anchor.diff:          (gl:draw-elements :lines (gl:make-null-gl-array :unsigned-int) :count (length lines)))
   
         (when (> (length triangles) 0)
  -        (gl:bind-buffer :array-buffer (cadr vbos))
  +        (gl:bind-buffer :array-buffer (car vbos))
           (use-program line-program transformation viewport)
           (gl:bind-buffer :element-array-buffer (triangle-ebo ebos))
           (gl:polygon-mode :front-and-back :line)
  
positive.code:       (gl:buffer-data :array-buffer :dynamic-draw gl-vertices)
        (gl:free-gl-array gl-vertices))
  
      (loop for indices in (list points lines)
         for ebo in ebos
         do
           (let ((gl-indices (to-gl-array indices :unsigned-int)))
  
negative.code:       (gl:bind-buffer :array-buffer (cadr vbos))
        (gl:buffer-data :array-buffer :dynamic-draw gl-vertices)
        (gl:free-gl-array gl-vertices))
      (loop for indices in (list filled-triangles)
         for ebo in (cdddr ebos)
         do
           (let ((gl-indices (to-gl-array indices :unsigned-int)))
             (gl:bind-buffer :element-array-buffer ebo)
  