anchor.diff:       (%body-ptr body) pos3 norm3)
       (ptr->v3 pos3)))
   
  -(defun material-pair-contact-normal (material-pair body)
  +(defn material-pair-contact-normal ((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:    material-b
     static-friction-coefficient
     kinetic-friction-coefficient)
    (values))
  
  (defun world-set-default-material-softness (world
                                              material-a
                                              material-b
                                              softness)
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (newtonmaterialsetdefaultsoftness
     (%world-ptr world)
     material-a
     material-b
     softness)
    (values))
  
  (defun world-set-material-pair-surface-thickness (world
                                                    material-a
                                                    material-b
                                                    thickness)
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (newtonmaterialsetsurfacethickness
     (%world-ptr world)
     material-a
     material-b
     thickness)
    (values))
  
  (defun material-contact-rotate-tangent-directions (material-pair vec3)
    (declare (optimize (speed 3) (safety 1) (debug 1)))
    (with-foreign-array (v3 vec3 '(:array :float 3))
      (newtonmaterialcontactrotatetangentdirections
       (%material-pair-ptr material-pair)
       v3)))
  
  (defun material-pair-contact-position-and-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
  