anchor.diff:  ;; Possible problem: what if a rectangle disappears? How to remove it from
   ;; the sequential hash-table?
   
  -;; TODO: texatl to get sprites and spritesheet integretation, maybe even text!!
  +;; TODO: texatl to get sprites and spritesheet integration, maybe even text!!
   
   ;; one big texture to read all the data from, again using texatl?
   
  
positive.code:    (y1 :initarg :y1 :type vec3)
     (y2 :initarg :y2 :type vec3)))
  
  ;; TODO: make super-class rectangle and sub-class pic-object. Seperating rendering
  ;;       representation from interior representation and proxy geometry for collision
  ;;       tests
  ;; UPDATE: maybe go with the superclass: rectangle, subclass: pic-object approach, which
  ;;         will contain a representation slot (e.g. filled with sphere, rectangle), an
  ;;         <animation> slot a proxy geometry, a cached geometry (past timesteam when no
  ;;         collision orientation)
  (defclass rectangle (parallelogram)
    ;; TODO: instead of vec2 provide as seperate x1-x x1-y ? So that
    ;;       transforming into 1d-array is easier (to pass into foreign-array)
    (;; center-radius representation
     (center-point :initarg :center-point :type vec3)
  
negative.code: 				   ;; NEXT-TODO DOT-PRODUCT is the culprit!
  				   ;; rotation beyond 180-degree doesn't work
  				   ;; with this properly!
  				   ;; SOLUTION: (IF (CROSS-PRODUCT ...)
  				                    ;; <this was around>
  						    ;; <other way around>)
  				   ;; add tighter BV to nyo initialisation for
  				   ;; more intuitive collision testing
  				   (sb-cga:dot-product (vec3 0.0 1.0 0.0)
  						       up-dir))))
  