Efficient Shadows from Sampled Environment Maps
Efficient Shadows from Sampled Environment Maps
复制标题
来自采样环境贴图的高效阴影
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
Maneesh Agrawala
中科院分区：
文献类型：
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作者：
A. Ben;R. Ramamoorthi;Maneesh Agrawala
本文研究了环境地图中阴影的高效计算问题。由于从环境地图中精确渲染阴影需要数百个光源，因此昂贵的计算是确定从每个像素到每个光照方向的可见性，例如通过光线追踪。我们表明，空间和角域的相干性可以用来减少需要跟踪的阴影光线的数量。具体来说，我们对图像进行了从粗到精的评估，通过重用已经评估过的四个附近像素的可见性计算来预测可见性。这种简单的方法使我们能够明确地标记预测中的不确定区域。通过仅跟踪这些方向和邻近方向的光线，我们能够将跟踪的阴影光线数量减少20倍，同时保持错误率低于0.01%。对于许多场景，我们的算法可以从数百个灯光中添加阴影，其成本是无阴影渲染的两倍。
This paper addresses the problem of efficiently calculating shadows from environment maps. Since accurate rendering of shadows from environment maps requires hundreds of lights, the expensive computation is determining visibility from each pixel to each light direction, such as by ray-tracing. We show that coherence in both spatial and angular domains can be used to reduce the number of shadow rays that need to be traced. Specifically, we use a coarse-to-fine evaluation of the image, predicting visibility by reusing visibility calculations from four nearby pixels that have already been evaluated. This simple method allows us to explicitly mark regions of uncertainty in the prediction. By only tracing rays in these and neighboring directions, we are able to reduce the number of shadow rays traced by up to a factor of 20 while maintaining error rates below 0.01%. For many scenes, our algorithm can add shadowing from hundreds of lights at twice the cost of rendering without shadows.