The dreaded black buckets

[bigbossfr]

Thanks.

My main machine is 24 (hyperthreaded) cores. The other two machines are 16 cores. Should my light cache passes be 24 , 56, or 0? Currently 24 is causing no flickering, but is quite slow.

Yes, because you have 24 LC passes on all computers.
But if you set 0, you will have differentes number of LC passes, and, it is a problem for animation ?

[Bertjenkins]

I thought the light cache passes number referred to the host machine, or single machine with the greates number of cores?
So are these flicker problems occuring when vray tries to send out light cache jobs to other machines?
I'll stick to my 24 setting, but it would be nice to use all 56 cores.

[tashko.zashev]

I thought the light cache passes number referred to the host machine, or single machine with the greates number of cores?

Exactly, to avoid any differences in the light cache map, the "number of passes" value should be set to the number equal to the number of CPU threads. When all render nodes has different number of threads, this parameter has to be set with the greatest value.
In theory zero will produce flickering in case that some render nodes has different cores, but i haven't test it.

So are these flicker problems occuring when vray tries to send out light cache jobs to other machines?

One method is to precalculate the LC map on the fastest machine and reuse it later at the render stage, and second/regular one is to let every machine to calculate it. Both approaches will work for DR or backburner.