Ghost objects - bulletphysics

Question

I am trying to implement a simple ghost object in bulletphysics, this is how I create ghost objects:

btGhostPairCallback* ghostCall = new btGhostPairCallback();
world->getBroadphase()->getOverlappingPairCache()->setInternalGhostPairCallback(ghostCall);

btGhostObject* ghostObj = new btGhostObject();
btCollisionShape* shape = new btBoxShape(btVector3(ofGetWidth()+1000, ofGetHeight()+1000, 50));
ghostObj->setCollisionShape(shape);
btTransform trans;
trans.setIdentity();
trans.setOrigin(btVector3(0,0,-500));
ghostObj->setWorldTransform(trans);
ghostObj->setCollisionFlags( btCollisionObject::CF_NO_CONTACT_RESPONSE);
world->addCollisionObject(ghostObj,btBroadphaseProxy::SensorTrigger,btBroadphaseProxy::AllFilter & ~btBroadphaseProxy::SensorTrigger);

and here's how to try to find a collision:

btCollisionObject* obj = world->getCollisionObjectArray()[j];
btRigidBody* body = btRigidBody::upcast(obj);

    btAlignedObjectArray < btCollisionObject* > objsInsidePairCachingGhostObject;
    btAlignedObjectArray < btCollisionObject* >* pObjsInsideGhostObject = NULL;
    btGhostObject* ghost = btGhostObject::upcast(obj);

    if(ghost){
        objsInsidePairCachingGhostObject.resize(0);
        pObjsInsideGhostObject = &ghost->getOverlappingPairs();
        cout << ghost->getNumOverlappingObjects() << endl;

but I always get the answer that all my objects in the world are in conflict with the ghost object.

Can anyone help me get a functional simple ghost object?

thank

Answer 1

From what I understand a little from GhostObject, you override its default collision flags. Try changing this line.

ghostObj->setCollisionFlags( btCollisionObject::CF_NO_CONTACT_RESPONSE);

at

ghostObj->setCollisionFlags( ghostObj->getCollisionFlags() | btCollisionObject::CF_NO_CONTACT_RESPONSE);

NTN

Answer 2

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