How many Light Cache passes should I use with DR?

[danb4026]

I have 2 machines, each with i7 2600K processors, so that's a total of 8 cores or 16 threads. Should I set the number of light cache passes to 16 or 8?

[matthewgriswold]

For a predictable result I would precalculate on just one machine, so 8. I've tried using DR with GI solutions in the past and things can get screwy.

[Bruce Hart]

I thought Light Cache was not distributed anyway? The number of passes would be the cores on your local machine - 8.

Someone can correct me here if this is wrong.

[matthewgriswold]

Dunno, I figured since light cache is a form of progressive path tracing it could be distributed across multiple machines. Whatever the case may be, you're probably better off calculating GI on one machine (saving the solutions to a network location) and distributing the frames to the network.

[Stephen Thomas]

Light Cache is not distributed, therefore you should calculate it on your fastest machine and set the number of passes equal to the number of cores you have on that machine.

[notamondayfan]

Yup light cache is calculated on each machine, and isn't shared with the other nodes.

 

If your machines are identical then I wouldn't bother pre-calculating the LC as in theory they should take the same amount of time to calculate the LC each, so there would be no advantage of pre-calculating, other than to possibly free up the 2nd node, but you would have to spend time doing the pre-pass, then realigning the LC, which can be time consuming.

 

I would only pre-calculate the LC if I have different nodes, with different processors, and only if the LC takes longer than 5 mins to calculate. I find pre-calculating is something that can save you a few mins rendering, but can cause all sorts of head aches if things go wrong.

[danb4026]

Thanks guys....understood.