Hows does Daz3D decide whether to use CPU or GPU for iRay?
artphobe
Posts: 97
Hi all
Ive got 10 Genesis 8 characters standing next to each other (no clothing except a headpiece - hair might be too taxing). I have 16gb of RAM and a GTX 1080 Ti.
When I changed the resolution to 1440p, 4K GPU acceleration works.
Changing to 8K switches to CPU CUDA acceleration.
Hows does Daz3D decide whether to use CPU or GPU for iRay? Which factor affects this decision when changing the resolution of a render?
Post edited by artphobe on
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Daz 3d devs assume that you will be using GPU to render your Daz studio Iray render, so Iray is set as default
GPU is used if the whole scene data fit in the card's available VRAM. Otherwise CPU is used.
Memory.
Your scene should fit on the card, so this means geometry, all the textures, and the code iray needs to complete the computation.
If your characters are more than a few meters away, you can always half the textures, for instance with the product scene optimzer (or just with your image editor if you know how to work with surfaces and the textures directory)
I should add that it's not Daz Studio making the "decision" but Iray itself - unfortunately there isn't a reliable way to check before the data is passed to Iray.
That "reliable way" would be an awesome addition to Daz.
how do you know the size of your scene?
The way I do it is by checking the render log as it starts up. You know that little window that shows progress when you render? Open up the panel with the history button and it shows what memory is used for each iray config step.
You can try Iray Memory Assissant - it's not 100% precise, but it usually gives you a good idea about your scene.
When you run out of VRAM, Iray will drop to CPU rendering mode. There are lots of factors that drive up memory, including increasing the resolution as you have found.
It's not that hard, start the render, see if it switches to cpu rendering. If it does switch off and take out some stuff from the scene or load some lower res materials.
I also have Asus GPU Tweak to see at all times how much of my GPU memory is used. If it is in the 7.8 gb when the render starts (I have 8 gb 2070 super) there are some chances it will go over so I stop it and take out some more stuff.
Also using the computer while rendering could switch to CPU if you are at the limit. Opening one more youtube tab or a video player will take up some more of that memory.
Generally G8 characters textures tend to occupy a lot of memory but unless they are interacting with each other you can render your scene in stages and than put the renders together in Gimp or Photoshop.