Interactive Shadow Generation in Complex Environments

by Naga Govindaraju, Brandon Lloyd, Sung-Eui Yoon, Avneesh Sud and Dinesh Manocha.

Architecture of the Process-Parallel Algorithm: This figure highlights different components of our hybrid shadow generation algorithm. Each color represents a separate graphics processor or CPU.

We present a new algorithm for interactive generation of hard-edged, umbral shadows in complex environments with a moving light source. Our algorithm is based on a hybrid approach that combines some of the efficiencies of image-precision techniques along with the image quality of object-precision methods. We present interactive algorithms based on levels-of-detail (LODs) and visibility culling to compute the potential shadow-casters and shadow-receivers. We further reduce their size based on a novel cross-visibility culling algorithm. Finally, we use a combination of shadow polygons and shadow maps to generate shadows. We also present techniques for LOD-selection that eliminate the artifacts in self-shadows. Our algorithm can generate sharp shadow edges and reduce aliasing. We have implemented the algorithm on a three PC system with NVIDIA GeForce-4 cards and applied it to three complex environments composed of millions of triangles. It can render the scene and generate shadows at 7-25 frames per second on these models.

The left image shows a snapshot generated from the application of our hybrid shadow generation algorithm to the power plant model (12.7M triangles). The middle image shows a different viewpoint generated using perspective shadow maps. Notice the aliasing artifacts. The right image highlights the shadows generated by our interactive algorithm from the same viewpoint with sharper boundaries.


Interactive Shadow Generation in Complex Environments UNC Computer Science Technical Report TR03-004, 2003. To appear in Proc. of ACM SIGGRAPH 2003

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CB #3175, Department of Computer Science
University of North Carolina
Chapel Hill, NC 27599-3175