anchor.diff:       (%body-ptr body) pos3 norm3)
       (values (ptr->v3 pos3) (ptr->v3 norm3))))
   
  -(defun material-pair-contact-position (material-pair body)
  +(defn material-pair-contact-position ((material-pair material-pair)
  +                                      (body body))
  +    (simple-array single-float (3))
     (declare (optimize (speed 3) (safety 1) (debug 1)))
     (with-foreign-objects ((pos3 :float 3)
                            (norm3 :float 3))
  
positive.code:      (%body-ptr body) pos3 norm3)
      (ptr->v3 pos3)))
  
  (defun material-pair-contact-normal (material-pair body)
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (with-foreign-objects ((pos3 :float 3)
                           (norm3 :float 3))
  
negative.code:      p3))
    pos3)
  
  (defn (setf material-pair-contact-normal)
      ((vec3 (simple-array single-float (3)))
       (material-pair material-pair))
      (simple-array single-float (3))
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (with-foreign-array (n3 vec3 '(:array :float 3))
      (newtonmaterialsetcontactnormaldirection
  