“Sub-pixel shadow mapping” by Lecocq, Gautron, Marvie and Sourimant

The limited resolution of shadow maps may result in erroneous shadowing, yielding artificially jagged edges (Figure 1) and temporally crawling shadows even using perspective optimization techniques. Dai et al. [2008] propose an explicit storage of geometry within shadow map texels to avoid aliasing. Each texel stores the coordinates of the closest triangle only, potentially leading to false negatives in the intersection computation while incurring large memory consumption. These artifacts are reduced by intersecting the triangles stored in numerous neighboring texels, resulting in significant performance hit while still missing some intersections. We introduce Sub-Pixel Shadow Maps (SPSM) for real-time shadow mapping with sub-pixel precision. Our technique is based on the storage of a fixed-size partial representation of the scene geometry using conservative rasterization, combined with an original reconstruction of shadow edges.

1. Dai, Q., Yang, B., and Feng, J. 2008. Reconstructable geometry shadow maps. In Proceedings of I3D, 4:1–4:1.
2. Hasselgren, J., Akenine-Möller, T., and Ohlsson, L. 2005. Conservative rasterization. In GPU Gems 2, M. Pharr, Ed. Addison-Wesley, 677–690.