A very simple implementation of cell shading is to run the result of traditional lighting through a lookup table in the form of a 1D texture. Having runs and s

A very simple implementation of cell shading is to run the result of traditional lighting through a lookup table in the form of a 1D texture. Having runs and steps of solid color posterizes the smooth lighting input so that it resembles painted cell artwork. A very simple implementation of outlining is to draw the object a second time solid black, with the vertex positions extruded out in the direction of the vertex normals, and with backface culling flipped so that you see only internal faces. Those black, internal faces peeking out around the edge of the regular mesh form the outlines. That's a good starting point. Many iterations and improvements from there gets you to this: https://www.youtube.com/watch?v=yhGjCzxJV3E https://www.youtube.com/watch?v=yhGjCzxJV3E