Why is Iray not using my GPU?

Morokei

According to Task Manager, Daz Studio only uses my CPU while rendering. Zero GPU usage. I let a render run for over an hour and this never changed. Sometimes CPU usage got up to 100%, but GPU never went above 0%.

In the Render Settings > Advanced > Hardware, I have:

• GPU checked and CPU unchecked (in both Photoreal and Interactive(Biased))
• In Scheduling
  • CPU Load Limit: 6
  • CPU Thread Affinity: unchecked
• Allow CPU Fallback unchecked
• Allow GPU Detection checked
• Check GPU Driver Version checked

Aren't these settings supposed to keep it all on the GPU?

Are my settings wrong? Is that CPU Load Limit Is Task Manager wrong? I'm so confused.

• DS Version 4.20.0.2
• Windows 10
• NVIDIA GeForce GTX 1660 Ti

feldarzt

The last time I had this issue, I had a GPU with a VRAM amount not enough to handle the scene.

Is your scene too heavy for your GPU?
What do you have there? How many G8 or G9 characters?

PerttiA

Task Manager is not a good tool for checking, unless one knows how to set it up and how to read the results.

GPU-Z is a lot better.

Richard Haseltine

In task Manager check the performance tab, select the GPU, and set one of the graphs to CUDA (if there - if not try Compute 0).

TimberWolf

Your GPU is definitely doing the render, despite what Windows tells you (see above for how to get a clearer picture). As you've unchecked 'fallback to CPU' your renders would just be an almost instant black screen if you exceeded the available VRAM on your card. If you want to be sure, the Windows report of the GPU's temperature is pretty accurate - it won't be idling. The fact that you haven't exceeded your card's VRAM surprises me a little bit as 6GB really isn't enough these days. RTX emulation (for non-RTX cards, obviously!) takes up about 2GB, although I believe you can still disable this memory useage by setting 'Ray Tracing Low Memory' to On in Render Settings -> Optimization at the cost of speed but I haven't ever used this or checked it. Windows will easily hack off another 0.5GB, iRay will also reserve some workspace depending on the resolution of your render which doesn't leave you very much for your scenes.

Windows 10/11 has some components which will happily run your CPU at 100% unless they get an interrupt. The easiest way to do this is to start Task Manager and then minimise it. It's a quick and dirty hack but it works, the alternative being messing about with the .NET framework which I'd hesitate to recommend.

If you can, have a think about adding an RTX card to your PC - an addition of something like an RTX 3060 as a standalone card whilst you used your 1660Ti to drive the monitors would make a massive difference to your setup. 32GB of system RAM to run this comfortably. There are better cards than the 3060 some of which I think, even though they're more expensive, are actually better value but it's currently the cheapest way to drag your PC to a spec. which is comfortable for rendering.