anchor.diff:  
   (defun context-add-cylinder (context parent name tf length radius axis
                                &key
  +                               no-shadow
                                  (color '(0 0 0))
                                  (alpha 1d0)
                                  (collision t)
                                  (visual t))
     ;; Scene Graph
     (context-add-geometry context parent name tf (robray::scene-cylinder length radius axis)
  +                        :no-shadow no-shadow
                           :color color :alpha alpha
                           :collision collision :visual visual)
     (when collision
  
positive.code:                                   name
                                    (robray::make-scene-visual :geometry geometry
                                                               :color color
                                                               :alpha alpha)))))
  
  (defun context-add-sphere (context parent name tf radius &key
                                                             (color '(0 0 0))
                                                             (alpha 1d0)
                                                             (collision t)
                                                             (visual t))
    ;; Scene Graph
    (context-add-geometry context parent name tf (scene-sphere radius)
                          :color color :alpha alpha
                          :collision collision :visual visual)
    ;; Move It Scene
  
negative.code:                                name color alpha)))
  
  (defun context-add-box (context parent name tf dimensions &key
                                                             no-shadow
                                                              (color '(0 0 0))
                                                              (alpha 1d0)
                                                              (collision t)
                                                              (visual t))
    ;; Scene Graph
    (context-add-geometry context parent name tf (scene-box dimensions)
                          :no-shadow no-shadow
                          :color color :alpha alpha
                          :collision collision :visual visual)
    ;; Move It Scene
  