Bulletphysics body goes through floor

Question

i have the following problem: I'd like to use bullet physics for moving the Character around. so far i have a severe problems with jumping: if i fall on the ground, the body (the Character) sinks into the ground for a couple miliseconds. the longer he falls, the more he sinks. Im using a gravity of 20, a cylindershape, and a groundplane with sleeping thresholds of 0,0. is there any way to fix this?

Answer 1

It sounds like your objects are moving too fast in each simulation step. The result of this could cause the two objects to over-penetrate. In the case of the character controller code provided there is a recoverFromPenetration that is called to move the object that caused the collision backwards (backwards being defined as calculated from the normals of the penetrating polygons) until it is no longer penetrating.

void btKinematicCharacterController::preStep (  btCollisionWorld* collisionWorld)
{

        int numPenetrationLoops = 0;
        m_touchingContact = false;
        while (recoverFromPenetration (collisionWorld))
        {
                numPenetrationLoops++;
                m_touchingContact = true;
                if (numPenetrationLoops > 4)
                {
                        //printf("character could not recover from penetration = %d\n", numPenetrationLoops);
                        break;
                }
        }

        m_currentPosition = m_ghostObject->getWorldTransform().getOrigin();
        m_targetPosition = m_currentPosition;
//      printf("m_targetPosition=%f,%f,%f\n",m_targetPosition[0],m_targetPosition[1],m_targetPosition[2]);


}

It tries to do this 4 times and if it does not resolve the penetration the recovery code fails and terminates with the objects still penetrating one another. This controller code is not intended to be production code but rather a starting point and framework for further customization and development. It serves its purpose pretty well but as you have discovered there are limitations.