IrradianceCache

From Odwiki

Irradiance Caches in Mantra

The Irradiance Cache is a file or data in RAM that can be written out and/or read in during Irradiance or AmbientOcclusion to increase the speed of repetitive rendering, and also to provide better filtering on the samples to counteract noise. By default irradiance caches are stored in memory but you can add RenderingParameters called "Irradiance Cache File" (vm_gifile) and "Read/Write Mode" (vm_gifilemode) to cause these to be written to disk and re-used.

All the samples sent out by the irradiance() or occlusion() VEX functions can be stored in one of these files.

The tool i3dconvert (one of the CommandlineTools) allows the user to convert the Irradiance Cache to a point cloud as a bgeo file, which may be read into Houdini using a FileSOP. This is useful and interesting to see where the samples are landing during the global illumination process.

Another technique for re-using computations are available with VexPointClouds.