Controlling the dark side in toon shading

@inproceedings{Gulbrandsen2010ControllingTD,
  title={Controlling the dark side in toon shading},
  author={Ole Gulbrandsen},
  booktitle={SIGGRAPH Posters},
  year={2010}
}
Sharply separating a diffuse surface into a light and dark side often results in unwanted details. Combining normals from the actual surface with the normals from a simplified surface we get better control of the dark side.