I have been facing this render problem recently where when I switch on CPU and CPU fallback it just takes on forever and ever after 30 minutes its 0 percent rendered and the quality of that when I cancelled the render was super grainy but when I switch these settings of the render gets over in 10 seconds but the iray preview is black and white and the final render is just a pitch black screen.
I am using a 3070 laptop , maybe I am not allowing all my Gpu to be utilised for Daz 3d not sure but this problem makes it almost impossibe for me to render.
This is because your scene has exceeded your GPU's VRAM.
It is not rendering on the GPU
at all.
When you have CPU fallback turned
on, when it fails to load to the GPU it will switch to rendering the scene on the
CPU only, and is an order of magnitude slower than GPU rendering.
When you have CPU fallback turned
off, when it fails to load to the GPU
you get a black screen and it ends the rendering attempt.
You need to optimize your scene to fit on 8GB VRAM. This means hiding objects that are out of sight, reducing texture sizes, splitting the contents of the render into multiple renders that are spliced together in post, checking for rogue emissives, etc etc etc. There are lots of different ways to reduce your scene's VRAM footprint. It's a pain in the ass, but that's just the way of it when you're rendering with 8GB VRAM.
Disable CPU rendering entirely so you know when a scene fails to fit on VRAM. This will be your indication to optimize the scene.
I mentioned all of this the last time you asked about CPU/GPU rendering.
Also, don't forget to restart Daz frequently, to prevent memory leaks from failing/slowing your renders. You should ideally render once per Daz session, exit, and load it up again for the next render. You can use Render Queue to automate this process.
