is the call of the global `CGAL::draw()` function. There is one such `draw()` function for each CGAL package that has a basic viewer. Such a call opens an interactive window showing the given model and allowing to navigate in the scene, show or hide some specific cells, show the interior of the model if any, etc. The `Basic_viewer` is based on Qt6.

✨ [Polygon Repair](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygonRepair) (new package)

• This package provides algorithms to repair 2D polygons, polygons with holes, and multipolygons with holes, by selecting faces of the arrangement of the input using the odd-even heuristic.

📝 [2D and 3D Linear Geometry Kernel](https://doc.cgal.org/6.0/Manual/packages.html#PkgKernel23)

• Breaking change: Replaced all instances of `boost::variant` with `std::variant` in the intersection functions.
• Breaking change: Replaced all instances of `boost::optional` with `std::optional` in the intersection functions.

📝 [3D Polyhedral Surface](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolyhedron)

• The demo of this package, also known as “Polyhedron Demo” has been renamed “CGAL Lab” and moved to its own package (“Lab”).

📝 [2D and 3D Fast Intersection and Distance Computation (AABB Tree)](https://doc.cgal.org/6.0/Manual/packages.html#PkgAABBTree)

• The AABB tree can now be used with 2D or 3D primitives:
• The concepts `AABBGeomTraits` and `AABBRayIntersectionGeomTraits` have been replaced by [`AABBGeomTraits_3`](https://doc.cgal.org/6.0/AABB_tree/classAABBGeomTraits__3.html) and by [`AABBRayIntersectionGeomTraits_3`](https://doc.cgal.org/6.0/AABB_tree/classAABBRayIntersectionGeomTraits__3.html), respectively.
• The concepts [`AABBGeomTraits_2`](https://doc.cgal.org/6.0/AABB_tree/classAABBGeomTraits__2.html) and [`AABBRayIntersectionGeomTraits_2`](https://doc.cgal.org/6.0/AABB_tree/classAABBRayIntersectionGeomTraits__2.html) have been introduced, as the 2D counterparts.
• The class [`CGAL::AABB_traits`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#ga764f0fc59c96355877536810aa1aca5b) is deprecated and replaced by [`CGAL::AABB_traits_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__traits__3.html).
• The class [`CGAL::AABB_traits_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__traits__2.html) is introduced as the 2D counterpart.
• The class [`CGAL::AABB_segment_primitive`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#gad0acfd5c4a3c081b7570cc6bd4594c8d) has been deprecated and replaced by the class [`CGAL::AABB_segment_primitive_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__segment__primitive__3.html).
• The class [`CGAL::AABB_triangle_primitive`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#ga54a56f01dc8024624f7d83ee0a01add0) has been deprecated and replaced by the class [`CGAL::AABB_triangle_primitive_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__triangle__primitive__3.html).
• The following 2D primitive classes have been added: [`CGAL::AABB_segment_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__segment__primitive__2.html), [`CGAL::AABB_polyline_segment_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__polyline__segment__primitive__2.html), [`CGAL::AABB_triangle_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__triangle__primitive__2.html), [`CGAL::AABB_indexed_triangle_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__indexed__triangle__primitive__2.html).
• + 2 more

📝 [2D Arrangements](https://doc.cgal.org/6.0/Manual/packages.html#PkgArrangementOnSurface2)

• Breaking change: Replaced all instances of `boost::variant` with `std::variant`.
• Breaking change: The type of the result of point location queries has been changed to `std::variant`. Support for the old macro `CGAL_ARR_POINT_LOCATION_VERSION` has been removed.
• Breaking change: Eliminated the error-prone C-type casting that was used to define observers. In general, backward compatibility was maintained; however, the class template [`CGAL::Arr_observer`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/group__PkgArrangementOnSurface2Ref.html#ga8019f986f5469920136c4b92290b7b1b) has been replaced by an alias template. (The class `CGAL::Arr_observer` was renamed to [`CGAL::Aos_observer`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/classCGAL_1_1Aos__observer.html)).
• Introduced [`Arr_dcel`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/classCGAL_1_1Arr__dcel.html), which essentially replaces the former `CGAL::Arr_default_dcel`. Backward compatibility was maintained by the introduction of the alias template [`CGAL::Arr_default_dcel`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/group__PkgArrangementOnSurface2DCEL.html#gaf9635869a3794a46d7dcfce63d7de2a6). `CGAL::Arr_dcel`, as opposed to the former `CGAL::Arr_default_dcel` is templated (in addition to the geometry traits) by `Vertex`, `Halfedge`, and `Face` template parameters, and they have default type values. All this enables the layered extension of DCEL records.
• Fixed a bug in the zone construction code applied to arrangements of geodesic arcs on a sphere, when inserting an arc that lies on the identification curve.
• Introduced a new interactive program that demonstrates 2D arrangements embedded on the sphere called `earth`. The program (i) reads a database of all administrative boundaries of the countries in the world, (ii) displays the globe with all countries and land covered by water (which is land not covered by countries) on a window, and (ii) enables interaction with the user.

📝 [3D Envelopes](https://doc.cgal.org/6.0/Manual/packages.html#PkgEnvelope3)

• Breaking change: [`Construct_projected_boundary_2`](https://doc.cgal.org/6.0/Envelope_3/classEnvelopeTraits__3.html#ac7b8f72870f0572834a0a3de62c67bc1) in [`EnvelopeTraits_3`](https://doc.cgal.org/6.0/Envelope_3/classEnvelopeTraits__3.html) now uses `std::variant` instead of [`CGAL::Object`](https://doc.cgal.org/6.0/STL_Extension/classCGAL_1_1Object.html).
• Passed the base class of [`CGAL::Env_plane_traits_3`](https://doc.cgal.org/6.0/Envelope_3/classCGAL_1_1Env__plane__traits__3.html) as a template parameter with a default value (being the 2D arrangement linear traits). Similarly, passed the base class of `CGAL::Env_triangle_traits_3` as a template parameter with a default value (being the 2D arrangement segment traits).

📝 [Combinatorial Maps](https://doc.cgal.org/6.0/Manual/packages.html#PkgCombinatorialMaps) and [Generalized Maps](https://doc.cgal.org/6.0/Manual/packages.html#PkgGeneralizedMaps)

• Added the function [`insert_cell_1_between_two_cells_2()`](https://doc.cgal.org/6.0/Combinatorial_map/classGenericMap.html#aa29570a0812094c7876e24a228373f12) to the [`GenericMap`](https://doc.cgal.org/6.0/Combinatorial_map/classGenericMap.html) concept, which enables users to insert an edge between two different faces in order to create faces with holes.

📝 [Quadtrees, Octrees, and Orthtrees](https://doc.cgal.org/6.0/Manual/packages.html#PkgOrthtree)

• Breaking change:
• Node splitting behavior and per-node data are now customizable via the Traits class.
• Nodes are now stored as a property map, with properties of each node accessed by index.
• Nearest neighbors functions only work for Orthtrees which provide the necessary functionality.

📝 [CGAL and the Boost Graph Library (BGL)](https://doc.cgal.org/6.0/Manual/packages.html#PkgBGL)

• Added the function [`CGAL::remove_all_elements()`](https://doc.cgal.org/6.0/BGL/group__PkgBGLHelperFct.html#gac7e199820c95ed1fc6ab536750749358), which removes vertices, halfedges, and faces without collecting garbage and without removing properties.
• [Dynamic property maps](https://doc.cgal.org/6.0/BGL/group__PkgBGLPropertiesDynamic.html) can now have a default value.
• The class [`CGAL::Face_filtered_graph`](https://doc.cgal.org/6.0/BGL/structCGAL_1_1Face__filtered__graph.html) now supports patch IDs of any type and not just `faces_size_type`. The only requirement is that the type is hashable.

📝 [Polygon Mesh Processing](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygonMeshProcessing)

• Added the function [`CGAL::Polygon_mesh_processing::autorefine_triangle_soup()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corefinement__grp.html#gaec85370aa0b2acc0919e5f8406cfb74c), which can be used to refine a soup of triangles such that no pair of triangles intersects in their interiors. Also added, the function [`CGAL::Polygon_mesh_processing::autorefine()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corefinement__grp.html#ga3e3a0a82b6c04bdc3a6c070e8da4aed5) operating directly on a triangle mesh and updating it using the aforementioned function on a triangle soup.
• Added the class [`CGAL::Corefinement::Non_manifold_output_visitor`](https://doc.cgal.org/6.0/Polygon_mesh_processing/structCGAL_1_1Polygon__mesh__processing_1_1Corefinement_1_1Non__manifold__output__visitor.html), which can be used in corefinement based functions to deal with non-manifold outputs.
• Added the option to use a variable sizing field for [`CGAL::Polygon_mesh_processing::isotropic_remeshing()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga66cb01cf228ed22f0a2a474cfa2aeb3f), and a sizing function based on a measure of local curvature for adaptive remeshing.
• Added the function [`CGAL::Polygon_mesh_processing::interpolated_corrected_curvatures()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corrected__curvatures__grp.html#ga22665c9ce92aaedab07df1b05f20bdb2) which can be used to compute the mean and Gaussian curvatures, as well as the principal curvature and directions.
• Added the function [`CGAL::Polygon_mesh_processing::refine_mesh_at_isolevel()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#ga396505d5a60b5f6d29792b214fa59352) which can be used to refine a polygon mesh along an isocurve.
• Added the function [`CGAL::Polygon_mesh_processing::add_bbox()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#gabaf98d2fd9ae599ff1f3a5a6cde79cf3), which enables adding a tight or extended, triangulated or not, bounding box to a face graph.

📝 [2D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation2)

• Breaking change: the concept [`TriangulationTraits_2`](https://doc.cgal.org/6.0/Triangulation_2/classTriangulationTraits__2.html) now requires an additional functor `Compare_xy_2`.

📝 [3D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation3)

• Added three member functions [`vertices()`](https://doc.cgal.org/6.0/Triangulation_3/classCGAL_1_1Triangulation__3.html#a02faf334255e1ca8caa1a6f412533759) to the class [`CGAL::Triangulation_3`](https://doc.cgal.org/6.0/Triangulation_3/classCGAL_1_1Triangulation__3.html). Each of them returns an array containing the vertices of the given triangulation simplex.

📝 [dD Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulations)

• Breaking change: `CGAL::TDS_full_cell_mirror_storage_policy` is now unsupported in dimension larger than 127.
• Breaking change: Inserting multiple unweighted points in the same position now keeps the first one, instead of switching to the latest. This only affects custom point types where not all points in the same position are equivalent.

📝 [Tetrahedral Remeshing](https://doc.cgal.org/6.0/Manual/packages.html#PkgTetrahedralRemeshing)

• Added a sizing field as new parameter of [`CGAL::tetrahedral_isotropic_remeshing()`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/group__PkgTetrahedralRemeshingRef.html#ga263775c52eeb483a86a16aeb9eb31af0), which can be used to perform non-uniform and adaptive remeshing.
• Breaking change: The template parameters of [`CGAL::Tetrahedral_remeshing::Remeshing_cell_base_3`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/classCGAL_1_1Tetrahedral__remeshing_1_1Remeshing__cell__base__3.html) have been modified, reverting changes introduced in CGAL 5.6.
• Breaking change: The vertex base of [`CGAL::Tetrahedral_remeshing::Remeshing_vertex_base_3`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/classCGAL_1_1Tetrahedral__remeshing_1_1Remeshing__vertex__base__3.html) must now be a model of the concept [`SimplicialMeshVertexBase_3`](https://doc.cgal.org/6.0/SMDS_3/classSimplicialMeshVertexBase__3.html) (and not only [`TriangulationVertexBase_3`](https://doc.cgal.org/6.0/Triangulation_3/classTriangulationVertexBase__3.html)).

📝 [3D Simplicial Mesh Data Structure](https://doc.cgal.org/6.0/Manual/packages.html#PkgSMDS3)

• Breaking change: The template parameters of [`CGAL::Simplicial_mesh_cell_base_3`](https://doc.cgal.org/6.0/SMDS_3/classCGAL_1_1Simplicial__mesh__cell__base__3.html) have been modified to enable passing a geometric traits and a custom cell base class.

📝 [3D Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgMesh3)

• Breaking change: Removed the concept `TriangleAccessor`, the template parameter `TriangleAccessor`, as well as the class `Triangle_accessor`. These were no longer used for several releases.
• Breaking change: Removed the class templates `CGAL::Gray_image_mesh_domain_3`, `CGAL::Implicit_mesh_domain_3`, and `CGAL::Labeled_image_mesh_domain_3`, which were deprecated since CGAL-4.13.
• Added new meshing criterion `edge_distance`, an upper bound for the distance from the edge to the 1D feature.
• Breaking change: the concept `MeshEdgeCriteria_3` was modified to include the new meshing criterion `edge_distance`.

📝 [3D Surface Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesher3)

• This package is deprecated and the package [3D Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgMesh3) should be used instead.

📝 [Surface Mesh Parameterization](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMeshParameterization)

• Breaking change: The method [`CGAL::Surface_mesh_parameterization::LSCM_parameterizer_3`](https://doc.cgal.org/6.0/Surface_mesh_parameterization/classCGAL_1_1Surface__mesh__parameterization_1_1LSCM__parameterizer__3.html) now requires the Eigen library.
• Breaking change: CGAL no longer ships its own version of OpenNL.

📝 [Surface Mesh](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesh)

• Breaking change: The return type of [`CGAL::Surface_mesh::property_map()`](https://doc.cgal.org/6.0/Surface_mesh/classCGAL_1_1Surface__mesh.html#afc99c7ea179dc1c21a2ab59ed183184a) has been changed to `std::optional`.

📝 [3D Point Set](https://doc.cgal.org/6.0/Manual/packages.html#PkgPointSet3)

• Breaking change: The return type of [`CGAL::Point_set_3::property_map()`](https://doc.cgal.org/6.0/Point_set_3/classCGAL_1_1Point__set__3.html#a571ecc603cd32d78c7effaf86fe120ad) has been changed to `std::optional`.

📝 [Shape Detection](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeDetection)

• Breaking change: Replaced all instances of `boost::shared_ptr` with `std::shared_ptr`.

📝 [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/6.0/Manual/packages.html#PkgStraightSkeleton2)

• Breaking change: Replaced all instances of `boost::shared_ptr` with `std::shared_ptr`.
• Breaking change: Replaced all instances of `boost::optional` with `std::optional`.
• Full Changelog: https://github.com/CGAL/cgal/compare/v5.6.1...v6.0

📋 General Changes

• CGAL 6.0 is the first release of CGAL that requires a C++ compiler with the support of C++17 or later. The new list of supported compilers is:
• Visual C++ 15.9, 16.10, 17.0 (from Visual Studio 2017, 2019 and 2022) or later
• Gnu g++ 11.4.0 or later (on Linux or macOS)
• LLVM Clang version 15.0.7 or later (on Linux)
• Apple Clang compiler versions 10.0.1, 12.0.5, and 15.0.0 (on macOS)
• The minimal supported version of Boost is now 1.72.0.
• The CGAL `Core` library is no longer based on GMP, but on [Boost.Multiprecision](https://www.boost.org/doc/libs/1_72_0/libs/multiprecision/doc/html/index.html). Either GMP backend or Boost backend can be used.
• All demos are now based on Qt6.
• + 1 more

✨ [Kinetic Space Partition](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSpacePartition) (new package)

• This package implements kinetic space partition: based on a set of planar input shapes, the bounding box of the input data is split into convex volumes. The complexity of the partition can be adjusted with a single parameter.

✨ [Kinetic Surface Reconstruction](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSurfaceReconstruction) (new package)

• The package implements a piece-wise planar surface reconstruction pipeline from point clouds combining methods from the [Shape Detection](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeDetection), [Shape Regularization](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeRegularization) and [Kinetic Shape Partition](https://doc.cgal.org/6.0/Manual/packages.html#PkgKineticSpacePartition) packages and graph-cut to reconstruct surfaces from point clouds.

✨ [Basic Viewer](https://doc.cgal.org/6.0/Basic_viewer/index.html#Chapter_Basic_viewer) (new package)

• The basic viewer package provides interactive visualization for most CGAL packages, such as [2D Arrangements](https://doc.cgal.org/6.0/Manual/packages.html#PkgArrangementOnSurface2), [2D Regularized Boolean Set-Operations](https://doc.cgal.org/6.0/Manual/packages.html#PkgBooleanSetOperations2), [Linear Cell Complex](https://doc.cgal.org/6.0/Manual/packages.html#PkgLinearCellComplex), [3D Boolean Operations on Nef Polyhedra](https://doc.cgal.org/6.0/Manual/packages.html#PkgNef3), [2D Periodic Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgPeriodic2Triangulation2), [3D Point Set](https://doc.cgal.org/6.0/Manual/packages.html#PkgPointSet3), [2D Polygons](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygon2), [3D Polyhedral Surface](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolyhedron), [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/6.0/Manual/packages.html#PkgStraightSkeleton2), [Surface Mesh](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesh), [2D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation2), [3D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation3), [2D Voronoi Diagrams](https://doc.cgal.org/6.0/Manual/packages.html#PkgVoronoiDiagram2), and more. The most simple use case of the basic viewer is the call of the global `CGAL::draw()` function. There is one such `draw()` function for each CGAL package that has a basic viewer. Such a call opens an interactive window showing the given model and allowing to navigate in the scene, show or hide some specific cells, show the interior of the model if any, etc. The `Basic_viewer` is based on Qt6.

✨ [Polygon Repair](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygonRepair) (new package)

• This package provides algorithms to repair 2D polygons, polygons with holes, and multipolygons with holes, by selecting faces of the arrangement of the input using the odd-even heuristic.

📝 [2D and 3D Linear Geometry Kernel](https://doc.cgal.org/6.0/Manual/packages.html#PkgKernel23)

• Breaking change: Replaced all instances of `boost::variant` with `std::variant` in the intersection functions.
• Breaking change: Replaced all instances of `boost::optional` with `std::optional` in the intersection functions.

📝 [3D Polyhedral Surface](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolyhedron)

• The demo of this package, also known as “Polyhedron Demo” has been renamed “CGAL Lab” and moved to its own package (“Lab”).

📝 [2D and 3D Fast Intersection and Distance Computation (AABB Tree)](https://doc.cgal.org/6.0/Manual/packages.html#PkgAABBTree)

• The AABB tree can now be used with 2D or 3D primitives:
• The concepts `AABBGeomTraits` and `AABBRayIntersectionGeomTraits` have been replaced by [`AABBGeomTraits_3`](https://doc.cgal.org/6.0/AABB_tree/classAABBGeomTraits__3.html) and by [`AABBRayIntersectionGeomTraits_3`](https://doc.cgal.org/6.0/AABB_tree/classAABBRayIntersectionGeomTraits__3.html), respectively.
• The concepts [`AABBGeomTraits_2`](https://doc.cgal.org/6.0/AABB_tree/classAABBGeomTraits__2.html) and [`AABBRayIntersectionGeomTraits_2`](https://doc.cgal.org/6.0/AABB_tree/classAABBRayIntersectionGeomTraits__2.html) have been introduced, as the 2D counterparts.
• The class [`CGAL::AABB_traits`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#ga764f0fc59c96355877536810aa1aca5b) is deprecated and replaced by [`CGAL::AABB_traits_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__traits__3.html).
• The class [`CGAL::AABB_traits_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__traits__2.html) is introduced as the 2D counterpart.
• The class [`CGAL::AABB_segment_primitive`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#gad0acfd5c4a3c081b7570cc6bd4594c8d) has been deprecated and replaced by the class [`CGAL::AABB_segment_primitive_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__segment__primitive__3.html).
• The class [`CGAL::AABB_triangle_primitive`](https://doc.cgal.org/6.0/AABB_tree/group__PkgAABBTreeRef.html#ga54a56f01dc8024624f7d83ee0a01add0) has been deprecated and replaced by the class [`CGAL::AABB_triangle_primitive_3`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__triangle__primitive__3.html).
• The following 2D primitive classes have been added: [`CGAL::AABB_segment_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__segment__primitive__2.html), [`CGAL::AABB_polyline_segment_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__polyline__segment__primitive__2.html), [`CGAL::AABB_triangle_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__triangle__primitive__2.html), [`CGAL::AABB_indexed_triangle_primitive_2`](https://doc.cgal.org/6.0/AABB_tree/classCGAL_1_1AABB__indexed__triangle__primitive__2.html).
• + 2 more

📝 [2D Arrangements](https://doc.cgal.org/6.0/Manual/packages.html#PkgArrangementOnSurface2)

• Breaking change: Replaced all instances of `boost::variant` with `std::variant`.
• Breaking change: The type of the result of point location queries has been changed to `std::variant`. Support for the old macro `CGAL_ARR_POINT_LOCATION_VERSION` has been removed.
• Breaking change: Eliminated the error-prone C-type casting that was used to define observers. In general, backward compatibility was maintained; however, the class template [`CGAL::Arr_observer`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/group__PkgArrangementOnSurface2Ref.html#ga8019f986f5469920136c4b92290b7b1b) has been replaced by an alias template. (The class `CGAL::Arr_observer` was renamed to [`CGAL::Aos_observer`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/classCGAL_1_1Aos__observer.html)).
• Introduced [`Arr_dcel`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/classCGAL_1_1Arr__dcel.html), which essentially replaces the former `CGAL::Arr_default_dcel`. Backward compatibility was maintained by the introduction of the alias template [`CGAL::Arr_default_dcel`](https://doc.cgal.org/6.0/Arrangement_on_surface_2/group__PkgArrangementOnSurface2DCEL.html#gaf9635869a3794a46d7dcfce63d7de2a6). `CGAL::Arr_dcel`, as opposed to the former `CGAL::Arr_default_dcel` is templated (in addition to the geometry traits) by `Vertex`, `Halfedge`, and `Face` template parameters, and they have default type values. All this enables the layered extension of DCEL records.
• Fixed a bug in the zone construction code applied to arrangements of geodesic arcs on a sphere, when inserting an arc that lies on the identification curve.
• Introduced a new interactive program that demonstrates 2D arrangements embedded on the sphere called `earth`. The program (i) reads a database of all administrative boundaries of the countries in the world, (ii) displays the globe with all countries and land covered by water (which is land not covered by countries) on a window, and (ii) enables interaction with the user.

📝 [3D Envelopes](https://doc.cgal.org/6.0/Manual/packages.html#PkgEnvelope3)

• Breaking change: [`Construct_projected_boundary_2`](https://doc.cgal.org/6.0/Envelope_3/classEnvelopeTraits__3.html#ac7b8f72870f0572834a0a3de62c67bc1) in [`EnvelopeTraits_3`](https://doc.cgal.org/6.0/Envelope_3/classEnvelopeTraits__3.html) now uses `std::variant` instead of [`CGAL::Object`](https://doc.cgal.org/6.0/STL_Extension/classCGAL_1_1Object.html).
• Passed the base class of [`CGAL::Env_plane_traits_3`](https://doc.cgal.org/6.0/Envelope_3/classCGAL_1_1Env__plane__traits__3.html) as a template parameter with a default value (being the 2D arrangement linear traits). Similarly, passed the base class of `CGAL::Env_triangle_traits_3` as a template parameter with a default value (being the 2D arrangement segment traits).

📝 [Combinatorial Maps](https://doc.cgal.org/6.0/Manual/packages.html#PkgCombinatorialMaps) and [Generalized Maps](https://doc.cgal.org/6.0/Manual/packages.html#PkgGeneralizedMaps)

• Added the function [`insert_cell_1_between_two_cells_2()`](https://doc.cgal.org/6.0/Combinatorial_map/classGenericMap.html#aa29570a0812094c7876e24a228373f12) to the [`GenericMap`](https://doc.cgal.org/6.0/Combinatorial_map/classGenericMap.html) concept, which enables users to insert an edge between two different faces in order to create faces with holes.
• Added new meshing criterion `edge_distance`, an upper bound for the distance from the edge to the 1D feature.
• Breaking change: the concept `MeshEdgeCriteria_3` was modified to include the new meshing criterion `edge_distance`.

📝 [Quadtrees, Octrees, and Orthtrees](https://doc.cgal.org/6.0/Manual/packages.html#PkgOrthtree)

• Breaking change:
• Node splitting behavior and per-node data are now customizable via the Traits class.
• Nodes are now stored as a property map, with properties of each node accessed by index.
• Nearest neighbors functions only work for Orthtrees which provide the necessary functionality.

📝 [CGAL and the Boost Graph Library (BGL)](https://doc.cgal.org/6.0/Manual/packages.html#PkgBGL)

• Added the function [`CGAL::remove_all_elements()`](https://doc.cgal.org/6.0/BGL/group__PkgBGLHelperFct.html#gac7e199820c95ed1fc6ab536750749358), which removes vertices, halfedges, and faces without collecting garbage and without removing properties.
• [Dynamic property maps](https://doc.cgal.org/6.0/BGL/group__PkgBGLPropertiesDynamic.html) can now have a default value.
• The class [`CGAL::Face_filtered_graph`](https://doc.cgal.org/6.0/BGL/structCGAL_1_1Face__filtered__graph.html) now supports patch IDs of any type and not just `faces_size_type`. The only requirement is that the type is hashable.

📝 [Polygon Mesh Processing](https://doc.cgal.org/6.0/Manual/packages.html#PkgPolygonMeshProcessing)

• Added the function [`CGAL::Polygon_mesh_processing::autorefine_triangle_soup()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corefinement__grp.html#gaec85370aa0b2acc0919e5f8406cfb74c), which can be used to refine a soup of triangles such that no pair of triangles intersects in their interiors. Also added, the function [`CGAL::Polygon_mesh_processing::autorefine()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corefinement__grp.html#ga3e3a0a82b6c04bdc3a6c070e8da4aed5) operating directly on a triangle mesh and updating it using the aforementioned function on a triangle soup.
• Added the class [`CGAL::Corefinement::Non_manifold_output_visitor`](https://doc.cgal.org/6.0/Polygon_mesh_processing/structCGAL_1_1Polygon__mesh__processing_1_1Corefinement_1_1Non__manifold__output__visitor.html), which can be used in corefinement based functions to deal with non-manifold outputs.
• Added the option to use a variable sizing field for [`CGAL::Polygon_mesh_processing::isotropic_remeshing()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga66cb01cf228ed22f0a2a474cfa2aeb3f), and a sizing function based on a measure of local curvature for adaptive remeshing.
• Added the function [`CGAL::Polygon_mesh_processing::interpolated_corrected_curvatures()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PMP__corrected__curvatures__grp.html#ga22665c9ce92aaedab07df1b05f20bdb2) which can be used to compute the mean and Gaussian curvatures, as well as the principal curvature and directions.
• Added the function [`CGAL::Polygon_mesh_processing::refine_mesh_at_isolevel()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#ga396505d5a60b5f6d29792b214fa59352) which can be used to refine a polygon mesh along an isocurve.
• Added the function [`CGAL::Polygon_mesh_processing::add_bbox()`](https://doc.cgal.org/6.0/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#gabaf98d2fd9ae599ff1f3a5a6cde79cf3), which enables adding a tight or extended, triangulated or not, bounding box to a face graph.

📝 [2D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation2)

• Breaking change: the concept [`TriangulationTraits_2`](https://doc.cgal.org/6.0/Triangulation_2/classTriangulationTraits__2.html) now requires an additional functor `Compare_xy_2`.

📝 [3D Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulation3)

• Added three member functions [`vertices()`](https://doc.cgal.org/6.0/Triangulation_3/classCGAL_1_1Triangulation__3.html#a02faf334255e1ca8caa1a6f412533759) to the class [`CGAL::Triangulation_3`](https://doc.cgal.org/6.0/Triangulation_3/classCGAL_1_1Triangulation__3.html). Each of them returns an array containing the vertices of the given triangulation simplex.

📝 [dD Triangulations](https://doc.cgal.org/6.0/Manual/packages.html#PkgTriangulations)

• Breaking change: `CGAL::TDS_full_cell_mirror_storage_policy` is now unsupported in dimension larger than 127.
• Breaking change: Inserting multiple unweighted points in the same position now keeps the first one, instead of switching to the latest. This only affects custom point types where not all points in the same position are equivalent.

📝 [Tetrahedral Remeshing](https://doc.cgal.org/6.0/Manual/packages.html#PkgTetrahedralRemeshing)

• Added a sizing field as new parameter of [`CGAL::tetrahedral_isotropic_remeshing()`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/group__PkgTetrahedralRemeshingRef.html#ga263775c52eeb483a86a16aeb9eb31af0), which can be used to perform non-uniform and adaptive remeshing.
• Breaking change: The template parameters of [`CGAL::Tetrahedral_remeshing::Remeshing_cell_base_3`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/classCGAL_1_1Tetrahedral__remeshing_1_1Remeshing__cell__base__3.html) have been modified, reverting changes introduced in CGAL 5.6.
• Breaking change: The vertex base of [`CGAL::Tetrahedral_remeshing::Remeshing_vertex_base_3`](https://doc.cgal.org/6.0/Tetrahedral_remeshing/classCGAL_1_1Tetrahedral__remeshing_1_1Remeshing__vertex__base__3.html) must now be a model of the concept [`SimplicialMeshVertexBase_3`](https://doc.cgal.org/6.0/SMDS_3/classSimplicialMeshVertexBase__3.html) (and not only [`TriangulationVertexBase_3`](https://doc.cgal.org/6.0/Triangulation_3/classTriangulationVertexBase__3.html)).

📝 [3D Simplicial Mesh Data Structure](https://doc.cgal.org/6.0/Manual/packages.html#PkgSMDS3)

• Breaking change: The template parameters of [`CGAL::Simplicial_mesh_cell_base_3`](https://doc.cgal.org/6.0/SMDS_3/classCGAL_1_1Simplicial__mesh__cell__base__3.html) have been modified to enable passing a geometric traits and a custom cell base class.

📝 [3D Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgMesh3)

• Breaking change: Removed the concept `TriangleAccessor`, the template parameter `TriangleAccessor`, as well as the class `Triangle_accessor`. These were no longer used for several releases.
• Breaking change: Removed the class templates `CGAL::Gray_image_mesh_domain_3`, `CGAL::Implicit_mesh_domain_3`, and `CGAL::Labeled_image_mesh_domain_3`, which were deprecated since CGAL-4.13.

📝 [3D Surface Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesher3)

• This package is deprecated and the package [3D Mesh Generation](https://doc.cgal.org/6.0/Manual/packages.html#PkgMesh3) should be used instead.

📝 [Surface Mesh Parameterization](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMeshParameterization)

• Breaking change: The method [`CGAL::Surface_mesh_parameterization::LSCM_parameterizer_3`](https://doc.cgal.org/6.0/Surface_mesh_parameterization/classCGAL_1_1Surface__mesh__parameterization_1_1LSCM__parameterizer__3.html) now requires the Eigen library.
• Breaking change: CGAL no longer ships its own version of OpenNL.

📝 [Surface Mesh](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesh)

• Breaking change: The return type of [`CGAL::Surface_mesh::property_map()`](https://doc.cgal.org/6.0/Surface_mesh/classCGAL_1_1Surface__mesh.html#afc99c7ea179dc1c21a2ab59ed183184a) has been changed to `std::optional`.

📝 [3D Point Set](https://doc.cgal.org/6.0/Manual/packages.html#PkgPointSet3)

• Breaking change: The return type of [`CGAL::Point_set_3::property_map()`](https://doc.cgal.org/6.0/Point_set_3/classCGAL_1_1Point__set__3.html#a571ecc603cd32d78c7effaf86fe120ad) has been changed to `std::optional`.

📝 [Shape Detection](https://doc.cgal.org/6.0/Manual/packages.html#PkgShapeDetection)

• Breaking change: Replaced all instances of `boost::shared_ptr` with `std::shared_ptr`.

📝 [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/6.0/Manual/packages.html#PkgStraightSkeleton2)

• Breaking change: Replaced all instances of `boost::shared_ptr` with `std::shared_ptr`.
• Breaking change: Replaced all instances of `boost::optional` with `std::optional`.

📋 General Changes

• Breaking change: Package-specific assertions, preconditions, and postconditions (such as `CGAL_triangulation_assertion`) have been removed. Corresponding CGAL-wide versions (such as `CGAL_assertion`) should be used instead.

📝 [Shape Detection](https://doc.cgal.org/5.6/Manual/packages.html#PkgShapeDetection) (major changes)

• Breaking change: The region growing part of the package have been reworked to fix design issues introduced with the handling of `FaceGraph` models. In particular, the notion of `Item` has been introduced to reference an element in the input range of elements. Region maps now operates on `Item` and no longer on the value type of the input range.
• Breaking change: The method `update()` in the concept `RegionType` now returns a `Boolean` instead of `void`, that is used inside the class `Region_growing` for detecting if the input conditions for the new region are satisfied. This change affects only user-defined types of regions.
• Breaking change: The constructors of all models used together with the region growing algorithm now enable users to provide parameters through the [named parameters](https://doc.cgal.org/5.6/BGL/group__bgl__namedparameters.html) mechanism.
• All fitting classes in the region growing framework are now using better versions of the region conditions, more precise and faster, including the correct normal orientations.
• Added new models of the concept `RegionType` for getting linear regions in a set of 2D and 3D segments and on 2D and 3D polylines.
• Added the class `Polyline_graph` for extracting a set of polylines from a face graph, which splits this graph into a set of user-defined regions.
• Added new shapes to the Region Growing algorithm on a point set: circles in 2D, spheres in 3D, and cylinders in 3D.

📝 [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/5.6/Manual/packages.html#PkgStraightSkeleton2) (major changes)

• Added weighted straight skeletons: weighted straight skeletons are a generalization of straight skeletons. Contour edges are assigned a positive weight, which can be understood as assigning a speed to the wavefront spawned from the contour edge.
• Added straight skeleton extrusion: this CGAL package now implements the extrusion of weighted straight skeletons of polygons with holes. The output is a closed, combinatorially 2-manifold surface triangle mesh.
• See also the [news entry](https://www.cgal.org/2023/05/09/improved_straight_skeleton/).

📝 [2D and 3D Linear Geometry Kernel](https://doc.cgal.org/5.6/Manual/packages.html#PkgKernel23)

• Added the functor [`CompareAngle_3`](https://doc.cgal.org/5.6/Kernel_23/classKernel_1_1CompareAngle__3.html) to the concept [`Kernel`](https://doc.cgal.org/5.6/Kernel_23/classKernel.html) to compare an angle defined by three points to the cosinus of another angle.

📝 [Combinatorial Maps](https://doc.cgal.org/5.6/Manual/packages.html#PkgCombinatorialMaps), [Generalized Maps](https://doc.cgal.org/5.6/Manual/packages.html#PkgGeneralizedMaps), and [Linear Cell Complex](https://doc.cgal.org/5.6/Manual/packages.html#PkgLinearCellComplex)

• Added a version that uses indices instead of handles as dart and attribute descriptors. As the indices are integers convertible from and to `std::size_t`, they can be used as index into vectors which store properties. To use the index version, `Use_index` must be defined and be equal to `CGAL::Tag_true` in the item class.

📝 [Linear Cell Complex](https://doc.cgal.org/5.6/Manual/packages.html#PkgLinearCellComplex)

• Added the class [`Linear_cell_complex_incremental_builder_3`](https://doc.cgal.org/5.6/Linear_cell_complex/classCGAL_1_1Linear__cell__complex__incremental__builder__3.html).

📝 [2D Arrangements](https://doc.cgal.org/5.6/Manual/packages.html#PkgArrangementOnSurface2)

• Introduced an overload function template, namely `draw(arr)`, that renders arrangements based on the `Basic_viewer_qt` class template. As of now, only 2D arrangements on the plane induced by (i) segments, (ii) conics, and (iii) circular arcs or (linear) segments are supported.
• Improved the traits class template that handles conics, namely [`Arr_conic_traits_2`](https://doc.cgal.org/5.6/Arrangement_on_surface_2/classCGAL_1_1Arr__conic__traits__2.html). This includes the following: 1. Fixed a couple of bugs and slightly optimized some functions. 2. Introduced functionality that approximates conics with polylines. (This is used to draw conic curves.) 3. Breaking change: Changed the interface to generate conic curves. In the past, curves where generated directly using the constructors of the conic and x-monotone conic constructs. Now, they are constructed via function objects provided by the traits. This eliminates the constructions of temporary kernels. The old functionality is obsolete, but still supported for a limited number of versions. It depends on a static member function of the traits. In a future version this function will no longer be static, implying that the old functionality will no longer be supported.
• Introduced functionality that approximates circular segments with polylines. (This is used to draw conic curves.)

📝 [Polygon Mesh Processing](https://doc.cgal.org/5.6/Manual/packages.html#PkgPolygonMeshProcessing)

• Added functions [`CGAL::Polygon_mesh_processing::region_growing_of_planes_on_faces()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#ga50dcd2f6295f584d2e378b57290ae2af) and [`CGAL::Polygon_mesh_processing::detect_corners_of_regions()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#gac8e445730d718a2fc49604e865017d2e), which enable partitioning a mesh into planar regions using the region growing algorithm from the [Shape Detection](https://doc.cgal.org/5.6/Manual/packages.html#PkgShapeDetection) package.
• Added the functions [`CGAL::Polygon_mesh_processing::remesh_planar_patches()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga7fca6fa2db94560ab6d32e6a77fc35b6) and [`CGAL::Polygon_mesh_processing::remesh_almost_planar_patches()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga0e6da479548199a5d82c3cf0ed36e8a0), which can be used to remesh patches of coplanar faces in a mesh.
• Added the function [`CGAL::Polygon_mesh_processing::surface_Delaunay_remeshing()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#gaff62f9415d2fe96d1d3095351f156ced), which can be used to remesh a surface triangle mesh using the Delaunay refinement algorithm from the [3D Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3) package.
• Added the function [`CGAL::Polygon_mesh_processing::remove_almost_degenerate_faces()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__geometric__repair__grp.html#ga48008d2b66de8a68a7068f29db15dad6), which can be used to remove badly shaped triangles faces in a mesh.
• Added the functions [`CGAL::Polygon_mesh_processing::does_triangle_soup_self_intersect()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__intersection__grp.html#ga4909920dc48b8285e69feb845feb1e53) and [`CGAL::Polygon_mesh_processing::triangle_soup_self_intersections()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__intersection__grp.html#ga1c5fee17bd0d92d5a2fba77ed94d4b4d) to identify and report self-intersections in a triangle soup, similarly to existing functions on triangle meshes.
• Added the function [`CGAL::Polygon_mesh_processing::triangulate_polygons()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga8b7db6aa8c3e79526b594739ba926d82), which allows users to triangulate polygon soups.
• Added a named parameter to [`CGAL::Polygon_mesh_processing::smooth_shape()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga57fa999abe8dc557003482444df2a189) to disable the scaling, which otherwise aims to compensate volume loss during smoothing.
• Deprecated the overloads of functions [`CGAL::Polygon_mesh_processing::triangulate_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga3abdf2d0558822e85f060966b69cae98), [`CGAL::Polygon_mesh_processing::triangulate_and_refine_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga9868fac4d9dca77462ad7828bc99d8a1), and [`CGAL::Polygon_mesh_processing::triangulate_refine_and_fair_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga18eac756a8f8e5d5f73e645fd4e26cad) which have output iterators for vertices and faces as parameter. They are replaced by overloads with two additional named parameters.

📝 [2D Convex Hulls](https://doc.cgal.org/5.6/Manual/packages.html#PkgConvexHull2)

• Breaking change: The concept [`ConvexHullTraits_2`](https://doc.cgal.org/5.6/Convex_hull_2/classConvexHullTraits__2.html) no longer requires the functor `Less_signed_distance_to_line_2`, but requires the functor `Compare_signed_distance_to_line_2` instead.
• The long-deprecated classes `Convex_hull_projective_xy_traits_2`, `Convex_hull_projective_xz_traits_2`, and `Convex_hull_projective_yz_traits_2` have been removed. Users should use [`Projection_traits_xy_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__xy__3.html), [`Projection_traits_xz_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__xz__3.html), and [`Projection_traits_yz_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__yz__3.html) instead.

📝 [2D Triangulations](https://doc.cgal.org/5.6/Manual/packages.html#PkgTriangulation2)

• Added the function [`CGAL::mark_domain_in_triangulation()`](https://doc.cgal.org/5.6/Triangulation_2/group__PkgTriangulation2Miscellaneous.html#ga0409755d0eb89100810230443a85e7eb) to mark faces connected with non-constrained edges as inside of the domain based on the nesting level.

📝 [2D Conforming Triangulations and Meshes](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh2)

• Added new overloads to the function [`write_VTU()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2IO.html), with property maps for specifying the domain.
• Deprecated usage of boost parameters in favor of function named parameters in [`CGAL::lloyd_optimize_mesh_2()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2Functions.html#gafeaf59d3fa014da287f8514913b38d05).
• Deprecated two overloads of the function [`refine_Delaunay_mesh()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2Functions.html), and replaced them with versions using function named parameters.

📝 [2D Hyperbolic Triangulations](https://doc.cgal.org/5.6/Manual/packages.html#PkgHyperbolicTriangulation2)

• Breaking change: the concept [`HyperbolicTriangulationFaceBase_2`](https://doc.cgal.org/5.6/Hyperbolic_triangulation_2/classHyperbolicTriangulationFaceBase__2.html) has been modified to better reflect the triangulation's requirements and avoid a conflict with the requirements described by the concept `TriangulationDataStructure_2::Face`. The model [`CGAL::Hyperbolic_triangulation_face_base_2`](https://doc.cgal.org/5.6/Hyperbolic_triangulation_2/classCGAL_1_1Hyperbolic__triangulation__face__base__2.html) has been adapted correspondingly.

✨ [3D Simplicial Mesh Data Structure](https://doc.cgal.org/5.6/Manual/packages.html#PkgSMDS3) (new package)

• This new package wraps all the existing code that deals with a [`MeshComplex_3InTriangulation_3`](https://doc.cgal.org/5.6/SMDS_3/classMeshComplex__3InTriangulation__3.html) to describe 3D simplicial meshes, and makes the data structure independent from the [tetrahedral mesh generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3) package.

📝 [Tetrahedral Remeshing](https://doc.cgal.org/5.6/Manual/packages.html#PkgTetrahedralRemeshing)

• Breaking change: The template parameters of [`CGAL::Tetrahedral_remeshing::Remeshing_vertex_base_3`](https://doc.cgal.org/5.6/Tetrahedral_remeshing/group__PkgTetrahedralRemeshingClasses.html#ga7ef4f8c0c1ed715c34389ea4ee851a92) and [`CGAL::Tetrahedral_remeshing::Remeshing_cell_base_3`](https://doc.cgal.org/5.6/Tetrahedral_remeshing/classCGAL_1_1Tetrahedral__remeshing_1_1Remeshing__cell__base__3.html) have been modified.

📝 [3D Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3)

• Added two new named parameters to the named constructor [`CGAL::create_labeled_image_mesh_domain()`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Labeled__mesh__domain__3.html#aec3f58e9883a8036a1b3e379df7d8fa9) for automatic detection and protection of 1D-curves that lie at the intersection of three or more subdomains extracted from labeled images.
• Added [`CGAL::Sizing_field_with_aabb_tree`](https://doc.cgal.org/5.6/Mesh_3/structCGAL_1_1Sizing__field__with__aabb__tree.html), a geometry-aware sizing field for feature edges in polyhedral domains.
• Added new meshing criterion [`edge_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) to avoid subdividing sharp edges that are shorter than a prescribed size bound.
• Added new meshing criteria [`facet_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) and [`cell_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) to prevent Delaunay refinement from creating simplices smaller than a prescribed bound.
• Deprecated usage of boost parameters in favor of function named parameters.

📝 [3D Periodic Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgPeriodic3Mesh3)

• Periodic Mesh Generation now supports non-cubic domains.
• Deprecated usage of boost parameters in favor of function named parameters.

📝 [Surface Mesh Simplification](https://doc.cgal.org/5.6/Manual/packages.html#PkgSurfaceMeshSimplification)

• The stop predicates [`Count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Count__stop__predicate.html) and [`Count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Count__ratio__stop__predicate.html) are renamed to [`Edge_count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Edge__count__stop__predicate.html) and [`Edge_count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Edge__count__ratio__stop__predicate.html). Older versions have been deprecated.
• Introduced [`Face_count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Face__count__stop__predicate.html) and [`Face_count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Face__count__ratio__stop__predicate.html), which can be used to stop the simplification algorithm based on a desired number of faces in the output, or a ratio between input and output face numbers.

📝 [2D Regularized Boolean Set Operations](https://doc.cgal.org/5.6/Manual/packages.html#PkgBooleanSetOperations2)

• Exposed all required member functions of the [`GeneralPolygonWithHoles_2`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html) concept (e.g., [`clear_outer_boundary()`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html#a9f5f035047505a2ccab3e68770f51bc6), [`clear_holes()`](https://cgal.geometryfactory.com/CGAL/doc/master/Polygon/classGeneralPolygonWithHoles__2.html#a2a507be648f127ac605da8c670ea2580), and [`clear()`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html#a2ca4d9b43cc9216c1b2cdb080a915944) ).

🐛 Known Bug

• MSVC 2015 is still supported by this version of CGAL, but the feature _Segment Cell Iterator_ of the class [`CGAL::Triangulation_3`](https://doc.cgal.org/5.6/Triangulation_3/classCGAL_1_1Triangulation__3.html) does not compile with MSVC 2015.

📋 General Changes

• Breaking change: Package-specific assertions, preconditions, and postconditions (such as `CGAL_triangulation_assertion`) have been removed. Corresponding CGAL-wide versions (such as `CGAL_assertion`) should be used instead.

📝 [Shape Detection](https://doc.cgal.org/5.6/Manual/packages.html#PkgShapeDetection) (major changes)

• Breaking change: The region growing part of the package have been reworked to fix design issues introduced with the handling of `FaceGraph` models. In particular, the notion of `Item` has been introduced to reference an element in the input range of elements. Region maps now operates on `Item` and no longer on the value type of the input range.
• Breaking change: The method `update()` in the concept `RegionType` now returns a `Boolean` instead of `void`, that is used inside the class `Region_growing` for detecting if the input conditions for the new region are satisfied. This change affects only user-defined types of regions.
• Breaking change: The constructors of all models used together with the region growing algorithm now enable users to provide parameters through the [named parameters](https://doc.cgal.org/5.6/BGL/group__bgl__namedparameters.html) mechanism.
• All fitting classes in the region growing framework are now using better versions of the region conditions, more precise and faster, including the correct normal orientations.
• Added new models of the concept `RegionType` for getting linear regions in a set of 2D and 3D segments and on 2D and 3D polylines.
• Added the class `Polyline_graph` for extracting a set of polylines from a face graph, which splits this graph into a set of user-defined regions.
• Added new shapes to the Region Growing algorithm on a point set: circles in 2D, spheres in 3D, and cylinders in 3D.

📝 [2D Straight Skeleton and Polygon Offsetting](https://doc.cgal.org/5.6/Manual/packages.html#PkgStraightSkeleton2) (major changes)

• Added weighted straight skeletons: weighted straight skeletons are a generalization of straight skeletons. Contour edges are assigned a positive weight, which can be understood as assigning a speed to the wavefront spawned from the contour edge.
• Added straight skeleton extrusion: this CGAL package now implements the extrusion of weighted straight skeletons of polygons with holes. The output is a closed, combinatorially 2-manifold surface triangle mesh.
• See also the [news entry](https://www.cgal.org/2023/05/09/improved_straight_skeleton/).

📝 [2D and 3D Linear Geometry Kernel](https://doc.cgal.org/5.6/Manual/packages.html#PkgKernel23)

• Added the functor [`CompareAngle_3`](https://doc.cgal.org/5.6/Kernel_23/classKernel_1_1CompareAngle__3.html) to the concept [`Kernel`](https://doc.cgal.org/5.6/Kernel_23/classKernel.html) to compare an angle defined by three points to the cosinus of another angle.

📝 [Combinatorial Maps](https://doc.cgal.org/5.6/Manual/packages.html#PkgCombinatorialMaps), [Generalized Maps](https://doc.cgal.org/5.6/Manual/packages.html#PkgGeneralizedMaps), and [Linear Cell Complex](https://doc.cgal.org/5.6/Manual/packages.html#PkgLinearCellComplex)

• Added a version that uses indices instead of handles as dart and attribute descriptors. As the indices are integers convertible from and to `std::size_t`, they can be used as index into vectors which store properties. To use the index version, `Use_index` must be defined and be equal to `CGAL::Tag_true` in the item class.

📝 [Linear Cell Complex](https://doc.cgal.org/5.6/Manual/packages.html#PkgLinearCellComplex)

• Added the class [`Linear_cell_complex_incremental_builder_3`](https://doc.cgal.org/5.6/Linear_cell_complex/classCGAL_1_1Linear__cell__complex__incremental__builder__3.html).

📝 [2D Arrangements](https://doc.cgal.org/5.6/Manual/packages.html#PkgArrangementOnSurface2)

• Introduced an overload function template, namely `draw(arr)`, that renders arrangements based on the `Basic_viewer_qt` class template. As of now, only 2D arrangements on the plane induced by (i) segments, (ii) conics, and (iii) circular arcs or (linear) segments are supported.
• Improved the traits class template that handles conics, namely [`Arr_conic_traits_2`](https://doc.cgal.org/5.6/Arrangement_on_surface_2/classCGAL_1_1Arr__conic__traits__2.html). This includes the following: 1. Fixed a couple of bugs and slightly optimized some functions. 2. Introduced functionality that approximates conics with polylines. (This is used to draw conic curves.) 3. Breaking change: Changed the interface to generate conic curves. In the past, curves where generated directly using the constructors of the conic and x-monotone conic constructs. Now, they are constructed via function objects provided by the traits. This eliminates the constructions of temporary kernels. The old functionality is obsolete, but still supported for a limited number of versions. It depends on a static member function of the traits. In a future version this function will no longer be static, implying that the old functionality will no longer be supported.
• Introduced functionality that approximates circular segments with polylines. (This is used to draw conic curves.)

📝 [Polygon Mesh Processing](https://doc.cgal.org/5.6/Manual/packages.html#PkgPolygonMeshProcessing)

• Added functions [`CGAL::Polygon_mesh_processing::region_growing_of_planes_on_faces()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#ga50dcd2f6295f584d2e378b57290ae2af) and [`CGAL::Polygon_mesh_processing::detect_corners_of_regions()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PkgPolygonMeshProcessingRef.html#gac8e445730d718a2fc49604e865017d2e), which enable partitioning a mesh into planar regions using the region growing algorithm from the [Shape Detection](https://doc.cgal.org/5.6/Manual/packages.html#PkgShapeDetection) package.
• Added the functions [`CGAL::Polygon_mesh_processing::remesh_planar_patches()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga7fca6fa2db94560ab6d32e6a77fc35b6) and [`CGAL::Polygon_mesh_processing::remesh_almost_planar_patches()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga0e6da479548199a5d82c3cf0ed36e8a0), which can be used to remesh patches of coplanar faces in a mesh.
• Added the function [`CGAL::Polygon_mesh_processing::surface_Delaunay_remeshing()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#gaff62f9415d2fe96d1d3095351f156ced), which can be used to remesh a surface triangle mesh using the Delaunay refinement algorithm from the [3D Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3) package.
• Added the function [`CGAL::Polygon_mesh_processing::remove_almost_degenerate_faces()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__geometric__repair__grp.html#ga48008d2b66de8a68a7068f29db15dad6), which can be used to remove badly shaped triangles faces in a mesh.
• Added the functions [`CGAL::Polygon_mesh_processing::does_triangle_soup_self_intersect()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__intersection__grp.html#ga4909920dc48b8285e69feb845feb1e53) and [`CGAL::Polygon_mesh_processing::triangle_soup_self_intersections()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__intersection__grp.html#ga1c5fee17bd0d92d5a2fba77ed94d4b4d) to identify and report self-intersections in a triangle soup, similarly to existing functions on triangle meshes.
• Added the function [`CGAL::Polygon_mesh_processing::triangulate_polygons()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga8b7db6aa8c3e79526b594739ba926d82), which allows users to triangulate polygon soups.
• Added a named parameter to [`CGAL::Polygon_mesh_processing::smooth_shape()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga57fa999abe8dc557003482444df2a189) to disable the scaling, which otherwise aims to compensate volume loss during smoothing.
• Deprecated the overloads of functions [`CGAL::Polygon_mesh_processing::triangulate_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga3abdf2d0558822e85f060966b69cae98), [`CGAL::Polygon_mesh_processing::triangulate_and_refine_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga9868fac4d9dca77462ad7828bc99d8a1), and [`CGAL::Polygon_mesh_processing::triangulate_refine_and_fair_hole()`](https://doc.cgal.org/5.6/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#ga18eac756a8f8e5d5f73e645fd4e26cad) which have output iterators for vertices and faces as parameter. They are replaced by overloads with two additional named parameters.

📝 [2D Convex Hulls](https://doc.cgal.org/5.6/Manual/packages.html#PkgConvexHull2)

• Breaking change: The concept [`ConvexHullTraits_2`](https://doc.cgal.org/5.6/Convex_hull_2/classConvexHullTraits__2.html) no longer requires the functor `Less_signed_distance_to_line_2`, but requires the functor `Compare_signed_distance_to_line_2` instead.
• The long-deprecated classes `Convex_hull_projective_xy_traits_2`, `Convex_hull_projective_xz_traits_2`, and `Convex_hull_projective_yz_traits_2` have been removed. Users should use [`Projection_traits_xy_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__xy__3.html), [`Projection_traits_xz_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__xz__3.html), and [`Projection_traits_yz_3`](https://doc.cgal.org/5.6/Kernel_23/classCGAL_1_1Projection__traits__yz__3.html) instead.

📝 [2D Triangulations](https://doc.cgal.org/5.6/Manual/packages.html#PkgTriangulation2)

• Added the function [`CGAL::mark_domain_in_triangulation()`](https://doc.cgal.org/5.6/Triangulation_2/group__PkgTriangulation2Miscellaneous.html#ga0409755d0eb89100810230443a85e7eb) to mark faces connected with non-constrained edges as inside of the domain based on the nesting level.

📝 [2D Conforming Triangulations and Meshes](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh2)

• Added new overloads to the function [`write_VTU()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2IO.html), with property maps for specifying the domain.
• Deprecated usage of boost parameters in favor of function named parameters in [`CGAL::lloyd_optimize_mesh_2()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2Functions.html#gafeaf59d3fa014da287f8514913b38d05).
• Deprecated two overloads of the function [`refine_Delaunay_mesh()`](https://doc.cgal.org/5.6/Mesh_2/group__PkgMesh2Functions.html), and replaced them with versions using function named parameters.

📝 [2D Hyperbolic Triangulations](https://doc.cgal.org/5.6/Manual/packages.html#PkgHyperbolicTriangulation2)

• Breaking change: the concept [`HyperbolicTriangulationFaceBase_2`](https://doc.cgal.org/5.6/Hyperbolic_triangulation_2/classHyperbolicTriangulationFaceBase__2.html) has been modified to better reflect the triangulation's requirements and avoid a conflict with the requirements described by the concept `TriangulationDataStructure_2::Face`. The model [`CGAL::Hyperbolic_triangulation_face_base_2`](https://doc.cgal.org/5.6/Hyperbolic_triangulation_2/classCGAL_1_1Hyperbolic__triangulation__face__base__2.html) has been adapted correspondingly.

✨ [3D Simplicial Mesh Data Structure](https://doc.cgal.org/5.6/Manual/packages.html#PkgSMDS3) (new package)

• This new package wraps all the existing code that deals with a [`MeshComplex_3InTriangulation_3`](https://doc.cgal.org/5.6/SMDS_3/classMeshComplex__3InTriangulation__3.html) to describe 3D simplicial meshes, and makes the data structure independent from the [tetrahedral mesh generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3) package.

📝 [3D Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgMesh3)

• Added two new named parameters to the named constructor [`CGAL::create_labeled_image_mesh_domain()`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Labeled__mesh__domain__3.html#aec3f58e9883a8036a1b3e379df7d8fa9) for automatic detection and protection of 1D-curves that lie at the intersection of three or more subdomains extracted from labeled images.
• Added [`CGAL::Sizing_field_with_aabb_tree`](https://doc.cgal.org/5.6/Mesh_3/structCGAL_1_1Sizing__field__with__aabb__tree.html), a geometry-aware sizing field for feature edges in polyhedral domains.
• Added new meshing criterion [`edge_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) to avoid subdividing sharp edges that are shorter than a prescribed size bound.
• Added new meshing criteria [`facet_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) and [`cell_min_size`](https://doc.cgal.org/5.6/Mesh_3/classCGAL_1_1Mesh__criteria__3.html#a5f1c2649cb7ea346a3b6a2a8724b4df1) to prevent Delaunay refinement from creating simplices smaller than a prescribed bound.
• Deprecated usage of boost parameters in favor of function named parameters.

📝 [3D Periodic Mesh Generation](https://doc.cgal.org/5.6/Manual/packages.html#PkgPeriodic3Mesh3)

• Periodic Mesh Generation now supports non-cubic domains.
• Deprecated usage of boost parameters in favor of function named parameters.

📝 [Surface Mesh Simplification](https://doc.cgal.org/5.6/Manual/packages.html#PkgSurfaceMeshSimplification)

• The stop predicates [`Count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Count__stop__predicate.html) and [`Count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Count__ratio__stop__predicate.html) are renamed to [`Edge_count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Edge__count__stop__predicate.html) and [`Edge_count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Edge__count__ratio__stop__predicate.html). Older versions have been deprecated.
• Introduced [`Face_count_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Face__count__stop__predicate.html) and [`Face_count_ratio_stop_predicate`](https://doc.cgal.org/5.6/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1Face__count__ratio__stop__predicate.html), which can be used to stop the simplification algorithm based on a desired number of faces in the output, or a ratio between input and output face numbers.

📝 [2D Regularized Boolean Set Operations](https://doc.cgal.org/5.6/Manual/packages.html#PkgBooleanSetOperations2)

• Exposed all required member functions of the [`GeneralPolygonWithHoles_2`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html) concept (e.g., [`clear_outer_boundary()`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html#a9f5f035047505a2ccab3e68770f51bc6), [`clear_holes()`](https://cgal.geometryfactory.com/CGAL/doc/master/Polygon/classGeneralPolygonWithHoles__2.html#a2a507be648f127ac605da8c670ea2580), and [`clear()`](https://doc.cgal.org/5.6/Polygon/classGeneralPolygonWithHoles__2.html#a2ca4d9b43cc9216c1b2cdb080a915944) ).

✨ [3D Alpha Wrapping (new package)](https://doc.cgal.org/5.5/Manual/packages.html#PkgAlphaWrap3)

• This component takes a 3D triangle mesh, soup, or point set as input, and generates a valid (watertight, intersection-free, and combinatorially 2-manifold) surface triangle mesh that contains the input.
• The algorithm proceeds by shrink-wrapping and refining a 3D Delaunay triangulation, starting from a loose bounding box of the input.
• to the input for complexity of the output.
• See also the [announcement page](https://www.cgal.org/2022/05/18/alpha_wrap/).

💥 [2D Straight Skeleton and Polygon Offsetting (breaking change)](https://doc.cgal.org/5.5/Manual/packages.html#PkgStraightSkeleton2)

• Fix the output of the function [CGAL::create_exterior_skeleton_and_offset_polygons_with_holes_2()](https://doc.cgal.org/5.5/Straight_skeleton_2/group__PkgStraightSkeleton2OffsetFunctions.html#gaa159f093e5d6d7fdb62c1660a44f95fe)
• to not take into account the offset of the outer frame.
• Fix the computation of the exterior offset of a polygon with holes that was not computing the offset of the holes

📝 [3D Convex Hulls](https://doc.cgal.org/5.5/Manual/packages.html#PkgConvexHull3)

• Added an [overload of the function `CGAL::convex_hull_3()`](https://doc.cgal.org/5.5/Convex_hull_3/group__PkgConvexHull3Functions.html#ga52fca4745c2ef0351063fbe66b035fd1), which writes the result in an indexed triangle set.

📝 [2D Polygons](https://doc.cgal.org/5.5/Manual/packages.html#PkgPolygon2)

• Add vertex, edge, and hole ranges.
• The concept [`GeneralPolygonWithHoles_2`](https://doc.cgal.org/5.5/Polygon/classGeneralPolygonWithHoles__2.html) now requires the nested type `Polygon_2` instead of `General_polygon_2`.

📝 [2D Regularized Boolean Set-Operations](https://doc.cgal.org/5.5/Manual/packages.html#PkgBooleanSetOperations2)

• The concept [`GeneralPolygonSetTraits_2`](https://doc.cgal.org/5.5/Boolean_set_operations_2/classGeneralPolygonSetTraits__2.html) now requires the nested type `Construct_polygon_with_holes_2` instead of `Construct_general_polygon_with_holes_2`.

📝 [Combinatorial Maps](https://doc.cgal.org/5.5/Manual/packages.html#PkgCombinatorialMaps)

• Removed old code deprecated in CGAL 4.9 and 4.10 (global functions, and information associated with darts).

📝 [2D Arrangements](https://doc.cgal.org/5.5/Manual/packages.html#PkgArrangementOnSurface2)

• Fixed the `intersect_2`, `compare_y_at_x_right`, and `compare_y_at_x_left` function objects of the traits class template [`Arr_geodesic_arc_on_sphere_traits_2`](https://doc.cgal.org/5.5/Arrangement_on_surface_2/classCGAL_1_1Arr__geodesic__arc__on__sphere__traits__2.html) that handles geodesic arcs on sphere and applied a small syntactical fix to the tracing traits.

📝 [Tetrahedral Mesh Generation](https://doc.cgal.org/5.5/Manual/packages.html#PkgMesh3)

• Added the function [`remove_isolated_vertices()`](https://doc.cgal.org/5.5/Mesh_3/classCGAL_1_1Mesh__complex__3__in__triangulation__3.html#ace57c4e777da457c6e33b4f6e89949ce) as a post-processing step for the tetrahedral mesh generation.

📝 [Polygon Mesh Processing](https://doc.cgal.org/5.5/Manual/packages.html#PkgPolygonMeshProcessing)

• Added the function [`CGAL::Polygon_mesh_processing::orient_triangle_soup_with_reference_triangle_soup()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__orientation__grp.html#ga855b1c55c201b91ab04eebd2811a87fd), which enables re-orienting the faces of a triangle soup based on the orientation of the nearest face in a reference triangle soup.
• Added the function [`CGAL::Polygon_mesh_processing::compatible_orientations()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__orientation__grp.html#ga9ac9b9434084b64f3304df636c3178a3), which enables to retrieve the (in)compatibility of orientations of faces from different connected components.
• Added the function [`CGAL::Polygon_mesh_processing::tangential_relaxation()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga136c659162e5360354db5879db7431b4), which applies an area-based tangential mesh smoothing to the vertices of a surface triangle mesh.
• Added the named parameter `visitor` to the function [`triangulate_hole()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#gad2d3c43bce0ef90a16530478196d7f42), which enables to track progress with callbacks.
• Added more functions in the [visitor of the corefinement based methods](https://doc.cgal.org/5.5/Polygon_mesh_processing/classPMPCorefinementVisitor.html) to track progress.

📝 [Surface Mesh Simplification](https://doc.cgal.org/5.5/Manual/packages.html#PkgSurfaceMeshSimplification)

• Introduced four variations of the Garland-Heckbert simplification algorithm based on the probabilistic approach of Trettner and Kobbelt (Fast and Robust QEF Minimization using Probabilistic Quadrics): [`GarlandHeckbert_plane_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__plane__policies.html), [`GarlandHeckbert_probabilistic_plane_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__probabilistic__plane__policies.html), [`GarlandHeckbert_triangle_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__triangle__policies.html), and [`GarlandHeckbert_probabilistic_triangle_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__probabilistic__triangle__policies.html).
• The class `GarlandHeckbert_policies` has been deprecated, `GarlandHeckbert_plane_policies` replaces it.

📝 [Point Set Processing](https://doc.cgal.org/5.5/Manual/packages.html#PkgPointSetProcessing3)

• A new optional named parameter, `min_points_per_cell` has been added to [`grid_simplify_point_set()`](https://doc.cgal.org/5.5/Point_set_processing_3/group__PkgPointSetProcessing3Algorithms.html#ga7757ef9b3900e42fde26f5a0ac56e20f). By adding a minimal number of points in a cell such that a point is retained, one can also filter out low density areas and outliers: in the case of densely sampled point clouds, this yields better results than using grid simplification and then outlier removal, while being very vast. The default value is `1` to keep the previous behavior as default.

📝 [dD Spatial Searching](https://doc.cgal.org/5.5/Manual/packages.html#PkgSpatialSearchingD)

• Added the member function [`write_graphviz()`](https://doc.cgal.org/5.5/Spatial_searching/classCGAL_1_1Kd__tree.html#ac2851b5cafb8d5cce0dc5fb107c8f13f) to the class `Kd_tree` that writes the tree in a stream in the [Graphviz](https://graphviz.org/) format.

📝 [CGAL and the Boost Graph Library (BGL)](https://doc.cgal.org/5.5/Manual/packages.html#PkgBGL)

• Added the function [`invert_selection()`](https://doc.cgal.org/5.5/BGL/structCGAL_1_1Face__filtered__graph.html#aa428541ebbdd35f9a6e9a3ffd60178df) in the class [`Face_filtered_graph`](https://doc.cgal.org/5.5/BGL/structCGAL_1_1Face__filtered__graph.html), which toggles the selected status of a graph: selected faces are deselected, and unselected faces are selected.

✨ [3D Alpha Wrapping (new package)](https://doc.cgal.org/5.5/Manual/packages.html#PkgAlphaWrap3)

• This component takes a 3D triangle mesh, soup, or point set as input, and generates a valid (watertight, intersection-free, and combinatorially 2-manifold) surface triangle mesh that contains the input.
• The algorithm proceeds by shrink-wrapping and refining a 3D Delaunay triangulation, starting from a loose bounding box of the input.
• to the input for complexity of the output.
• See also the [announcement page](https://www.cgal.org/2022/05/18/alpha_wrap/).

📝 [3D Convex Hulls](https://doc.cgal.org/5.5/Manual/packages.html#PkgConvexHull3)

• Added an [overload of the function `CGAL::convex_hull_3()`](https://doc.cgal.org/5.5/Convex_hull_3/group__PkgConvexHull3Functions.html#ga52fca4745c2ef0351063fbe66b035fd1), which writes the result in an indexed triangle set.

📝 [2D Polygons](https://doc.cgal.org/5.5/Manual/packages.html#PkgPolygon2)

• Add vertex, edge, and hole ranges.
• The concept [`GeneralPolygonWithHoles_2`](https://doc.cgal.org/5.5/Polygon/classGeneralPolygonWithHoles__2.html) now requires the nested type `Polygon_2` instead of `General_polygon_2`.

📝 [2D Regularized Boolean Set-Operations](https://doc.cgal.org/5.5/Manual/packages.html#PkgBooleanSetOperations2)

• The concept [`GeneralPolygonSetTraits_2`](https://doc.cgal.org/5.5/Boolean_set_operations_2/classGeneralPolygonSetTraits__2.html) now requires the nested type `Construct_polygon_with_holes_2` instead of `Construct_general_polygon_with_holes_2`.

📝 [Combinatorial Maps](https://doc.cgal.org/5.5/Manual/packages.html#PkgCombinatorialMaps)

• Removed old code deprecated in CGAL 4.9 and 4.10 (global functions, and information associated with darts).

📝 [2D Arrangements](https://doc.cgal.org/5.5/Manual/packages.html#PkgArrangementOnSurface2)

• Fixed the `intersect_2`, `compare_y_at_x_right`, and `compare_y_at_x_left` function objects of the traits class template [`Arr_geodesic_arc_on_sphere_traits_2`](https://doc.cgal.org/5.5/Arrangement_on_surface_2/classCGAL_1_1Arr__geodesic__arc__on__sphere__traits__2.html) that handles geodesic arcs on sphere and applied a small syntactical fix to the tracing traits.

📝 [Tetrahedral Mesh Generation](https://doc.cgal.org/5.5/Manual/packages.html#PkgMesh3)

• Added the function [`remove_isolated_vertices()`](https://doc.cgal.org/5.5/Mesh_3/classCGAL_1_1Mesh__complex__3__in__triangulation__3.html#ace57c4e777da457c6e33b4f6e89949ce) as a post-processing step for the tetrahedral mesh generation.

📝 [Polygon Mesh Processing](https://doc.cgal.org/5.5/Manual/packages.html#PkgPolygonMeshProcessing)

• Added the function [`CGAL::Polygon_mesh_processing::orient_triangle_soup_with_reference_triangle_soup()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__orientation__grp.html#ga855b1c55c201b91ab04eebd2811a87fd), which enables re-orienting the faces of a triangle soup based on the orientation of the nearest face in a reference triangle soup.
• Added the function [`CGAL::Polygon_mesh_processing::compatible_orientations()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__orientation__grp.html#ga9ac9b9434084b64f3304df636c3178a3), which enables to retrieve the (in)compatibility of orientations of faces from different connected components.
• Added the function [`CGAL::Polygon_mesh_processing::tangential_relaxation()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__meshing__grp.html#ga136c659162e5360354db5879db7431b4), which applies an area-based tangential mesh smoothing to the vertices of a surface triangle mesh.
• Added the named parameter `visitor` to the function [`triangulate_hole()`](https://doc.cgal.org/5.5/Polygon_mesh_processing/group__PMP__hole__filling__grp.html#gad2d3c43bce0ef90a16530478196d7f42), which enables to track progress with callbacks.
• Added more functions in the [visitor of the corefinement based methods](https://doc.cgal.org/5.5/Polygon_mesh_processing/classPMPCorefinementVisitor.html) to track progress.

📝 [Surface Mesh Simplification](https://doc.cgal.org/5.5/Manual/packages.html#PkgSurfaceMeshSimplification)

• Introduced four variations of the Garland-Heckbert simplification algorithm based on the probabilistic approach of Trettner and Kobbelt (Fast and Robust QEF Minimization using Probabilistic Quadrics): [`GarlandHeckbert_plane_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__plane__policies.html), [`GarlandHeckbert_probabilistic_plane_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__probabilistic__plane__policies.html), [`GarlandHeckbert_triangle_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__triangle__policies.html), and [`GarlandHeckbert_probabilistic_triangle_policies`](https://doc.cgal.org/5.5/Surface_mesh_simplification/classCGAL_1_1Surface__mesh__simplification_1_1GarlandHeckbert__probabilistic__triangle__policies.html).
• The class `GarlandHeckbert_policies` has been deprecated, `GarlandHeckbert_plane_policies` replaces it.

📝 [Point Set Processing](https://doc.cgal.org/5.5/Manual/packages.html#PkgPointSetProcessing3)

• A new optional named parameter, `min_points_per_cell` has been added to [`grid_simplify_point_set()`](https://doc.cgal.org/5.5/Point_set_processing_3/group__PkgPointSetProcessing3Algorithms.html#ga7757ef9b3900e42fde26f5a0ac56e20f). By adding a minimal number of points in a cell such that a point is retained, one can also filter out low density areas and outliers: in the case of densely sampled point clouds, this yields better results than using grid simplification and then outlier removal, while being very vast. The default value is `1` to keep the previous behavior as default.

📝 [dD Spatial Searching](https://doc.cgal.org/5.5/Manual/packages.html#PkgSpatialSearchingD)

• Added the member function [`write_graphviz()`](https://doc.cgal.org/5.5/Spatial_searching/classCGAL_1_1Kd__tree.html#ac2851b5cafb8d5cce0dc5fb107c8f13f) to the class `Kd_tree` that writes the tree in a stream in the [Graphviz](https://graphviz.org/) format.

📝 [CGAL and the Boost Graph Library (BGL)](https://doc.cgal.org/5.5/Manual/packages.html#PkgBGL)

• Added the function [`invert_selection()`](https://doc.cgal.org/5.5/BGL/structCGAL_1_1Face__filtered__graph.html#aa428541ebbdd35f9a6e9a3ffd60178df) in the class [`Face_filtered_graph`](https://doc.cgal.org/5.5/BGL/structCGAL_1_1Face__filtered__graph.html), which toggles the selected status of a graph: selected faces are deselected, and unselected faces are selected.