At one point or another, you may find yourself in a situation where one or more lights show some sort of shadow corruption. In this situation it is very helpful to see what is stored in the shadow map in order to determine if the source of the corruption is in the shadow map generation step or in the lighting step.
Shadow map's value range is higher than the 8 bit per pixel that your monitor can display. When just outputting the depth value stored in a shadow map, you are very likely to end up with a gray image that has very low contrast values. In most cases, it will be hard to figure out what is in the shadow map with this form of visualization.
One way to improve the contrast of the shadow map content is to highlight the silhouettes of the shadow map content, which will result in a nice visual outline around the objects. In this recipe we will implement this kind of visualization mode using a very simple technique.