I am trying to understand memory usage whilst rendering in Cycles with a view to making good upgrade option decisions.

I have a large scene which for my system is very heavy to render. I have 32 Gb of RAM but have had to increase the swap file to 90 GB (yes 90Gb!) in order to fit the scene in without crashing Blender. And that's after optimisations and turning off everything I don't absolutely need. Compositing is not really an option (it partially is) - but for the purposes of this question it isn't relevant anyway.

So my system is using 82 Gbs of RAM to render the scene, but the render screen shows a peak of just over 14 Gbs of Memory, whilst the scene information in the lower right hand corner is showing memory of around 48 Gbs, VRAM 1.4/6.0 Gb (that would be the viewport).

What do they refer to? The render pane is showing a peak of 14.5 Gb of Memory, bottom right hand corner 48 Gbs, and the system 82 Gbs.

  • The system using 82 Gbs; that is surely all the objects assets and textures loaded and ready to be accessed.
  • 48 Gbs, is that what is currently being accessed in order to render the scene?
  • 14.5 Gbs peak, is that the memory required to render the scene (lighting, samples, etc)?

If I upgraded and dual-linked GPUs via NVlink, so I had a pool of 16 Gbs for GPU rendering, would I be able to render via GPU? My biggest bottleneck to achieve what I am looking to do in blender is render times/VRAM. RTX 2060 Supers NVlinked on optix would give me 16 Gb VRAM and really good rendering performance for a reasonable price. It means I could prioritise fast processors instead of multiple cores.

Can anyone help with this?


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