|a: Base Texture||b: Normal Mapping||c: Relief Mapping|
In order to simulate additional geometry, that is not present in the basic building meshes generated by citygen, relief mapping is used. Normal mapping can be used as a solution to add detail to the shading of an object, notice how image b contains shadows and highlights for the window portions in contrast to image a. Relief mapping provides two major benefits in addition to normal mapping, namely the effects of parallax and occlusion, like the similar method of 'Parallax Occlusion Mapping'.
- Parallax: is the effect where the apparent position of an object changes with the observation point. This is illustrated in the diagram above where the windows on the left of building c appear behind the original window opening in contract to the other two.
- Occlusion: is the effect where an object is masked, hidden or occluded from view by an object that is closer to the observation point. This is illustrated on building c where the windows are no longer completely visible due to the occlusion provided by the walls.
With these benefits taken into account and by simply observing the results of each technique it is clear that relief mapping is a much better solution for simulating geometry than standard texturing and normal mapping techniques.