Are the cache and photon settings totally independent? Can I get a photon solution then try completely different cache settings--like switching between auto-occlusion and retrace--without having to redo the photons?
Yes, you can save the photon solution using the photon map files section at the bottom of the detailed photon controls. If 'load' is checked in the photon map file settings, the last saved file will be used as the solution. If you leave it on 'save', the solution will overwrite the file. The irradiance map cache works in the same way and is independent of the photon map file.
Thanks I knew you could do that, just not 100% positive the two were 100% independent.
Is there something that leads you to believe they aren't separate? To my knowledge they are... but if there's a special case where this doesn't hold true, please let us know.