Soft Textured Shadow Volume
Eurographics - Symposium on Rendering 2009, Girona, Spain
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Abstract
Efficiently computing robust soft shadows is a challenging and time consuming task. On the one hand, the quality of image-based shadows is inherently limited by the discrete property of their framework. On the other hand, object-based algorithms do not exhibit such discretization issues but they can only efficiently deal with triangles having a constant transmittance factor. This paper addresses this limitation. We propose a general algorithm for the computation of robust and accurate soft shadows for triangles with a spatially varying transmittance. We then show how this technique can be efficiently included into object-based soft shadow algorithms. This results in unified object-based frameworks for computing robust direct shadows for both standard and perforated triangles in fully animated scenes.
Illustration of shadows cast by perforated triangles (fences) using our soft textured shadow volume algorithm.
Three test scenes. From left to right: Factory: 582,510 triangles, 14 perforated triangles and 4 omni-directional lights; Greece: 1,396,078 triangles, 26,150 perforated triangles and 3 omni-directional lights; HL2: 84,712 triangles, 4,002 perforated triangles and 2 omni-directional lights.
Shadow comparison - Comparison between the shadows computed by the Penumbra Wedge+Soft Textured Shadow Volume algorithm (left), the Depth Complexity Sampling+Soft Textured Shadow Volume technique (middle) and a Ray Traced reference [Mental Ray] computed onto the fences represented by meshes (right).
Shadow comparison - Comparison between the shadows cast by a fence represented by perforated triangles (2 perforated triangles, Soft textured shadow volume: 90 FPS) (left) and by its corresponding mesh (233,358 triangles, Depth Complexity Sampling 16: 3.3 FPS) (right).