A simple normal enhancement technique for interactive non-photorealistic renderings

We present a simple technique to improve the perception of an object's shape. Bump mapping is well known in the computer graphics community for providing the impression of small-scale geometrical features, which are not explicitly modelled. Here, we propose a similar approach (variation of normals) for the purpose of enhancing the perception of a given geometry. Our approach is based on a simple modification of the surface normals in order to enhance the geometric features of the object during the rendering. The enhanced normals produced by this approach can be used in any rendering technique. The technique presented is particularly well suited to improve the rendering of mechanical parts where common straightforward shading techniques can often generate shading ambiguities.