Renderman's SubSurface procedure can be executed with knowledge of RSL, RiSpec, and an understanding of point clouds and brickmaps.
In previous write-ups point cloud generating bake passes were used to store occlusion data.
A similiar process is used with Subsurface Diffusion.
The objective is to create a SSDiffuse channel for the scene.
A point cloud containing radiance information is passed to the brickmake.exe to generate a radiance brickmap.
In the point occlusion write-up a shader was used to read baked occlusion data.
In this case, a shader that reads radiance data from a baked brickmap is needed.
Subsurface effects are dependent on lighting, therefore, the scene must have a lightsource.
Figure 01 is a surface shader for the preliminary bake pass. This shader instructs Rman to generate a point cloud with a radiance channel.
The resulting point cloud can be seen in Figure 02.
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Figure 02: Point Cloud with Radiance Channel
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