anchor.diff:    (r02 0.0) (r12 0.0) (r22 1.0) (z2 0.0)
     (tx 0.0) (ty 0.0) (tz 0.0) (one 1.0))
   
  -(defconstant +matrix-identity+
  +(define-constant +matrix-identity+
     #(1.0 0.0 0.0 0.0
       0.0 1.0 0.0 0.0
       0.0 0.0 1.0 0.0
  
positive.code: (defstruct (axis (:type (vector float))
                   (:include vector-3d)))
  
  (defconstant +x-axis+ #(1.0 0.0 0.0))
  (defconstant +y-axis+ #(0.0 1.0 0.0))
  (defconstant +z-axis+ #(0.0 0.0 1.0))
  
  ;;; Quaternions
  (defstruct (quaternion (:type (vector float))
  
negative.code:         (basis-r20 basis) 0.0
          (basis-r21 basis) 0.0))
  
  (define-constant +basis-sin-precision+ 0.999999999) ;; 1.0-1.0e-9
  
  ;;      _                                _
  ;;     |  c2c3  s1s2c3-c1s3  s1s3+c1s2c3  |  s1,c1 : roll
  