anchor.diff:        (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 triangles filled-triangles)
  -       for ebo in (cddr ebos)
  +    (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)
  
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:draw-elements :lines (gl:make-null-gl-array :unsigned-int) :count (length lines)))
  
        (when (> (length triangles) 0)
          (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)
  