lightcache passes

[glorybound]

What does the lightcache passes actually do? I built a little render farm with 5 - i7 with 12 Gb DDR3 per box. I rendered a scene with the default 8 passes and it took 28 minutes. I rendered the scene using vray dr and the default 8 passes and it took 5 minutes (sweet) and then I rendered the same scene with vray dr and 24 passes and it took 6 minutes 30 seconds.

[plastic_]

lightcache passes = threads.
if you got 8 cores you have to use 8 threads, otherwise some cores will idle.

using more passes will reduce quality though. it's like blending multiple PPT images together...

[glorybound]

cores

So if I have 44 cores do I put 44 cores for my passes? The vray help says put 1 for best results. The more cores the slower it goes and the quality denigrates so I am not seeing the benefit of more cores for lightcache passes.

[plastic_]

sorry, I should have been more precise...I meant CPU cores of single computers, not all together...
with the core i7 and hyperthreading you should use 8 lightcache passes, in order to keep the CPU busy...
with render farms you should use the max number of cores that is used by any computer in the farm.
so sticking with 8 is fine, unless you got extreme hardware with even more cores in your farm.

the reason why vray is not using all cores by default is because the output may be different between frames (flickering), when the number of passes differ.

if you're only rendering on a dual core notebook for example, then you can reduce the LC passes to 2.

that's how I understand it.

[glorybound]

lc

gotcha... so 8 cores, the default, is what I'll stick with