anchor.diff:          (b (coerce y 'single-float))
           (c (coerce z 'single-float)))
       (vector a b c 1.0)))
  -
  -;; (defmethod MFColor (x y z)
  -;;   (let ((a (coerce x 'single-float))
  -;;         (b (coerce y 'single-float))
  -;;         (c (coerce z 'single-float)))
  -;;     (cl:vector a b c 1.0)))
   
   ;; ----------------------------------------------------------------------------
   (defmethod IntensityType(str)
  
positive.code:               (- zfar znear)))
          (f (/ (* -2 znear zfar)
                (- zfar znear))))
      (sb-cga:matrix   a  0.0     c  0.0
                     0.0    b     d  0.0
                     0.0  0.0     e    f
                     0.0  0.0  -1.0  0.0)))
  
  ;; ----------------------------------------------------------------------------
  (defun perspective (fov aspect znear zfar)
    (let* ((ymax (SFFloat (* znear
                            (tan (radians (SFFloat (/ fov 2)))))))
           (ymin (- ymax))
           (xmin (* ymin aspect))
           (xmax (* ymax aspect)))
  
negative.code: 
  (in-package #:cl-3d)
  
  ;; ----------------------------------------------------------------------------
  (defun radians (x)
    (declare (single-float x))
    (* x (/ pi 180)))
  
  ;; ----------------------------------------------------------------------------
  (defun degrees (x)
    (declare (single-float x))
    (* x (/ 180 pi)))
  
  ;; ----------------------------------------------------------------------------
  (defun transform (translation center rotation scale scaleOrientation)
    (let ((C (sb-cga:translate center))
          (R (apply #'sb-cga:rotate-around rotation))
          (S (sb-cga:scale scale))
          (SR (apply #'sb-cga:rotate-around scaleOrientation))
          (Tx (sb-cga:translate translation)))
      (let ((-SR (sb-cga:inverse-matrix SR))
            (-C (sb-cga:inverse-matrix C)))
        (sb-cga:matrix* Tx C R SR S -SR -C))))
  
  ;; ----------------------------------------------------------------------------
  (defun frustum (xmin xmax ymin ymax znear zfar)
  