Unreal Engine 5.8 texture brush + lightning bug > terrain gets dark

[9ztutuquitaa]

Summary

Painting Target Layers (Grass/Dirt/Rock/Gravel) on a Landscape works
correctly after proper setup, but running Build Lighting (which
internally runs Build Reflection Captures) causes the entire
landscape to render solid black. Repainting any layer immediately
restores the correct appearance. Root cause: the GPU-cached Edit Layers
weightmap merge result gets flushed by the reflection capture build step
and is never automatically re-triggered.

What Type of Bug are you experiencing?

Rendering (Graphics / Niagara)

Steps to Reproduce

Steps to Reproduce

1. Create a new Landscape and assign a Landscape Material using a
   LandscapeLayerBlend node with LB_WeightBlend layers (Grass, Dirt,
   Rock, Gravel).
2. Create Target Layer Info assets for each layer, set
   BlendMethod = PremultipliedAlphaBlending (Advanced Weight
   Blending, required for Edit Layers compatibility).
3. In Landscape Mode → Paint, paint any layer (e.g. Grass) across the
   terrain. Confirm the texture renders correctly.
4. Open the level menu and run Build → Build Lighting Only (or
   Build All), which triggers Build Reflection Captures as a
   sub-step. This step has real work to do because the level contains a
   leftover SphereReflectionCapture actor from the template map.
5. Observe the landscape after the build completes.
6. Select the Paint tool again and re-paint any layer.

Expected Result

The landscape keeps showing the painted textures before, during, and
after any Build operation. Build Reflection Captures should not affect
already-painted Target Layer data, since Lumen (enabled, light is
Movable) does not require baked reflection captures at all.

Observed Result

Step 5: the entire landscape renders solid black, as if every
Target Layer weight were 0. No error is logged. The Target Layers list,
Layer Info assets, and Edit Layer (visible, unlocked, weightmap alpha
1.0) all remain in a valid, correctly-configured state — verified via
script (ObjectTools.get_properties, list_target_layers,
describe_edit_layers). No shader or material compile errors appear
in the log.

• Step 6: painting any layer again immediately restores full correct
  rendering, with no other change needed.

Affects Versions

5.8

Platform(s)

Windows

Upload an image