anchor.diff:  ;;opticl experiments------------------------------------------------------------
   
   ;; TODO: chedk out 3bgl-opticl for a direct solution
  -
  +;; TODO: check out sbcl for some lowlevel vecor access and provide it with
  +;;       #+sbcl.. ?
   (defun 3d-array->vector (3d-array)
     (let* ((dims (array-dimensions 3d-array))
   	 (dims-1d (apply #'* dims))
  
positive.code: 
  
  
  (defvar *123-image-object* (image-file->image-object "123.png"))
  
  ;; the sdl-surface is a struct-object
  ;; (sdl2-ffi::sdl-surface-ptr *123-PNG-SDL-SURFACE*) ==> ptr
  
negative.code: 
  	 (uniform :int :test-texture *tex-unit-2*)
  
  	 (with-slots (width height pixels ffi-array) *png-opticl*
  	   (gl:tex-image-2d :texture-2d 0 :rgba8
  			    width
  			    height 0
  			    :rgba	;components per element
  			    :unsigned-byte ;; normalized integer
  			    ffi-array))))))
  
  (defun draw-cube ()
    (gl:bind-vertex-array *vao*)
  