Bullet Physics Simplest Collision Example

Question

I\'m trying to use Bullet Physics for collision detection only. I don\'t need it to move any objects for me or handle rendering with callbacks. I just want to update object loca

Answer 1

You can check the contact information as explained here:

Contact Information

The best way to determine if collisions happened between existing objects in the world, is to iterate over all contact manifolds. This should be done during a simulation tick (substep) callback, because contacts might be added and removed during several substeps of a single stepSimulation call. A contact manifold is a cache that contains all contact points between pairs of collision objects. A good way is to iterate over all pairs of objects in the entire collision/dynamics world:

//Assume world->stepSimulation or world->performDiscreteCollisionDetection has been called

    int numManifolds = world->getDispatcher()->getNumManifolds();
    for (int i=0;igetDispatcher()->getManifoldByIndexInternal(i);
        btCollisionObject* obA = static_cast(contactManifold->getBody0());
        btCollisionObject* obB = static_cast(contactManifold->getBody1());

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

You may be interested in btGhostObject that keeps track of its own overlapping pairs.