Raytracing prefiltered occlusion for aggregate geometry
Raytracing prefiltered occlusion for aggregate geometry
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DOI：
10.1109/rt.2008.4634616
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发表时间：
2008-09
期刊：
影响因子：
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通讯作者：
Dylan Lacewell;Brent Burley;Solomon Boulos;P. Shirley
中科院分区：
文献类型：
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作者：
Dylan Lacewell;Brent Burley;Solomon Boulos;P. Shirley
我们预过滤聚集几何体的遮挡，例如，树叶或头发，将局部遮挡存储为包围体层次（BVH）的每个节点中的方向不透明度。在相交过程中，我们根据光线微分在BVH节点处提前终止光线，并合成存储的不透明度。这使得交叉成本与具有大差异的射线的几何复杂性无关，同时降低了遮挡估计的方差。这两个算法的改进导致软阴影和环境光遮挡的显着性能增益。预过滤的不透明度数据仅取决于几何体，而不取决于灯光，并且可以基于关于聚合几何体统计信息的假设在线性时间内计算。
We prefilter occlusion of aggregate geometry, e.g., foliage or hair, storing local occlusion as a directional opacity in each node of a bounding volume hierarchy (BVH). During intersection, we terminate rays early at BVH nodes based on ray differential, and composite the stored opacities. This makes intersection cost independent of geometric complexity for rays with large differentials, and simultaneously reduces the variance of occlusion estimates. These two algorithmic improvements result in significant performance gains for soft shadows and ambient occlusion. The prefiltered opacity data depends only on geometry, not lights, and can be computed in linear time based on assumptions about the statistics of aggregate geometry.