Gooch shading

It is also known as "cool to warm" shading, and is widely used in technical illustration.

Gooch shading was developed by Amy Gooch et al. at the University of Utah School of Computing and first presented at the 1998 SIGGRAPH conference.

[1][2] It has since been implemented in shader libraries, software, and games released by Autodesk, NVIDIA, and Valve.

This allows shading to occur only in mid-tones so that edge lines and highlights remain visually prominent.

The Gooch shader is typically implemented in two passes: all objects in the scene are first drawn with the "cool to warm" shading, and in the second pass the object’s edges are rendered in black.