anchor.diff:    (with-slots (radius solid) self
       (let ((radius (SFFloat radius))
             (solid (SFBool solid)))
  -        (gl:with-pushed-matrix
  -      (gl:rotate -90 1 0 0)
  -      (if solid
  -          (glut:solid-sphere radius 30 30)
  -          (glut:wire-sphere radius 30 30))))))
  +      (gl:with-pushed-matrix
  +        (gl:rotate -90 1 0 0)
  +        (if solid
  +            (glut:solid-sphere radius 30 30)
  +            (glut:wire-sphere radius 30 30))))))
   
   ;; (let* ((+x (abs (/ (elt size 0) 2)))
   ;;        (+y (abs (/ (elt size 1) 2)))
  
positive.code:           (bottom (SFBool bottom))
            (top (SFBool top))
            (solid (SFBool solid)))
          (gl:with-pushed-matrix
        (gl:rotate -90 1 0 0)
        (gl:translate 0 0 (- (/ height 2)))
        (glut:solid-cylinder radius height 20 1)))))
  
  
  ;; ......................................................................Sphere
  
negative.code:           (bottom (SFBool bottom))
            (solid (SFBool solid)))
        (gl:with-pushed-matrix
          (gl:rotate -90 1 0 0)
          (gl:translate 0 0 (- (/ height 2)))
          (if solid
              (glut:solid-cone bottomRadius height 20 1)                   ; shape
              (glut:wire-cone bottomRadius height 20 1))))))
  
  ;; ....................................................................Cylinder
  (defmethod run ((self Cylinder))
  