anchor.diff:                 (aref (image-data image) (+ 1 (* index bpp))) g
                  (aref (image-data image) (+ 2 (* index bpp))) b
                  (aref (image-data image) (+ 3 (* index bpp))) a)))))
  +
  +(defun image-get-pixel (image x y)
  +  (let ((index (+ x (* y (image-width image)))))
  +    (image-get-pixel/index image index)))
  +
  +(defun image-get-pixel/index (image index)
  +  (let ((bpp (image-bpp image)))
  +    (ecase bpp
  +      (1 (values (aref (image-data image) (* index bpp))
  +                 0 0 0))
  +      (2 (values (aref (image-data image) (* index bpp))
  +                 (aref (image-data image) (+ 1 (* index bpp)))
  +                 0 0))
  +      (3 (values (aref (image-data image) (* index bpp))
  +                 (aref (image-data image) (+ 1 (* index bpp)))
  +                 (aref (image-data image) (+ 2 (* index bpp)))
  +                 0))
  +      (4 (values (aref (image-data image) (* index bpp))
  +                 (aref (image-data image) (+ 1 (* index bpp)))
  +                 (aref (image-data image) (+ 2 (* index bpp)))
  +                 (aref (image-data image) (+ 3 (* index bpp))))))))
   
   ;;; 2D Texture
   (defstruct texture
  
positive.code: 
  ;;; Image
  (defstruct image
    width height bpp data)
  
  (defun create-image (width height bpp)
  
negative.code: 
  ;;; Bounding box
  (defstruct bbox
    "Axis Aligned Bounding Box."
    valid
    x-min y-min z-min
    x-max y-max z-max)
  