Iray question regarding Advanced Render Settings

Petra

What do I check when rendering with Iray

There is Photoreal Devices and Interactive Devices and in both you can check GPU or CPU and there is also Optix Prime Acceleration.

Do I check the GPU in both Photoreal Devices and Interactive Devices or only in on of them?

Do I also need to check CPU for Iray rendering or does it not much of a dfference in terms of Render times?

Thank you :)

marble

I'm a complete IRay newbie but I have already noticed that turning on Optix Prime results in considerably more VRAM being used by the GPU. My 4GB GTX970 is already approaching VRAM limits on many scenes so I switched off Optix Prime. I can't say that I noticed a performance hit by switching it off.

I don't have CPU checked either. I'd rather know that the scene won't fit than be fooled into thinking it is using my expensive GPU when it is actually crawling along in CPU mode. I'd also like to know whether this is the wrong decision though - how much difference to render times does it make to have both checked? I've read some very conflicting opinions.

Other than that, I hope others will answer the rest of your questions.

thd777

Regarding CPU plus GPU:

In my experience there is not much of a point to have the CPU checked if you use a decent GPU (I use one GTX980 and one GTX780ti). In my tests the CPU only contributed between 2 and 5% of the total number of iterations done at the cost of a less responsive system. Since then I am running GPU only as long as the scene fits into the GPU memory.

Ciao

'TD

Petra

Thank you for the quick reply, it has helped me a lot :)