“Real-time soft shadows with cone culling” by Bavoil and Silva

  • ©Louis Bavoil and Claudio T. Silva




    Real-time soft shadows with cone culling



    We have developed a new physically-based technique for computing soft shadows from a shadow map for spherical lights. Shadow-map samples unprojected into world-space (micro-patches) are culled against a shadow cone wrapping all the possible shadow rays from the light to the surface location. Because of this volumetric test, the algorithm handles self-shadowing more robustly than traditional shadow mapping. The amount of shadowing contributed by each culled micro-patch is approximated by the solid angle subtended by the bounding sphere of the micro-patch over the solid angle of the light source. We describe a real-time implementation running entirely on a GPU. For each image pixel to shadow, the algorithm projects the pixel onto the near plane of the light frustum, and looks up occluding micro-patches in a dynamic disk kernel. To guarantee constant frame rates, the kernel is sampled using a fixed number of samples per pixel. Our results compare favorably to ray-tracing for images with no overlapping shadows.


    1. Atty, L., Holzschuch, N., Lapierre, M., Hasenfratz, J.-M., Hansen, C., and Sillion, F. 2006. Soft shadow maps: Efficient sampling of light source visibility. Computer Graphics Forum. (to appear).
    2. Bunnell, M. 2005. Dynamic ambient occlusion and indirect lighting. In GPU Gems 2, M. Pharr, Ed. Addison Wesley, ch. 14, 223–233.
    3. Dachsbacher, C., and Stamminger, M. 2005. Reflective shadow maps. In SI3D ’05: Proceedings of the 2005 symposium on Interactive 3D graphics and games.

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