Real-world objects and scenarios are not only defined by their geometry, shape, and structure. We are also very sensitive to the look and texture, and how light interacts with the different materials. Imagine a beach with no sand texture or a wavy sea that did not reflect sunlight properly. A huge part of an object's essence lies within its shading properties, and that is what this chapter is all about.
In computer graphics, shading is a very broad term used to represent all the processes involved in assigning colors to pixels, which in turn represent geometry. Shading is usually divided into two large areas: material synthesis and illumination. Material synthesis deals with textures and surface properties, and illumination handles light and shadows. This chapter deals with the illumination component, whereas the next chapter is devoted to texture-based techniques.
Be warned, though: These are lengthy subjects, and hundreds of pages could be devoted to them. Hopefully, these chapters will show you the core routines, and your imagination and personal research will take care of the rest.