Shadows add a great deal of realism to a scene. Without shadows, it can be easy to misjudge the relative location of objects, and the lighting can appear unrealistic, as light rays seem to pass right through objects.
Shadows are important visual cues for realistic scenes, but can be challenging to produce in an efficient manner in interactive applications. One of the most popular techniques for creating shadows in real-time graphics is the shadow mapping algorithm (also called depth shadows). In this chapter, we'll look at several recipes surrounding the shadow mapping algorithm. We'll start with the basic algorithm, and discuss it in detail in the first recipe. Then we'll look at a couple of techniques for improving the look of the shadows produced by the basic algorithm.
We'll also look at an alternative technique for shadows called shadow volumes. Shadow volumes produce near perfect hard-edged shadows, but are not well suited for creating shadows with soft edges.