Getting user data into InternalTickCallback

[Wavesonics]

I need to get a pointer to my physics manager in Bullet's TickCallback,

Any ideas on the best way to do this?

[Wavesonics]

Right now this is how I'm trying to do it:

1) Get collision object array from dynamics world (since that is passed to the callback)
(It's my understanding that all objects are CollisionObjects, thus getting the CollisionObjectArray from the dynamics world should include all the objects in the Dynamics world, is that right?)

2) Get the first object from the array, and grab it's stored user pointer, this should be my data that I set when creating the physics objects right?

3) Go to town with my new shinny user data

But this doesn't work. The user data doesn't seem to be correct.
Any other ideas?

[chunky]

http://chunkyks.com/world_userdata.diff ?

In fact, thinking about it, I'd like to put that forward as a request to be added to the main codebase, if there isn't already something obviously similar that I'm missing...

Gary (-;

[Wavesonics]

I was trying to not modify the source for upgradability, but i suppose this is the only way.

Ya, this really really needs to be patched in, are you going to submit it for 2.70?

[chunky]

are you going to submit it for 2.70?

I think I just did?

Gary (-;

[Wavesonics]

hehe ok, I thought you could actually submit it as a patch to the google code project or something like source forge

[Wavesonics]

Should we modify the patch to nitialize the userPointer to NULL in the dynamics world constructor?

[chunky]

http://chunkyks.com/world_userdata.diff
Updated

EDIT: I also noticed that btDynamicsWorld is actually derived from btCollisionWorld, so it may make more sense to put this userpointer in there... That's a question someone smarter than me would have to answer though

Gary (-;

[Wavesonics]

Ya Chunky I think your right, mostly since the userPointer is in CollisionObject and not RigidBody, so it would be in keeping with the current SOP

[Sly]

Why hack the code? Derive your own world class with the info you want.

Code: Select all

class MyPhysicsWorld : public btDiscreteDynamicsWorld
{
public:
	MyPhysicsWorld(MyPhysicsManager *manager, btDispatcher* dispatcher,btBroadphaseInterface* pairCache,btConstraintSolver* constraintSolver,btCollisionConfiguration* collisionConfiguration)
    : btDiscreteDynamicsWorld(dispatcher, pairCache, constraintSolver, collisionConfiguration)
  {
    m_manager = manager;
  }

  static void InternalTickCallback(const btDynamicsWorld *world, btScalar timeStep)
  {
    MyPhysicsWorld *myWorld = (MyPhysicsWorld *)world;
    // Do something with myWorld->m_manager
  }

  MyPhysicsManager *m_manager;
};

    manager = new MyPhysicsManager;
    world = new MyPhysicsWorld(manager, collisionDispatcher, broadphaseInterface, constraintSolver, collisionConfig);
    world->setInternalTickCallback(MyPhysicsWorld::InternalTickCallback);

[Wavesonics]

It's not hacking, this is how Open Source projects get better.

This is something that nearly anyone using the tick callback would need, so it's providing a necessary improvement to the Open Source project.

[chunky]

Technically the callback was only added in the last version or two, so the project still lacking other stuff that's central and useful to callbacks is hardly a surprise

Gary (-;

[Erwin Coumans]

If you have useful patches, please make sure to submit it to the Googlecode issue tracker, so it will get the right attention.

This one already got into the latest SVN:

Code: Select all

	/// Set the callback for when an internal tick (simulation substep) happens, optional user info
		void setInternalTickCallback(btInternalTickCallback cb,	void* worldUserInfo=0) 
		{ 
			m_internalTickCallback = cb; 
			m_worldUserInfo = worldUserInfo;
		}

		void	setWorldUserInfo(void* worldUserInfo)
		{
			m_worldUserInfo = worldUserInfo;
		}

		void*	getWorldUserInfo() const
		{
			return m_worldUserInfo;
		}

Thanks a lot,
Erwin

[Wavesonics]

awesome, great to hear. Just out of curosity, was this implemented in Collision world or dynamics world?