Black blotches on some meshes in MRQ at higher resolutions and through gaps

Development Rendering
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1

Hi, I’ve been struggling for ages with this issue. Some meshes have these black marks on.

Distance doesn’t seem to matter - it happens near and far.

However - rendering tiled GUARANTEES this will happen on certain meshes - and all foliage

Here you can see it on a rock and some trees. And you can also see it around the leaves on the rock photo.

(note these images are colour managed which is why they are slightly washed out for us)

blotch2
blotch21021×1354 469 KB

blotch1
blotch1820×592 214 KB

They also appear if you look through small gaps, like the camera going past leaves:

image
image752×901 127 KB

I OCCASSIONALYL see them in viewport - but they fade away. I do not appear to be able to see them in any debug view.

I have tried in projects with only default settings, I have tried with different materials. It still appears on scaled meshes. I do not have distant fields on, but I have tried it with.

I am using VSMs and my directional light is NOT pathtraced.

Thank you

2

Hello there @Knoopmas!

Checking through the community, this is a recurring scenario, with multiple causes. Let’s cover a few possible resolutions:

  • As a first step, to rule out pre-existing elements on your system, please update your OS to the latest version, and update your video drivers to the Developer version (pick the “Clean Install” option if available)

  • Disable MRQ tiling, as its combination with VSM is a usual suspect for causing artifacts.

  • Disable Virtual Shadow Maps entirely, and test with traditional shadows or ray traced shadows instead

  • Force your foliage to fixed LOD, preventing LOD transitions during render

  • If you are using Nanite, test disabling it, as it may cause strange shadow effects on render

3
  1. updated and latest drivers
  2. It does not happen with tiling, or lower resolutions - but I really need to render at these higher resolutions
  3. VSMs - doesn’t seem to happen with normal SMs but messes up other stuff in such a high poly scene
  4. it happens with foliage items and without
  5. Nanite turned off seems to fix it! But I then have LOD loading problems with such a dense scene.

Based on this I think it is something to do with the breaking down of meshes to their lower LODs with nanite, but somehow tied to resolution.

edit to add: it seems like perhaps screen traces make a difference