This behavior appears to be a regression new to UE5, as I tested in 4.25 and the issue does not occur.

Interestingly, the issue clears up if you switch to No, FXAA, or MSAA antialiasing methods. The issue appears to only occur with TSR and TAA.

The issue does not seem to occur if you switch the PPM to BeforeTonemapping (although then the world position values get tonemapped which may be undesirable).

Steps to Reproduce
  1. Create a new, blank map.
  2. Add to the map a simple plane, and set its scale to 500,500,500.
  3. Create a new material called PPM_WorldPosition. Set it to the PostProcess domain, and set up a simple network of frac(WorldPosition / 1000.0).
  4. Add to the map a postprocess volume with infinite extents and using the postprocess material you created.
  5. Fly your camera around the map, and observe bands of blue leading into black changing location as you move throughout the world.

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CreatedSep 20, 2022
ResolvedSep 21, 2022
UpdatedJun 8, 2023