Setting Light Cache to None on secondary engine slows rendering times

[msl]

Hi all,

I've used IR+LC for rendering for ages with prepass IR and a separate rendering pass with secondary engine set to none.

Now I've recently came upon a problem that with some scenes, setting the LC to None will absolutely destroy render times. A 15 minute frame on a single workstation might show render estimates of 15 hours. Same occurance repeats also on every workstation on our backburner farm with some scenes so it's not workstation related. If I put back Light Cache for the secondary engine on again, render times return to 15 minutes.

Does anyone know what might be causing this?

[RotemS]

Most likely you have 'store direct light' enabled in the LC.
If LC is not used, someone else needs to calculate direct light, and that is usually slower than the light cache.

[super gnu]

plus "use LC for glossy rays" is a massive timesaver..

why not just load the LC you calculated for rendering? it doesnt exactly consume many resources..