anchor.diff:                                      (output-directory *robray-tmp-directory*)
                                       ;(pov-file "frame")
                                       (frame-start 0)
  +                                    append
                                       (scene-graph *scene-graph*)
                                       (width *width*)
                                       (height *height*)
  
positive.code:                                     (frames-per-second *frames-per-second*)
                                      include)
    (ensure-directories-exist output-directory)
    (map nil #'delete-file (frame-files output-directory))
    ;; Write frames
    (loop
       for frame from frame-start
  
negative.code: 
  (defun frame-files (directory)
    (directory (concatenate 'string directory "/*.pov")))
  
  (defun last-frame-number (files)
    (frame-number (car (last (sort-frames files)))))
  
  (defun animate-encode (&key
                           (directory *robray-tmp-directory*)
  