GitPedia

Minie

Integrate Bullet Physics and V-HACD into jMonkeyEngine projects (code has New BSD license)

From stephengold·Updated June 20, 2026·View on GitHub·

The [Minie Project][project] is about improving the integration of [Bullet real-time physics simulation][bullet] and [Khaled Mamou's V-HACD Library][vhacd] into [the jMonkeyEngine (JME) game engine][jme]. The project is written primarily in Java, distributed under the Other license, first published in 2018. Key topics include: bullet-physics, collision-detection, collision-shape, game-physics, inverse-kinematics.

Latest release: 9.0.3
December 20, 2025View Changelog →
<img height="150" src="https://i.imgur.com/YEPFEcx.png" alt="Minie Project logo">

The Minie Project is about improving the integration of
Bullet real-time physics simulation
and Khaled Mamou's V-HACD Library into
the jMonkeyEngine (JME) game engine.

It contains 6 subprojects:

  1. MinieLibrary: the Minie runtime library and its automated tests
  2. TutorialApps: tutorial apps
  3. MinieExamples: demos, examples, and non-automated test software
  4. MinieAssets: generate assets used in MinieExamples
  5. MinieDump: a command-line utility to dump J3O assets
  6. Jme3Examples: physics examples from jme3-examples

The DacWizard application, formerly a subproject,
is now a separate project at GitHub.

The VhacdTuner application, formerly a subproject,
is now a separate project at GitHub.

Complete source code (in Java) is provided under
a 3-clause BSD license.

<a name="toc"></a>

Contents of this document

<a name="why"></a>

Why use Minie?

jMonkeyEngine comes with jme3-jbullet,
its own Bullet integration library.
Why use Minie instead of jme3-jbullet?

  • Minie has many more features. (See the feature list below.)
  • Minie fixes many bugs found in jme3-jbullet.
  • Due to its shorter release cycle, future features and bug fixes
    will probably appear first in Minie.
  • Minie uses automated testing to reduce the risk of regressions and new bugs.
  • Minie's classes are better encapsulated, with fewer public/protected fields
    and less aliasing of small objects like vectors. This reduces the risk
    of accidentally corrupting its internal data structures.
  • Minie validates method arguments. This helps detect usage errors that
    can lead to subtle bugs.
  • Minie's source code is more readable and better documented.

Summary of added features:

  • Extensions to DynamicAnimControl
  • Soft-body simulation based on btSoftBody and btSoftRigidDynamicsWorld,
    including anchors and soft-body joints
  • Multi-body simulation based on btMultiBody and btMultiBodyDynamicsWorld
  • Convex decomposition of meshes using Khaled Mamou's V-HACD Library,
    including progress listeners
  • New6Dof physics joints based on btGeneric6DofSpring2Constraint
  • Alternative contact-and-constraint solvers based on btDantzigSolver,
    btLemkeSolver, btSolveProjectedGaussSeidel, and btNNCGConstraintSolver
  • collision shapes:
    • MultiSphere shapes based on btMultiSphereShape
    • Box2dShape shapes based on btBox2dShape
    • Convex2dShape shapes based on btConvex2dShape
    • EmptyShape shape based on btEmptyShape
  • debugging aids:
    • dump the contents of a BulletAppState, PhysicsSpace,
      CollisionShape, or MultiBody
    • visualize physics objects in multiple viewports
    • customize debug material per collision object
    • visualize the local axes, velocities, bounding boxes, CCD swept spheres,
      and gravity vectors of collision objects
    • visualize the children of compound collision shapes
    • optional high-resolution debug meshes for convex shapes
    • options to generate debug meshes that include indices,
      normals (for shading), and/or texture coordinates (for texturing)
  • all joints, shapes, collision objects, and multibodies
    implement the JmeCloneable and Comparable interfaces
  • enable/disable a PhysicsJoint
  • single-ended physics joints
  • ignore lists for collision objects
  • application-specific data for collision objects
  • access more parameters of rigid bodies, vehicles, characters, joints,
    collision shapes, contact/constraint solvers, etcetera
  • option to apply scaling with a RigidBodyControl

Some jme3-jbullet classes that Minie omits:

  • KinematicRagdollControl, HumanoidRagdollPreset, and RagdollPreset:
    use DynamicAnimControl instead
  • RagdollUtils: not needed

Other important differences:

  • PhysicsSpace.addAll() and PhysicsSpace.removeAll() add/remove collision
    objects only; they do not add/remove joints.
  • RagdollCollisionListener interface changed and moved
    from the com.jme3.bullet.collision package
    to the com.jme3.bullet.animation package.

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<a name="downloads"></a>

Downloads

Newer releases (since v0.5.0) can be downloaded from
GitHub.

Older releases (v0.1.1 through v0.4.5) can be downloaded from
the Jme3-utilities Project.

Maven artifacts since v3.1.0 are available from
MavenCentral.

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<a name="conventions"></a>

Conventions

Package names begin with jme3utilities.
(if Stephen Gold holds the copyright) or
com.jme3./jme3test. (if the jMonkeyEngine Project holds the copyright).

The source code and pre-built libraries are compatible with JDK 8.

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<a name="overview"></a>

Overview and design considerations

The role of physics simulation in games

Most computer games don't require detailed physics simulation.

  • Canned animations usually suffice to illustrate characters walking,
    jumping, and fighting.
  • Detecting when a character enters a fixed zone
    or comes into range of another character is a simple geometric calculation,
    provided the zone or range has a box or sphere shape.
  • For outer-space games, the equations of motion (Newton's 3rd Law) are easily
    implemented from scratch.

Other games require physics simulation, either because detailed physics is
integral to gameplay (as in bowling or auto racing) or else to enhance the
verisimilitude of effects such as collapsing buildings and/or people.
For such games, a real-time physics library such as Minie should prove useful.

How Minie works

How Minie works

Computational efficiency

The computational cost of collision detection grows rapidly with
the number of collision objects and the complexity of their shapes.
To simulate physics in real time, with modest CPUs,
it's vital to keep the physics simple:

  • Use very simple collision shapes (such as boxes, capsules, and spheres)
    wherever possible.
  • Minimize the number of collision objects by
    merging static bodies together and
    simulating only the most relevant moving bodies.
  • Minimize the number of nodes in each soft body.

Scaling the world

For a physics simulation, it might seem natural to choose kilograms and meters
as the units of mass and distance, respectively.
However, this is not a requirement, and for many games,
MKS units are not the best choice.

Bullet documentation recommends that dynamic bodies have
masses as close as possible to 1.

Also, to improve the performance and reliability of collision detection,
Bullet applies a margin to most collision objects.
By default, this margin is 0.04 physics-space units (psu).
While the margin is configurable, Bullet documentation
recommends against doing so.
For some collision shapes, margin increases the effective size of the object
and distorts its effective shape.
For this reason, it's undesirable to have a collision object
with any radius smaller than about 0.2 psu.

Dynamic bodies in forced contact tend to jiggle.
Jiggling is mostly noticeable for sharp-edged bodies (such as boxes)
resting on uneven surfaces, under high gravity.
The higher the gravity (in psu per second squared),
the shorter the time step (in seconds) needs to be.
For efficient and realistic simulation of Earth-like gravity (9.8 m/s^2)
with the default margin (0.04 psu) and time step (0.0167 seconds),
the psu should be 0.3 meters or larger.
This puts a soft lower limit on the dimensions (in psu) of dynamic bodies.

Since Minie's debug visualization assumes that physics coordinates are
equivalent to world coordinates, these recommendations could impact
model creation and scene-graph design.
Physics units should therefore be chosen with care,
preferably early in the development process.

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<a name="build"></a>

How to build Minie from source

How to build Minie from source

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<a name="tutorials"></a>
<a name="add"></a>
<a name="rigidbody"></a>
<a name="shape"></a>
<a name="debugging"></a>
<a name="new6dof"></a>
<a name="dac"></a>
<a name="detect"></a>
<a name="softbody"></a>

Tutorials

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<a name="demos"></a>

An overview of the demo applications

An overview of the demo applications

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<a name="links"></a>

YouTube videos about Minie:

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<a name="history"></a>

History

The evolution of this project is chronicled in
its release log.

Most of Minie was originally forked from jme3-bullet,
a library in the jMonkeyEngine Game Engine.

From January to November 2018, Minie was a subproject of
the Jme3-utilities Project.

Since November 2018, Minie has been a separate project, hosted at
GitHub.

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<a name="acks"></a>

Acknowledgments

Like most projects, the Minie Project builds on the work of many who
have gone before. I therefore acknowledge the following
artists and software developers:

  • Normen Hansen (aka "normen") for creating most of the jme3-bullet library
    (on which Minie is based) and also for helpful insights
  • Rémy Bouquet (aka "nehon") for co-creating
    KinematicRagdollControl (on which DynamicAnimControl is based),
    for creating the Jaime model, and also for many helpful insights
  • Jules (aka "dokthar") for creating the soft-body fork of jMonkeyEngine
    from which Minie's soft-body support is derived
  • Khaled Mamou for creating and licensing the V-HACD Library
    for decomposing meshes into convex hulls
  • Riccardo Balbo (aka "riccardo") for creating and licensing
    the V-HACD Java Bindings Project
  • "ndebruyn" for early testing of Minie on Android platforms
  • Pavly Gerges (aka "Pavl_G") for testing Minie on Raspberry Pi
  • Adam T. Ryder (aka "tryder") for creating and licensing
    the jME-TTF rendering system
  • [Paul Speed (aka "pspeed42")][pspeed], for creating the SimMath library
  • "oxplay2", for reporting a PhysicsRigidBody bug and helping me pin it down
  • "duncanj", for pull request #15
  • "qwq", for suggesting changes to how rigid-body contacts are managed
    and for authoring the ConveyorDemo application
  • Nathan Vegdahl, for creating the Puppet model
  • Tobias Jung, for distributing ProFont
  • plus the creators of (and contributors to) the following software:

I am grateful to GitHub, Sonatype, JFrog,
Travis, MacStadium, YouTube, and Imgur
for providing free hosting for this project
and many other open-source projects.

I'm also grateful to my dear Holly, for keeping me sane.

If I've misattributed anything or left anyone out, please let me know, so I can
correct the situation: sgold@sonic.net

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This article is auto-generated from stephengold/Minie via the GitHub API.Last fetched: 6/25/2026