Accurate Shadows by Depth Complexity Sampling
Accurate Shadows by Depth Complexity Sampling
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DOI：
10.1111/j.1467-8659.2008.01164.x
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发表时间：
2008-04
影响因子：
2.5
通讯作者：
Vincent Forest;L. Barthe;M. Paulin
中科院分区：
文献类型：
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作者：
Vincent Forest;L. Barthe;M. Paulin
软阴影的精确生成是一项计算量特别大的任务。为了减少渲染时间，大多数实时和离线应用程序将阴影生成与光照计算解耦。除了这些近似方法外，它们仅在非常特殊的情况下使用一些限制性假设来生成阴影，这会导致半影高估或漏光伪影。在本文中，我们提出了一种算法，该算法能生成软阴影且不存在上述缺点。通过对两点之间遮挡物数量（即深度复杂度）进行一种新的高效评估，我们要么调制直接光照，要么对直接照明的渲染方程进行数值求解。我们的方法能近似半透明遮挡物投射的阴影，并能自然地处理具有空间变化亮度的面光源。此外，根据所需的性能和质量，生成的阴影要么非常接近光线追踪参考阴影，要么与光线追踪参考阴影一样精确。因此，所提出的方法非常适用于从对质量敏感的应用到对性能要求苛刻的应用等许多领域。
The accurate generation of soft shadows is a particularly computationally intensive task. In order to reduce rendering time, most real‐time and offline applications decorrelate the generation of shadows from the computation of lighting. In addition to such approximations, they generate shadows using some restrictive assumptions only correct in very specific cases, leading to penumbra over‐estimation or light‐leaking artifacts. In this paper we present an algorithm that produces soft shadows without exhibiting the previous drawbacks. Using a new efficient evaluation of the number of occluders between two points (i.e. the depth complexity) we either modulate direct lighting or numerically solve the rendering equation for direct illumination. Our approach approximates shadows cast by semi‐opaque occluders and naturally handles area lights with spatially varying luminance. Furthermore, depending on the desired performance and quality, the resulting shadows are either very close to, or as accurate as, a ray‐traced reference. As a result, the presented method is well suited to many domains, ranging from quality‐sensitive to performance‐critical applications.