anchor.diff:  
   (defun collada-parse-vertices (dom node)
     (assert (string= (dom:tag-name node) "vertices"))
  -  (let ((input (collada-node-singleton node "input")))
  +  (let ((input (dom-select-tag node "input" :direct t :singleton t)))
       (assert (and (dom:has-attribute input "semantic")
                    (string= (dom:get-attribute input "semantic")
                             "POSITION")))
  
positive.code:   (substitute #\_ #\- collada-identifier))
  
  (defun collada-povray-geometry (dom geometry-node modifiers)
    (let* ((mesh  (collada-node-singleton geometry-node "mesh"))
           (polylist  (collada-node-singleton mesh "polylist"))
           (prim  (collada-node-integers (collada-node-singleton polylist "p")))
           (vcount  (collada-node-integers (collada-node-singleton polylist "vcount")))
           (inputs (dom:get-elements-by-tag-name polylist "input"))
           (vertices)
           (normals))
  
negative.code: (defun collada-povray (&key
                           (dom *collada-dom*)
                           file)
    (let* ((result (pov-sequence
                   (let* ((node (dom-select-tag dom "library_visual_scenes" :singleton t)))
                     (collada-povray-visual-scene dom node)))))
      (if file
          (with-open-file (s file :direction :output :if-exists :supersede)
  