Nanite Tessellation pushes displacement in the wrong direction on landscapes with Z scale (UE-367789, still in 5.8)

General Issues and Bug Reporting (Unreal Engine)
1

Summary

Nanite Tessellation displaces in the wrong direction on landscapes with non-uniform Z scale (UE-367789). Still reproduces in UE 5.8 and 5.5.4. Flat ground is correct, but on slopes and cliffs the displacement is pushed almost vertically instead of along the surface normal, creating vertical streaks.

What Type of Bug are you experiencing?

World Creation Tools

Steps to Reproduce

  1. Create a new blank project in UE 5.8.
  2. Make sure tessellation is on.
  3. Create a new Landscape with default settings. Set its Scale to 100 / 100 / 1000.
  4. Sculpt a steep slope or cliff.
  5. Create a Landscape Material: plug a height texture into Displacement, enable Tessellation in the material’s Nanite settings. Assign it to the landscape.
  6. Enable Nanite on the landscape and click Build Data.
  7. Look at the steep slope up close.
  8. Repeat steps 3 to 7 with the Landscape Scale set to 100 / 100 / 100 and compare.

Expected Result

The displacement follows the surface normal of the scaled landscape, on slopes and cliffs as well as on flat ground, whatever the landscape Z scale.

Observed Result

At 100 / 100 / 1000, flat ground is correct, but on slopes and cliffs the displacement is pushed almost vertically. The relief slides along the cliff face and produces vertical streaks, worse as the slope gets steeper. At 100 / 100 / 100, the same material displaces correctly on the same kind of slope. The displacement seems to use the normal of the unscaled landscape, as described in UE-367789.

A Z scale different from X/Y is the standard way to import tall terrain from a 16-bit heightmap, so this makes Nanite Tessellation unusable on cliffs for any mountainous landscape.

Affects Versions

5.8
5.7
5.6
5.5

Platform(s)

Android

Upload an image

Terrain in 100.png
Terrain in 100.png1130×739 1.43 MB
Terrain in 1000.png
Terrain in 1000.png1224×750 1.34 MB

Additional Notes

Related to UE-367789, which lists 5.6, 5.7 and 5.7.4 with no target fix. I’ve confirmed it also affects 5.5.4 and 5.8.

Context: I sell landscape packs on Fab. My terrains are 8192 x 8192 m with about 3000 m of relief, imported at Scale 100 / 100 / 1000. There is no viable workaround on my side: lowering the Z scale flattens the mountains, a uniform scale forces a much coarser vertex spacing, and converting to a static mesh loses landscape collision. Nanite Tessellation on cliffs is therefore blocked until this is fixed.

Could you let me know whether a fix is planned, and in which version?