Collision Feedback question

[sandeep_slash]

When I collide a CompoundShape with some other Objects, I want to know which childShape is colliding...

Can someone tell me how to do this?

[rusty]

I think you can do this with a custom back function in the narrow phase. The collision object changes the m_collisionShape member in btCollisionShape when it calls the near collision callback function to the current chape in the compound (with m_rootCollisionShape pointing to the compound shape).

So you can access the current shape by just calling getCollisionShape() from the collision object. The code would like something like this;

Code: Select all

void 
CustomNearCallback(
	btBroadphasePair& collisionPair, 
	btCollisionDispatcher& dispatcher, 
	const btDispatcherInfo& dispatchInfo)
{
	btCollisionObject* lpObj1 = NULL;
	btCollisionObject* lpObj2 = NULL;

	if (collisionPair.m_pProxy0)
		lpObj1 = static_cast<btCollisionObject*>(collisionPair.m_pProxy0->m_clientObject);

	if (collisionPair.m_pProxy1)
		lpObj2 = static_cast<btCollisionObject*>(collisionPair.m_pProxy1->m_clientObject);

	if ((NULL == lpObj1) || (NULL == lpObj2))
	{
		btCollisionDispatcher::defaultNearCallback(collisionPair, dispatcher, dispatchInfo);
		return;
	}

	btCollisionShape* lpShape1 = lpObj1->getCollisionShape();
	btCollisionShape* lpShape2 = lpObj2->getCollisionShape();

	/* Do you processing based on the actual shape here */

	btCollisionDispatcher::defaultNearCallback(collisionPair, dispatcher, dispatchInfo);
}

I hope that this helps!