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Adding bullet collisions

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mixmaster

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Bullet Collision


After reading the bullet manual, I only figured out I needed to add a callback at the Tick level. The problem with callbacks and C++ is they dont mix well. Anyway I added a static function to my main Bullet class which holds the Dynamics World, called lsTickCallback. Then I added the following to my constructor.


dynamicsWorld = new btDiscreteDynamicsWorld( dispatcher, axis_sweep3, solver, collisionConfiguration );
dynamicsWorld->setGravity(btVector3(0,-10,0));

// NEW set callback
dynamicsWorld->setInternalTickCallback( &lsTickCallback, static_cast<void *>(this) );




Here is the full static function.


void lsBulletWorld::lsTickCallback( btDynamicsWorld *world, btScalar timeStep )
{
lsBulletWorld *w = static_cast(world->getWorldUserInfo());
w->lsProcessCallback( timeStep );
}




As you can see I pull the real class instance I need to call from the User defined pointer I set in the first listing. Once I have the pointer I call my function.

Now I just need to read in all the hit pairs from the cashe. Not to hard. Here's my full debug function.


void lsBulletWorld::lsProcessCallback( btScalar timeStep )
{
// local instance callback
cout << scene->getName() << " : bullet world just ticked by " << timeStep << " seconds" << endl;

lsNode* obj_A;
lsNode* obj_B;

// get hits
int numManifolds = dynamicsWorld->getDispatcher()->getNumManifolds();
for (int i=0;i {
btPersistentManifold* contactManifold = dynamicsWorld->getDispatcher()->getManifoldByIndexInternal(i);
btCollisionObject* obA = static_cast(contactManifold->getBody0());
btCollisionObject* obB = static_cast(contactManifold->getBody1());

// Scene nodes
obj_A = (lsNode*)obA->getUserPointer();
obj_B = (lsNode*)obB->getUserPointer();
if( obj_A )
cout << "Node A : " << obj_A->getName() << endl;
if( obj_B )
cout << "Node B : " << obj_B->getName() << endl;

int numContacts = contactManifold->getNumContacts();
for (int j=0;j {
btManifoldPoint& pt = contactManifold->getContactPoint(j);
if (pt.getDistance()<0.f)
{
const btVector3& ptA = pt.getPositionWorldOnA();
const btVector3& ptB = pt.getPositionWorldOnB();
const btVector3& normalOnB = pt.m_normalWorldOnB;

cout << "Hit B: " << ptB.getX();
cout << ", " << ptB.getY();
cout << ", " << ptB.getZ();
cout << endl;

cout << "Normal B: " << normalOnB.getX();
cout << ", " << normalOnB.getY();
cout << ", " << normalOnB.getZ();
cout << endl;

}
}
}

}




I should explain how I set the UserPointer that I get from obj_A = (lsNode*)obA->getUserPointer();. When any bullet object is set to a lsNode in my scenes I automaticlly set the UserPointer to that node. So now its just an easy operation to tell the nodes what happened. Just keep in mind if your scene objects are deleted, you may not be able to access them. Call in the right order.
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