›› 2012, Vol. 42 ›› Issue (04): 971-978.

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Algorithm for rendering physically correct soft shadows based on ambient occlusion masks

CHEN Chun-yi1,2, YANG Hua-min2, LI Wen-hui1, JIANG Zhen-gang2   

  1. 1. College of Computer Science and Technology, Jilin University, Changchun 130012, China;
    2. School of Computer Science and Technology, Changchun University of Science and Technology, Changchun 130022, China
  • Received:2011-06-22 Online:2012-07-01 Published:2012-07-01

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Abstract: Focusing on the problem of rendering physically correct soft shadows, a method is proposed which uses occlusion masks to evaluate the visibility of an area light source. Prior to the rendering process, a cube map of ambient occlusion masks is computed. In the rendering process, the cube map is employed to compute the ambient occlusion masks of triangles intersecting with a rectangular pyramid, which is used as the bounding volume for light-source sample rays in the visibility testing. Then the "and" bitwise operations are carried out on these ambient occlusion masks. Finally, based on the results of the bitwise operations, the blocking-distance testing is further utilized to determine which light-source sample rays are not blocked. Compared with the lighting computation method via Monte Carlo integration, the proposed method can not only render physically correct soft shadows, but also avoid a large number of intersection-testing operations for shadow rays. This advantage can enhance the efficiency in solving the rendering equation.

Key words: computer application, soft shadows, ambient occlusion, light-source visibility, rendering equation

CLC Number: 

  • TP301.6
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