Path Tracing Render Crashes on Large Project (RTX 4080 Super, 64GB RAM)

Development Rendering
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1

Issue Description:
I’m working on a very large Unreal Engine project — a compound with around 1000 villas. The project also contains heavy foliage, and since I need to render many sky shots, I’m not using LODs (I want all distant details to remain visible).

The problem is that when I attempt to render using Path Tracing, Unreal Engine keeps crashing. Before the crash, I checked performance and noticed that both GPU memory and system RAM are maxed out.

System Specs:

  • GPU: RTX 4080 Super (16GB VRAM)

  • RAM: 64GB

  • Renderer: Path Tracing

Question:
Is there any way to render this project successfully without crashing, even if it takes much longer to render (I don’t mind long render times), or is this simply beyond the capability of my hardware setup?

I’m mainly looking for workflow tips or settings that would let me render the project at full quality without reducing mesh/foliage details.

2

Its certainly possible you are just asking too much of your card. Is texture streaming disabled? I would maybe start there. When you are rendering in MRQ you can hit the tilda key to bring up a command line in the render window which you can then use to ProfileGPU.

3

I understand.

What would be the most effective approach to optimize a very large project like mine? My end goal is to produce a high-quality cinematic bird’s-eye render of the entire project, but at the moment I’m facing performance issues and feeling a bit stuck on how to proceed efficiently.

4

Flip in Pathtracer in the viewport and run stat memory. That should provide a starting point.

5

Are you using Movie Render Queue?

If so, you could try some of the following:

  • Use tiled rendering. This will subdivide the render into several smaller ones which are then stitched together.
  • Different Anti-Aliasing settings consume different amounts of VRAM. I have been successful in the past by changing them.
  • You might want to keep Texture Streaming enabled. This would reduce VRAM cost but some textures might appear blurry
6

Tiled rendering and the different AA methods are not applicable to PT. Texture streaming is good advice though :slightly_smiling_face:

7

I see.

Is there a reliable method to implement this in my existing project, which is already complete and not using virtual textures? I’ve encountered several issues when attempting to convert standard textures to virtual textures.

8

Look under Game Overrides in MRQ/MRG. Make sure that is not shutting off streaming.

9

Thanks Shaun for correcting me. I did not think about the MRQ differences between Lumen and PT.

More ideas:

You could reduce Pathtracer bounces in your Post Process Volume (or camera). It defaults to 32 but for an exterior scene as low as 2 or 3 could be enough. I am not sure if and how much it affects VRAM, but might be worth a try. Please make sure the Post Process Volume is set to infinite extent.

In Project Settings → Movie Pipeline New Process you can tick “Close Editor”. If you select Render Remote in Movie Render Queue the Editor will close and only run the rendering. This could also save some memory.

Is upscaling an option for you? If so, the Nvidia DLSS plugin also offered MRQ support. I do not know if this is still the case or compatible with PathTracer.