Lightcache DR seems to be utilising 100% cpu on render node

[stevesideas]

Hi Guys,

Tell me if im wrong but I thought the lightcache could not be calculated via DR - only on the main computer. Why is it then that my render node is showing 100% usage whilst the lightcache is being calculated ?

Cheers


Ste

[vlado]

Each render node will calculate its own light cache solution, independently of the others.

Best regards,
Vlado

[stevesideas]

Ah I see. So once that has been done vray merges the lightcache information....I was wondering what it was merging

[voxel3d]

Hmm not exactly. As far as I know, each computer renders the LC totally independent of each other and the LC isn't shared / merged across nodes. The "merging" phase you see in the rendering dialog is when VRay merges all the different LC passes your computer rendered (which depends on how many CPU cores you're running on unless you've manually set it to calc the LC in "x" passes).

So in a nutshell, the LC calculation isn't shared at all between DR nodes, the calculation each node does duplicates what the other ones do.

Jorge

[stevesideas]

Oh ok. So, a seperate lightcache is calculated per core ? So say I habe a quad core machine does that mean I should set the lightcache passes to 4, or should I set it to 12 because there are 12 cores being used to render the scene (my quad core & my dual xeon 5355 = 12cores)??

[voxel3d]

In this case I think you would set it to 8, since that's the most cores rendering the scene (the dual qc xeon). I think 8 is the default in SP2 anyways. This setting is per-node, so you should set it to the highest number of cores any single node that is participating in the DR has.

You can set it lower but then nodes that have more cores than the passes you set it to will under-utilize their resources. Like-wise, you can set it higher than needed but from what I remember Vlado saying, all things being equal a LC with a higher number of passes will be slightly lower quality than one computed using less passes. From what you're saying about your hardware, just keep it at 8 and you'll be fine.

Jorge

[stevesideas]

Thanks for the info Will give that a go..