ode4j

ode4j is a Java port of ODE.

ODE is an open source, high performance library for simulating rigid body dynamics. It is fully featured, stable, mature and platform independent with an easy to use C/C++ API. It has advanced joint types and integrated collision detection with friction. ODE is useful for simulating vehicles, objects in virtual reality environments and virtual creatures.

The latest released version of ode4j is 0.5.2, but the master branch may contain fixes and improvements. Release 0.5.0 contains all changes up to ODE 0.16.3.

Resources

• ode4j contains numerous custom features that are not present in ODE (see also Wiki).

• The ODE forum is useful for questions around physics and general API usage:

• There is a new Discord channel around ode4j/Java.

• The ode4j forum is for problems and functionality specific to ode4j/Java.

• There is also the old website, including some screenshots.

There is also a GWT compatible fork of ode4j.

The following artifact contains the complete physics engine (examples etc. are not included):

<dependency>
    <groupId>org.ode4j</groupId>
    <artifactId>core</artifactId>
    <version>0.5.2</version>
</dependency>

News

2023-10-07: Release 0.5.2:

• Bug fix for DVector3.cross() + some minor improvements

2023-09-17: Release 0.5.1:

• Bug fix for demos running on Apple Silicon/Retina

2023-05-27: Release 0.5.0. Full update to ODE 0.16.3 + Java 8 as baseline:

• Port of all changes up to ODE 0.16.3
• Java 8 required
• LWJGL 3.x for demos
• Tested Android compatibility with API level 24 (Android 7 / Nougat)
• CI for Java 8 + 9
• Improved API (mostly in math package)
• Cleanup (e.g. full JUnit 4 style test, fixed most lint warnings up to Java 17)
• Bug fixes
• BREAKING CHANGE: DSpace.getGeoms() now returns DGeom instead of DxGeom.

2023-03-31: Release 0.4.1 & 0.4.2. Mostly a bugfix release + some API helper methods:

• Fix OSGI bundle info to require Java 1.7 instead of 7.0
• New helper methods: `
  • DBody : addLinearVelocity()
  • DVector3: reAdd(), eqToRadians(), eqToDegrees() (convert angles in a DVector3, eq prefix means that the object is set equal to the result)
  • DQuaternion: ZERO, IDENTITY, isEq(), length(), lengthSquared(), toEuler(), fromEuler(), toEulerDegrees(), fromEulerDegrees(), eqInverse(), reInverse().
• 0.4.2 fixes some small regressions with 0.4.1

2019-01-03: Release 0.4.0. This release contains most of the changes that happened between ODE 0.13.1 and ODE 0.16.0, plus some original features:

• Java 9 / modularization (generated jar files are Java 7) (io7m)
• Implemented/migrated multi-threading for the stepper (Pjotr)
• SAP-Space optimization: Avoid collision detection for immobile bodies (Pjotr)
• New BVH tree for better scalability with 10'000 bodies or more, ported from the Turbulenz Engine (Pjotr)
• Fixed javadoc to compile without warnings

2018-03-26: Snapshot release 0.4.0

• Java 9 / modularization (generated jar files are Java 7) (io7m)

2017-11-16: Snapshot release 0.4.0

• Java 7 and updated dependencies
• Implemented/migrated multi-threading for the stepper (Pjotr)
• SAP-Space optimization: Avoid collision detection for immobile bodies (Pjotr)
• New BVH tree for better scalability with 10'000 bodies or more, ported from the Turbulenz Engine (Pjotr)

2017-10-06: Release of ode4j 0.3.1

• Numerous bugfixes and improvement, see CHANGELOG
• This is the last release built with Java 6.

Project overview

• The "core" package contains the main library code. The public API is in:

  • org.ode4j.math
  • org.ode4j.ode
  • org.ode4j.ode.ragdoll

  All other packages are "internal" and should normally not be used.

• The "demo" package contains demo application for various simulation problems. The package contains the "drawstuff" library which is handy for visualizing simple physics simulation but should not be used for real applications (it is slow and clunky). Please use proper library such as lwjgl for your own games or simulations.

• The "core-cpp" and "demo-cpp" packages are legacy packages and should be ignored.

General recommendations

• Please use DWorld.quickStep(...) instead of DWorld.step(). The latter is slower and appears to be less stable.
• Consider disabling geometries that do not move. For an example, refer to DemoCrash. The demo disables boxes that have not moved for a few steps. If a whole "island" of bodies is disabled, it is automatically excluded from simulation (bodies are automatically re-enabled when necessary), see also ODE wiki.
• Set OdeConfig.dDEBUG = true for debugging and = false for best performance.
• When compiling with JDK 9 or later, mvn will automatically use theon-jdk-9-plus profile and create modules.
• In case of GC problems (e.g. on Android): There may be excessive garbage collection due to frequent allocation of DContact objects. To avoid this, these objects can be nullified and reused. See PerfCards.nearCallback() for an example.

ODE vs od4j

While ode4j is a pretty literal port from ODE, there are some considerable differences (besides one being Java and the other being C++). Some differences concern the API, others are mostly internal.

ode4j supported ODE features

• ode4j ist mostly similar to ODE when compiling ODE with ./configure --enable-double-precision --with-trimesh=gimpact --enable-libccd. That means:
  • ode4j uses double precision throughout
  • ode4j supports only GIMPACT trimeshes, OPCODE is not supported
  • ode4j always uses libccd for collisions
• ode4j has multithreading support (ODE's "island" solver), however, ode4j does not support ODE's cooperative solver.
• ode4j has no special memory management (ODE has a "memory arena" concept).

Additional features in ode4j

ode4j contains some custom features that are not present in ODE (see also Wiki):

• DRagdoll & DConstrainedBallJoint, see DemoRagdoll and DemoJointConstrainedBall.
• DTrimeshHeightfield with support for holes. See DemoTrimeshHeightfield.
• Improved SAP space (SapSpace2) implementation that allows labelling bodies as "immobile", see SpacePerformanceTest.
• BVH space based on a bounding volume hierarchy index, see SpacePerformanceTest.
• Java multi-threading support, see DemoMultithreading.

ode4j API vs ODE API

ode4j's API is very similar to ODE's API, so most tutorials / demos should be easily translatable. However, there are some notable differences:

• Almost all objects in ode4j are created via the OdeHelper class.

• Math functions are located in ode4j.math and OdeMath. ode4j has different versions for some math objects, e.g. DVector3 and DVector3C where the trailing C indicates an immutable or Const version of the object.

• Class names in ode4j start with D instead of d in ODE. d...ID classes have been removed, use d... instead, e.g. dBodyID becomes DBody.

• ODE uses almost exclusively static methods. ode4j uses instead methods on objects where possible and methods have been renamed accordingly and their signature changed. Some examples:

  • dGeomSetRotation(geom, ...) becomes geom.setRotation(...)
  • dJointSetHingeAxis(hingeJoint, ...) becomes hingeJoint.setAxis(...)

  Many ODE methods have a skip parameter, this has been removed in ode4j.

• dCollide becomes OdeHelper.collide() and takes as argument a DContactGeomBuffer. This can be created via:

  DContactBuffer contacts = new DContactBuffer(MAX_CONTACTS); 
  OdeHelper.collide (o1, o2, MAX_CONTACTS, contacts.getGeomBuffer());
  

• Many classes have a "DESTRUCTOR" that replicates some C++ features, however this can usually be ignored.

ode4j internal differences

• ode4j's DLCP uses ROWPTRS = false
• SAP-Space uses different merge-sort instead of radix-sort
• ...

Version overview

ode4j versions and corresponding ODE versions:

• ode4j 0.5.0 contains all changes up to ODE 0.16.3.
• ode4j 0.4.0 contains most changes between 0.13.1 and 0.16.0.
• ode4j 0.3.1 is a port of ODE 0.13.1.
• ode4j 0.2.4 up to 0.2.9 are ports of ODE 0.12.1

Legal

ode4j: Copyright (c) 2009-2023 Tilmann Zäschke <ode4j(AT)gmx.de>. All rights reserved.

Like the original ODE, ode4j is licensed under LGPL v2.1 and BSD 3-clause. Choose whichever license suits your needs.

ode4j contains Java ports of the following software

• ODE/OpenDE: Copyright (c) 2001,2002 Russell L. Smith All rights reserved.

• GIMPACT (part of ODE/OpenDE): Copyright of GIMPACT (c) 2006 Francisco Leon. C.C. 80087371. email: projectileman(AT)yahoo.com

• LIBCCD: Copyright (c) 2010 Daniel Fiser <danfis(AT)danfis.cz>; 3-clause BSD License

• Turbulenz Engine: Copyright (c) 2009-2014 Turbulenz Limited; MIT License

ode4j uses the following libraries

• lwjglmaven

• JUnit 4

• slf4j

Contact

Tilmann Zaeschke ode4j (AT) gmx.de

Special thanks to contributors

Please let me know if I missed anyone!

• valb3r
• io7m
• ppiastucki(piotr) <-- Shoutout for major contributions!
• fommil
• peterkir
• neduard
• Namek