Multipoint Silhouette Determination

I have developed multipoint silhouette determination on CPU with volume extrusion in the geometry shader. The reason why CPU is used is that geometry shader uses adjacency faces for silhouette determination, but for efficient implementation we need to iterate over mesh edges and see the orientation of their left and right adjacent faces that geometry shader can't do. The problem can be solved using compute shader with arbitrary data layout, but my laptop GPU is capable only of SM 4.1.

Of course with each additional light sample the shadow volume overdraw is significantly increased.

Rectangular Light Source

The last few days I was in the debugging of penumbra shaders for rectangular light source. All my previous soft shadows implementations supported spherical light sources only and with rectagular light there was an incorrect shading. In the end I wrote a shader algorithm in C++ and debugged a few test cases. It turned out that the correct solution requires inverting 3x3 matrix directly in the pixel shader, which in the original implementation of the algorithm I haven't seen. Software implementation helped to understand all the subtleties of the algorithm (that's almost impossible with HLSL and GPU-oriented tools).

Due to low-poly geometry and rectangular shape of light source penumbra looks a bit angular. But the major problem is "single point silhouette approximation", I've written about it here (sorry, in russian). Because of this simplification the shadow looks like overshadowed, because not all potential silhouette edges contributed to penumbra. I don't like how the shadow looks, so I plan to implement more sophisticated silhouette edges determination.