Variance shadow maps
Variance shadow maps
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DOI：
10.1145/1111411.1111440
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发表时间：
2006-03
期刊：
影响因子：
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通讯作者：
William Donnelly;Andrew Lauritzen
中科院分区：
文献类型：
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作者：
William Donnelly;Andrew Lauritzen
阴影贴图是一种在实时图形中广泛应用的阴影技术。使用它们的一个主要缺点是它们不能像颜色纹理那样过滤，通常会导致严重的混叠。本文介绍了一种新的实时阴影算法——方差阴影映射。我们不是存储单个深度值，而是存储深度分布的均值和均方，从中我们可以有效地计算任何过滤区域上的方差。使用方差，我们推导出被遮挡的阴影片段的分数的上界。我们表明，这个边界通常提供了一个很好的近似真实遮挡，并且可以用作渲染的近似值。我们的算法在当前的图形处理器上易于实现，并且以最小的额外存储和计算解决了阴影地图混叠问题。
Shadow maps are a widely used shadowing technique in real time graphics. One major drawback of their use is that they cannot be filtered in the same way as color textures, typically leading to severe aliasing. This paper introduces variance shadow maps, a new real time shadowing algorithm. Instead of storing a single depth value, we store the mean and mean squared of a distribution of depths, from which we can efficiently compute the variance over any filter region. Using the variance, we derive an upper bound on the fraction of a shaded fragment that is occluded. We show that this bound often provides a good approximation to the true occlusion, and can be used as an approximate value for rendering. Our algorithm is simple to implement on current graphics processors and solves the problem of shadow map aliasing with minimal additional storage and computation.