The SGGX microflake distribution
The SGGX microflake distribution
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DOI：
10.1145/2766988
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发表时间：
2015-07
期刊：
影响因子：
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通讯作者：
E. Heitz;J. Dupuy;C. Crassin;C. Dachsbacher
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文献类型：
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作者：
E. Heitz;J. Dupuy;C. Crassin;C. Dachsbacher
我们引入对称GGX （SGGX）分布来表示各向异性微片参与介质的空间变化性质。我们的关键理论见解是通过微片的投影面积来表示微片分布。我们使用投影面积来参数化椭球体的形状，从中我们恢复了一个正态分布。基于投影面积的表示允许鲁棒线性插值和预滤波，并且由于其几何解释，我们推导出microflake框架中使用的所有操作的封闭形式表达式。我们还在我们的理论框架中纳入了具有漫反射的微片。这允许我们对粗糙的漫射材质和粗糙的镜面材质进行建模。最后，我们利用对可见法线分布进行采样的思想，为我们的SGGX微片相函数设计了一个完美的重要采样技术。它是分析性的、确定性的、易于实现的，并且比以前的工作快一个数量级。
We introduce the Symmetric GGX (SGGX) distribution to represent spatially-varying properties of anisotropic microflake participating media. Our key theoretical insight is to represent a microflake distribution by the projected area of the microflakes. We use the projected area to parameterize the shape of an ellipsoid, from which we recover a distribution of normals. The representation based on the projected area allows for robust linear interpolation and prefiltering, and thanks to its geometric interpretation, we derive closed form expressions for all operations used in the microflake framework. We also incorporate microflakes with diffuse reflectance in our theoretical framework. This allows us to model the appearance of rough diffuse materials in addition to rough specular materials. Finally, we use the idea of sampling the distribution of visible normals to design a perfect importance sampling technique for our SGGX microflake phase functions. It is analytic, deterministic, simple to implement, and one order of magnitude faster than previous work.