Color Ramps

Having established a basic technique for lighting our object we can now move on to the task of creating variations across the surface. In this chapter we introduce the most basic of such variations—a ramp of color changing smoothly from one side of the object to the other. Though the whole process of calculating the color of a surface point is referred to as shading, and in RenderMan any custom code written in SL is known as a shader, the term shading more strictly refers to the calculation of the interaction of light with the surface. Though a little clichéd the standard plastic model provides reasonable flexibility when used intelligently and (at least in the short-term) we can consider the actual shading part of our shader done. In fact what most shaders are concerned with is the variation of properties such as color and roughness, across the surface—variation which we will refer to as texturing. It is these variations which create visual interest, and make rendered images spring to life rather than appearing dull and artificial.