Cel shading

Cel shading (often misspelled as 'cell shading') or toon shading is a type of non-photorealistic rendering designed to make 3-D computer graphics appear to be flat by using less shading color instead of a shade gradient or tints and shades. Cel-shading is often used to mimic the style of a comic book or cartoon and/or give it a characteristic paper-like texture. There are similar techniques that can make an image look like a sketch, an oil painting or an ink painting. It is somewhat recent, appearing from around the beginning of the twenty-first century. The name comes from cels (short for celluloid), the clear sheets of acetate which are painted on for use in traditional 2D animation.

Process

The cel-shading process starts with a typical 3D model. Where cel-shading differs from conventional rendering is in its non-photorealistic illumination model. Conventional (smooth) lighting values are calculated for each pixel and then quantized to a small number of discrete shades to create the characteristic flat look – where the shadows and highlights appear more like blocks of color rather than mixed in a smooth way.