Normal Enhancement for Interactive Non-photorealistic Rendering

We present a simple technique to improve the perception of shape of an object. Bump mapping is well-known in the computer graphics community for providing the impression of small-scale geometrical features (which actually are not there). Here, we propose a similar approach (variation of normals) for the purpose of enhancing perception of the 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 cheap shading techniques can often generate shading ambiguities.