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Efficient Screen Space Anisotropic Blurred Soft Shadows

Zhongxiang ZHENG
Suguru SAITO

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E97-D    No.8    pp.2038-2045
Publication Date: 2014/08/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E97.D.2038
Type of Manuscript: Special Section PAPER (Special Section on Cyberworlds)
Category: Rendering
Keyword: 
computer graphics,  shadow mapping,  soft shadow,  screen space,  real time rendering,  

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Summary: 
Shadow mapping is an efficient method to generate shadows in real time computer graphics and has broad variations from hard to soft shadow synthesis. Soft shadowing based on shadow mapping is a blurring technique on a shadow map or on screen space. Blurring on screen space has an advantage for efficient sampling on a shadow map, since the blurred target array has exactly the same coordinates as the screen. However, a previous blurring method on screen space has a drawback: the generated shadow is not correct when a view direction has a large angle to the normal of the shadowed plane. In this paper, we introduce a new screen space based method for soft shadowing that is fast and generates soft shadows more accurately than the previous screen space soft shadow mapping method. The resultant images show shadows produced by our method just stand in the same place, while shadows by the previous method change in terms of penumbra while the view moves. Surprisingly, although our method is more complex than the previous method, the measurement results of the calculation time show our method is almost the same performance. This is because it controls the blurring area more accurately and thus successfully reduces multiplications for blurring.


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