HLSL Development Cookbook

Multiple light types in a single pass

In this chapter's introduction, we saw that the performance can be optimized by combining multiple lights into a single draw call. The GPU registers are big enough to contain four float values. We can take advantage of that size and calculate four lights at a time.

Unfortunately, one drawback of this approach is the lack of support for projected textures. One way around this issue is to render light sources that use projected textures separately from the rest of the light sources. This limit may not be all that bad depending on the rendered scene light setup.

Getting ready

Unlike the previous examples, this time you will have to send light data to the GPU in groups of four. Since it's not likely that all four ...