public override void DetectCollisions(IPhysicObject po, System.Collections.Generic.List <IPhysicObject> resp)
{
BulletPhysicObject BulletPhysicObject = po as BulletPhysicObject;
contactcallbac.objs = new List <IPhysicObject>();
world.ContactTest(BulletPhysicObject.Body, contactcallbac);
resp = contactcallbac.objs;
}