internal override bool needsResponse( btCollisionObject body0, btCollisionObject body1 )
{
//here you can do filtering
bool hasResponse =
( body0.hasContactResponse() && body1.hasContactResponse() );
//no response between two static/kinematic bodies:
hasResponse = hasResponse &&
( ( !body0.isStaticOrKinematicObject() ) || ( !body1.isStaticOrKinematicObject() ) );
return hasResponse;
}