OpenGL Insights

274 III Bending the Pipeline

Figure 19.8. The total GPU time required to render 1 to 32 shadow maps (left) and the average GPU time

required per shadow map (right) using traditional shadow map generation (blue), our layered method without

back-face culling (red) and our layered method with back-face culling (green). Lower values are better.

geometry shader in Listing 19.10. The rest of the configuration is equivalent to the

one used in the first test; we use the minimalistic vertex shader show in Listing 19.6

and only a single instance of the scene.

As shown in Figure 19.8, if we use back-face culling, the rendering time is almost

halved, a nd the GPU ...