Chapter 18. Non-Photorealistic Shaders
A significant amount of computer graphics research has been aimed at achieving more and more realistic renditions of synthetic scenes. A longtime goal has been to render a scene so perfectly that it is indistinguishable from a photograph of the real scene, hence the term PHOTOREALISM. With the latest graphics hardware, some photorealistic effects are becoming possible in real-time rendering.
This quest for realism is also reflected in graphics APIs such as OpenGL. The OpenGL specification defines specific formulas for calculating effects such as illumination from light sources, material properties, and fog. These formulas attempt to define effects as realistically as possible while remaining relatively easy to implement in hardware, and they have duly been cast into silicon by intrepid graphics hardware designers.
But the collection of human art and literature shows us that photorealism is not the only important style for creating images. The availability of low-cost programmable graphics hardware has sparked the growth of an area called NON-PHOTOREALISTIC RENDERING, or NPR. Researchers and practitioners in this field are attempting to use computer graphics to produce a wide range of artistic effects other than photorealism. In this chapter, we look at a few examples of shaders whose main focus is something other than generating results that are as realistic as possible.