anchor.diff:  ;;------------------------------------------------------------
   ;; NewtonSkeletonContainer* - newtonskeletoncontainer - skeleton
   
  -(deftclass (skeleton (:constructor %make-skeleton)
  +(defstruct (skeleton (:constructor %make-skeleton)
                     (:conc-name %skeleton-))
     (ptr (error "") :type foreign-pointer))
   
   ;;------------------------------------------------------------
   
  -(deftclass (mesh (:constructor %make-mesh)
  +(defstruct (mesh (:constructor %make-mesh)
                        (:conc-name %mesh-))
     (ptr (error "") :type foreign-pointer))
   
   ;;------------------------------------------------------------
   
  -(deftclass (joint (:constructor %make-joint)
  +(defstruct (joint (:constructor %make-joint)
                     (:conc-name %joint-))
     (ptr (error "") :type foreign-pointer))
   
  -(deftclass (ball-&-socket (:constructor %make-ball-&-socket) (:include joint)))
  +(defstruct (ball-&-socket (:constructor %make-ball-&-socket) (:include joint)))
   
  -(deftclass (corkscrew (:constructor %make-corkscrew) (:include joint)))
  +(defstruct (corkscrew (:constructor %make-corkscrew) (:include joint)))
   
  -(deftclass (hinge (:constructor %make-hinge) (:include joint)))
  +(defstruct (hinge (:constructor %make-hinge) (:include joint)))
   
  -(deftclass (slider (:constructor %make-slider) (:include joint)))
  +(defstruct (slider (:constructor %make-slider) (:include joint)))
   
  -(deftclass (universal-joint (:constructor %make-universal-joint)
  +(defstruct (universal-joint (:constructor %make-universal-joint)
                               (:include joint)))
   
  -(deftclass (up-vector (:constructor %make-up-vector) (:include joint)))
  +(defstruct (up-vector (:constructor %make-up-vector) (:include joint)))
   
   ;; An advanced feature we dont need yet
  -;; (deftclass (bilateral-joint (:constructor %make-bilateral-joint)
  +;; (defstruct (bilateral-joint (:constructor %make-bilateral-joint)
   ;;                             (:include joint)))
   
   ;;------------------------------------------------------------
   
  -(deftclass (material-pair (:constructor %make-material-pair)
  +(defstruct (material-pair (:constructor %make-material-pair)
                        (:conc-name %material-pair-))
     (ptr (error "") :type foreign-pointer))
   
  
positive.code: (defun gen-world-id ()
    (incf *world-id*))
  
  (deftclass (world (:constructor %make-world)
                    (:conc-name %world-))
    (ptr (error "") :type foreign-pointer)
    (id (gen-world-id) :type (unsigned-byte 16))
  
negative.code: 
  ;;------------------------------------------------------------
  
  (defstruct (geometry (:constructor %make-geometry)
                       (:conc-name %geometry-))
    (ptr (error "") :type foreign-pointer))
  
  (defstruct (null-geometry
              (:constructor %make-null)
              (:include geometry))
    (iterator-callback  ))
  
  (defstruct (box-geometry
              (:constructor %make-box)
              (:include geometry)))
  
  (defstruct (sphere-geometry
              (:constructor %make-sphere)
              (:include geometry)))
  
  (defstruct (cone-geometry
              (:constructor %make-cone)
              (:include geometry)))
  
  (defstruct (capsule-geometry
              (:constructor %make-capsule)
              (:include geometry)))
  
  (defstruct (cylinder-geometry
              (:constructor %make-cylinder)
              (:include geometry)))
  
  (defstruct (chamfer-cylinder-geometry
              (:constructor %make-chamfer-cylinder)
              (:include geometry)))
  
  (defstruct (convex-hull-geometry
              (:constructor %make-convex-hull-geometry)
              (:include geometry)))
  
  (defstruct (geometry-tree
              (:constructor %make-geometry-tree)
              (:include geometry)))
  
  (defstruct (compound-geometry
              (:constructor %make-compound-geometry)
              (:include geometry)))
  
  (defstruct (height-field-geometry
              (:constructor %make-height-field)
              (:include geometry)))
  
  (defstruct (scene-geometry
              (:constructor %make-scene)
              (:include geometry)))
  
  