[SOLVED] Bullet physics randomly throws errors

Troubleshooting physics
1

Hello,
when I’m using jbullet, I have some random errors are appearing (even when a player is just walking). I have tried using different libraries from maven, such as:
cz.advel.jbullet : jbullet
com.github.stephengold : jbullet
com.github.stephengold : Libbulletjme
Now I’m using last, and I receive randomly these errors that can sometimes crash my program, or stop world generation thread:

java.lang.NullPointerException
        at com.bulletphysics.collision.dispatch.CollisionWorld$RayResultCallback.needsCollision(CollisionWorld.java:673)
        at com.bulletphysics.collision.dispatch.CollisionWorld.rayTest(CollisionWorld.java:555)
        at com.jme3.bullet.PhysicsSpace.rayTest(PhysicsSpace.java:781)
        at com.jme3.bullet.control.BetterCharacterControl.checkOnGround(BetterCharacterControl.java:503)
        at com.jme3.bullet.control.BetterCharacterControl.prePhysicsTick(BetterCharacterControl.java:199)
        at com.jme3.bullet.PhysicsSpace$3.internalTick(PhysicsSpace.java:318)
        ...


java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
        at com.jme3.bullet.BulletAppState.postRender(BulletAppState.java:386)
        at com.jme3.app.state.AppStateManager.postRender(AppStateManager.java:381)
        at com.jme3.app.SimpleApplication.update(SimpleApplication.java:274)
        ...

Exception in thread "Chunk" java.lang.NullPointerException
        at com.jme3.bullet.PhysicsSpace.addRigidBody(PhysicsSpace.java:617)
        at com.jme3.bullet.PhysicsSpace.addCollisionObject(PhysicsSpace.java:457)
        at com.jme3.bullet.control.RigidBodyControl.setPhysicsSpace(RigidBodyControl.java:394)
        at com.jme3.bullet.PhysicsSpace.add(PhysicsSpace.java:436)
        ...

Exception in thread "pool-8-thread-1" java.lang.ClassCastException: class com.bulletphysics.collision.shapes.CompoundShape cannot be cast to class com.bulletphysics.collision.shapes.ConvexShape (com.bulletphysics.collision.shapes.CompoundShape and com.bulletphysics.collision.shapes.ConvexShape are in unnamed module of loader 'app')
        at com.bulletphysics.collision.dispatch.ConvexConvexAlgorithm.processCollision(ConvexConvexAlgorithm.java:109)
        at com.bulletphysics.collision.dispatch.ConvexTriangleCallback.processTriangle(ConvexTriangleCallback.java:163)
        at com.bulletphysics.collision.shapes.BvhTriangleMeshShape$MyNodeOverlapCallback.processNode(BvhTriangleMeshShape.java:268)
        at com.bulletphysics.collision.shapes.OptimizedBvh.walkStacklessQuantizedTree(OptimizedBvh.java:955)
        at com.bulletphysics.collision.shapes.OptimizedBvh.reportAabbOverlappingNodex(OptimizedBvh.java:703)
        at com.bulletphysics.collision.shapes.BvhTriangleMeshShape.processAllTriangles(BvhTriangleMeshShape.java:163)
        at com.bulletphysics.collision.shapes.TriangleMeshShape.localGetSupportingVertex(TriangleMeshShape.java:71)
        at com.bulletphysics.collision.shapes.TriangleMeshShape.recalcLocalAabb(TriangleMeshShape.java:88)
        at com.bulletphysics.collision.shapes.BvhTriangleMeshShape.<init>(BvhTriangleMeshShape.java:84)
        at com.bulletphysics.collision.shapes.BvhTriangleMeshShape.<init>(BvhTriangleMeshShape.java:63)
        at com.jme3.bullet.collision.shapes.MeshCollisionShape.createShape(MeshCollisionShape.java:138)
        at com.jme3.bullet.collision.shapes.MeshCollisionShape.createCollisionMesh(MeshCollisionShape.java:89)
        at com.jme3.bullet.collision.shapes.MeshCollisionShape.<init>(MeshCollisionShape.java:77)
        at com.jme3.bullet.collision.shapes.MeshCollisionShape.<init>(MeshCollisionShape.java:67)
        at com.jme3.bullet.util.CollisionShapeFactory.createSingleMeshShape(CollisionShapeFactory.java:257)
        at com.jme3.bullet.util.CollisionShapeFactory.createCompoundShape(CollisionShapeFactory.java:123)
        at com.jme3.bullet.util.CollisionShapeFactory.createCompoundShape(CollisionShapeFactory.java:143)
        at com.jme3.bullet.util.CollisionShapeFactory.createMeshCompoundShape(CollisionShapeFactory.java:158)
        at com.jme3.bullet.util.CollisionShapeFactory.createMeshShape(CollisionShapeFactory.java:200)
        ...

Also, I’m using BulletAppState.ThreadingType.PARALLEL, and not BulletAppState.ThreadingType.SEQUENTIAL because then I receive even more errors.

The BetterCharacterControl has nothing any special:

playerNode.setLocalTranslation(new Vector3f(4, 5, 2));
player = new BetterCharacterControl(0.5f, 6f, 2f);
player.setJumpForce(new Vector3f(0f, 35f, 0f));
playerNode.addControl(player);
bulletAppState.getPhysicsSpace().add(player);
bulletAppState.getPhysicsSpace().addAll(playerNode);
rootNode.attachChild(playerNode);

And for moving player: player.setWalkDirection(walkDirection.multLocal(1))

Finally, for adding physics for terrain(chunks) I use:

CollisionShape shape = CollisionShapeFactory.createMeshShape(chunkSpat)
RigidBodyControl chunkPhys = new RigidBodyControl(shape, 0);
PhysicsSpace state = Storage.bulletAppState.getPhysicsSpace();
chunkSpat.addControl(chunkPhys);
Transformation.spawnObject(chunkSpat, node, app);
state.add(chunkPhys);

I really don’t know what to do.

2

Are you using JMonkeyEngine?

None of the libraries you’ve tried is intended for use with JMonkeyEngine. The physics libraries commonly used with JMonkeyEngine are: Minie, jme3-bullet, and jme3-bullet. Both jMonkeyEngine and Minie provide tutorials and sample apps you can use as a starting point.

If you won’t use JMonkeyEngine for some reason, then you’ve got a difficult climb ahead. Libbulletjme provides a couple single-threaded sample apps in its README file. Have you successfully run those apps?

3

it is outdated lib. use jme3-bullet / minie instead

4

I’m using these libraries with jme3-jbullet at the same time. Using only jme3-bullet(jbullet) also works, but in Hello Physics tutorial I’ve seen that there are both jme bullet and cz.advel.jbullet : jbullet, so I have experimented changing that second library.

5

Now I’ve tried using Minie, and none of that issues appears.

2 Likes
6

I guess it’s not very clear how all the different physics libraries fit together.

  • Minie is intended for use with JMonkeyEngine. It can’t be combined with any other physics library. It depends on jme3-core, jme3-terrain, Heart, and now SimMath, but those dependencies are handled automatically if you build using Maven or Gradle.

  • jme3-jbullet is part of JMonkeyEngine. It depends on jme3-core, jme3-terrain, jbullet, stack-alloc, and vecmath. In the past, you had to explicitly provide jbullet and stack-alloc. However, since JME 3.4, those dependencies are handled automatically if you build using Maven or Gradle.

  • jme3-bullet was removed from JMonkeyEngine effective with JME 3.4. It required either jme3-bullet-native (for desktops) or jme3-bullet-native-android (for Androids) or both.

  • Libbulletjme isn’t intended for use with JMonkeyEngine. Minie makes use of Libbulletjme’s native libraries, but that’s handled behind the scenes, so app developers never see the dependency.

Because jme3-bullet, jme3-jbullet, and Minie were (at one time) intended as drop-in replacements for one another, they provide many of the same APIs. If you combine them, you may encounter all manner of strange failures.

7

Since you mentioned, why does Minie depend on jme3-terrain? seems that it should be specific dependency for making terrains.

2 Likes
8

That’s a good question.

All JMonkeyEngine physics libraries depend on “jme3-terrain”, because CollisionShapeFactory uses TerrainPatch and TerrainQuad to generate collision shapes for terrain.

1 Like