- * The behavior of this option also depends on the SMOOTH_COLOR option and
- * whether or not the model has unique vertex normals; if SMOOTH_COLOR is
- * disabled, each triangle will be shaded a flat color. If it is enabled,
- * Gouraud interpolation is used to smooth the lighting across the face of
- * each triangle. See the PRE_NORMALS and SMOOTH_COLOR options.
+ * The behavior of this option is effected by its precise value:
+ * 1 Phong lighting model with flat (per-face) interpolation.
+ * 2 Phong lighting model with Gouraud (per-vertex) interpolation.
+ * 3 Phong lighting model with Phong (per-pixel) interpolation.