remove bodies after collision (bullet physics)

Question

I have a setup like this for collision detection:

struct ZombieBulletCallback : public btCollisionWorld::ContactResultCallback
  {
     ZombieBulletCallback(BulletStuff* ptr) : bullet(ptr) {}

     btScalar addSingleResult(btManifoldPoint& cp,
     const btCollisionObjectWrapper* colObj0Wrap,
     int partId0,
     int index0,
     const btCollisionObjectWrapper* colObj1Wrap,
     int partId1,
     int index1)
     {
        // your callback code here
        char strr[256];
        sprintf_s(strr, "zombie-bullet collision \n");
        OutputDebugString(strr);

        // increment points
        bullet->currentPoints += 10;

        // increase the kill counter
        bullet->killCounter += 1;

        // TODO remove bodies

        return 1.f;
     }

     BulletStuff* bullet;
  };

  ZombieBulletCallback zombieBulletCollision(this);

  for (int i = 0; i < zombies.size(); i++) {
     for (int j = 0; j < bullets.size(); j++) {
         bt_dynamicsWorld->contactPairTest(zombies[i], bullets[j], zombieBulletCollision);
     }
  }

I want to remove the bodies after the collision is detected.

The struct has access to colObj0Wrap and colObj1Wrap (type const btCollisionObjectWrapper*) which, I assume, are the 2 bodies that collide. I have tried this:

bullet->bt_dynamicsWorld->removeCollisionObject(colObj0Wrap->getCollisionObject());

but this gives an error: argument of type const btCollisionObject* is incompatible with param of type btCollisionObject*

How do I remove those 2 bodies from the world?

Answer 1

The difference that causes the incompatibility is the const qualifier of const btCollisionObject*.

I never tried to remove objects during collision or whatever dispatching and I doubt, that it will work flawlessly.

Since you're doing manual contact tests, you could try to remove the collision object using the const_cast operator: bullet->bt_dynamicsWorld->removeCollisionObject(const_cast<btCollisionObject*>(colObj0Wrap->getCollisionObject())); but again, enforcing that might not work properly now, or after changes to the simulation steps.

Instead, I would collect the 'dead' zombies via ContactResultCallback in another container defeatedZombies for deferred removal from bt_dynamicsWorld and zombies (at the end of a simulation step, or your nested loops, respectively).