How do I properly 'link' GhostObject to (moving) RigidBody?

[BLK Dragon]

Just updating GhostObject transform after RigidBody is not enough -- if RigidBody is moving fast enough (15-20 units per second or so), the GhostObject can easily "miss" collision with world (tri-mesh CollisionObject).

It seems that I need 'hard'-constraint GhostObject to RigidBody, but constraints are only working with RigidBodies, not CollisionObjects.

Any suggestions?

[trollington]

Show us your code -- are you using convexSweepTest?

[BLK Dragon]

Show us your code -- are you using convexSweepTest?

No, I don't use convexSweepTest.
Collisions for phantoms are checked like this:

Code: Select all

    static btManifoldArray  manifold;
    btBroadphasePairArray&  pair        = (static_cast<btPairCachingGhostObject*>(_obj))->getOverlappingPairCache()->getOverlappingPairArray();
    int                     pair_cnt    = pair.size();
    btOverlappingPairCache* pair_cache  = PhysWorld::Instance()->dynamics_world()->getPairCache();
    bool                    do_clear    = pair_cnt == 0;

    for( int i=0; i!=pair_cnt; ++i )
    {
        manifold.clear();

        btBroadphasePair*   cd_pair = pair_cache->findPair( pair[i].m_pProxy0, pair[i].m_pProxy1 );

        if( cd_pair )
        {
            if( cd_pair->m_algorithm )
                cd_pair->m_algorithm->getAllContactManifolds( manifold );

            for( int m=0; m<manifold.size(); ++m )
            {
                 // get contact-points etc.
            }
        }
    }

[Erwin Coumans]

For fast moving objects it is best to use the convexSweepTest.

The btGhostObject has some way to perform such sweep test too. You can check the implementation in Bullet/src/BulletDynamics/Character/btKinematicCharacterController:

Code: Select all

 if (m_useGhostObjectSweepTest)
                {
                        m_ghostObject->convexSweepTest (m_convexShape, start, end, callback, collisionWorld->getDispatchInfo().m_allowedCcdPenetration);
                } else
                {
                        collisionWorld->convexSweepTest (m_convexShape, start, end, callback, collisionWorld->getDispatchInfo().m_allowedCcdPenetration);
                }

[BLK Dragon]

For fast moving objects it is best to use the convexSweepTest.

Yes, now I understand that, thanks for clarification.

There's one thing about btCollisionWorld::ConvexResultCallback that I don't quite understand:
what happens when there're multiple points of contact between ghost-object and some other collision-object -- do I get all of them, first one?

UPD:
Actually, all the contact points (if there're multiple contacts) are passed to btCollisionWorld::ConvexResultCallback::addSingleResult(),
so it's all works fine.