A cow smiley. All images in this section are by Mariana Ruiz Villarreal (a.k.a. LadyofHats). This tutorial covers toon shading (also known as cel shading) as an example of non-photorealistic rendering techniques. It is one of several tutorials about lighting that go beyond the Phong reflection model. However, it is based on per-pixel lighting with the Phong reflection model as described in Section