shadow volume - non-manifold objects

I have doubts regarding the crea开发者_C百科tion of shadow volumes for non-manifold objects, specially when the objects have dangling faces.

For instance:

_{(source: ricfow at www.dt.fee.unicamp.br)}

where we have a box (brown) and two connected faces (white) on the top. The standard z-pass and z-fail algorithms fail to produce correct shadows. Where can I find theoretical material to improve the standard algorithms to cope with more complex cases (as the one above)?

The paper: A Shadow Volume Algorithm for Opaque and Transparent Non-Manifold Casters, B. Kim, K. Kim and G. Turk, Journal of Graphics Tools, 13(3):1-14, 2008

presents interesting improvements to cope with non-manifold geometry. The geometry presented in the above picture can be handled by the proposed approach.

Best regards, ricfow