Weird box interaction with default dynamics setup

[Mind Calamity]

Excuse the non-existent lighting and lack of detail, I'm using the default setup copy-pasted from the BasicDemo code, and adopted to my engine.

Here's the code, just in case:

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	///collision configuration contains default setup for memory, collision setup. Advanced users can create their own configuration.
	mColCfg = new btDefaultCollisionConfiguration();

	///use the default collision dispatcher. For parallel processing you can use a diffent dispatcher (see Extras/BulletMultiThreaded)
	mColDispatcher= new	btCollisionDispatcher(mColCfg);

	///btDbvtBroadphase is a good general purpose broadphase. You can also try out btAxis3Sweep.
	mBroadphase = new btDbvtBroadphase();

	///the default constraint solver. For parallel processing you can use a different solver (see Extras/BulletMultiThreaded)
	mConstraintSolver = new btSequentialImpulseConstraintSolver;

And then using those, I'm creating the world like so:

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		world = new btDiscreteDynamicsWorld
			( mPhysicsSys->getCollisionDispatcher()
			, mPhysicsSys->getBroadphaseInterface()
			, mPhysicsSys->getConstraintSolver()
			, mPhysicsSys->getCollisionConfig());

		world->setGravity(btVector3(0,-10,0));

Simulating it:

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world->stepSimulation(timeSinceLastUpdate, 5);

I'm using a simple motion state setup to synchronize my graphics objects with the physics objects, no problems there.

Here's my object creation:

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	btTransform bulletTrans;
	bulletTrans.setOrigin(toBullet(trans->getPosition()));
	bulletTrans.setRotation(toBullet(trans->getOrientation()));

	mMotionState = new MotionState(trans, bulletTrans);

	BoxParams params = dynamic_cast<BoxParams&>(geometryParams);
	mShape = new btBoxShape(toBullet(params.halfExtents)); // halfExtents is Vector3(1, 1, 1)
	
	btVector3 inertia(0,0,0);

	mShape->calculateLocalInertia(mass, inertia);

	btRigidBody::btRigidBodyConstructionInfo rbInfo(mass, mMotionState, mShape, inertia);
	rbInfo.m_restitution = 0.2f;
	rbInfo.m_friction = 1.5f;
	mBody = new btRigidBody(rbInfo);

Sorry for spamming code, and thanks in advance for any replies

[allsey87]

The problem is mostly likely in your implementation of btMotionState. Also show the code for the toBullet method and explain in detail what the 'weird' behaviour you are seeing is.

[Mind Calamity]

Here's the header of my motion state implementation:

Header: http://pastebin.com/NVcfNq2K
Source: http://pastebin.com/NgPuMVXh

I made a video for more detail: http://www.youtube.com/watch?v=eFareVg4XC8

My transform class is basically an Ogre SceneNode.

And my conversion functions:

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	inline btQuaternion toBullet(const Ogre::Quaternion &q)
	{
		return btQuaternion(q.x, q.y, q.z, q.w);
	}
	inline btVector3 toBullet(const Ogre::Vector3 &v)
	{
		return btVector3(v.x, v.y, v.z);
	}

	inline Ogre::Quaternion toOgre(const btQuaternion &q)
	{
		return Quaternion(q.w(), q.x(), q.y(), q.z());
	}

	inline Ogre::Vector3 toOgre(const btVector3 &v)
	{
		return Vector3(v.x(), v.y(), v.z());
	}

[Mind Calamity]

Weird, it seems that the btTransform that is passed to setWorldTransform of my motion state seems to always have an identity rotation - it's always at 1 0 0 0.

[Mind Calamity]

Thanks to xissburg (on the IRC) for pointing out that zero/infinite inertia can cause behavior like this. Apparently the problem was in a piece of code I removed while pasting here and calculateLocalInertia wasn't getting called at all.