Bitmask Soft Shadows

  • Computer Graphics Group, University of Erlangen-Nuremberg
Eurographics 2007
Bitmask soft shadows (BMSS) directly track the visibility of points on a light source. They offer correct occluder fusion handling, avoiding noticeable overlapping artifacts (right), and can deal with multi-colored light sources, such as a two-colored EG logo light source (left).


Recently, several real-time soft shadow algorithms have been introduced which all compute a single shadow map and use its texels to obtain a discrete scene representation. The resulting micropatches are backprojected onto the light source and the light areas occluded by them get accumulated to estimate overall light occlusion. This approach ignores patch overlaps, however, which can lead to objectionable artifacts. In this paper, we propose to determine the visibility of the light source with a bit field where each bit tracks the visibility of a sample point on the light source. This approach not only avoids overlapping-related artifacts but offers a solution to the important occluder fusion problem. Hence, it also becomes possible to correctly incorporate information from multiple depth maps. In addition, a new interpretation of the shadow map data is suggested which often provides superior visual results. Finally, we show how the search area for potential occluders can be reduced substantially.


Schwarz, M., Stamminger, M. 2007. Bitmask soft shadows. Computer Graphics Forum, 26, 3 (Proceedings of Eurographics 2007), 515–524
    author  = {Michael Schwarz and Marc Stamminger},
    title   = {Bitmask Soft Shadows},
    journal = {Computer Graphics Forum},
    volume  = {26},
    number  = {3} # { (Proceedings of Eurographics 2007)},
    year    = {2007},
    month   = sep,
    pages   = {515-524}