OpenGL 4 Shading Language Cookbook - Third Edition

How it works...

The first pass is fairly straightforward. We draw the entire scene normally, except we separate the ambient color from the diffuse and specular color, and send the results to different buffers.

The second pass is the core of the algorithm. Here, we render only the objects that cast shadows and let the geometry shader produce the shadow volumes. Thanks to the geometry shader, we don't actually end up rendering the shadow-casting objects at all, only the shadow volumes. However, before this pass, we need to do a bit of setup. We set up the stencil test so that it increments when a front face is rendered and decrements for back faces using glStencilOpSeparate, and the stencil test is configured to always succeed using glStencilFunc ...