Thoughts on making Cycles into a spectral renderer

[pembem22]

@Eary

A question though

the number of channels and data type will depend on the CMake configuration where spectral rendering will be enabled or disabled.

Does it mean the switching of spectral and RGB will be a CMake build option instead of the runtime check box? Is this switch going to be kept?

This patch only adds support for choosing spectral or RGB as a build option, but the CMake configuration is the same one used in previous builds where runtime switching was possible. The only difference is that you need two compiled kernels, instead of one, with spectral rendering enabled or disabled, which should be straightforward to implement with this patch. So it’s not a problem to add it in the future. The only concern I have is nearly doubling increasing by almost 30% the size of Blender installation.