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.