PCG-generated ISM meshes render without materials on nDisplay render engines — nDisplay plugin disabled (Reality Hub / Zero Density setup)

Development Cinematics & Media Virtual Production
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1

Hi everyone,

I’m running into an issue that is specific to a virtual production setup using Zero Density Reality Hub as the cluster solution — not a standard nDisplay setup. I’m posting here because the root cause likely sits in UE, but the symptom only appears on the render engines, not in the editor.

Setup:

  • Unreal Engine 5.7
  • Zero Density Reality Hub (own cluster solution, replaces nDisplay)
  • 4 render engines loaded via Reality Hub
  • PCG Graph: Get Actor Data (by Tag) → Surface Sampler → Static Mesh Spawner
  • 4 mesh entries using Fab vegetation assets, all present in the project Content folder
  • PCGWorldActor present in the level
  • Generation Trigger: Generate on Load
  • Evaluate World Position Offset: enabled on all mesh entries
  • Nanite: disabled on all affected meshes
  • nDisplay plugin: disabled in .uproject (was necessary to resolve a DisplayClusterGameEngine crash after migrating from UE 5.5 to 5.7)

Problem:
In the UE 5.7 editor on the workstation, all PCG-generated meshes display correctly — full materials, textures, alpha transparency and WPO wind animation. When the level is loaded via Reality Hub on the render engines, all PCG-generated meshes appear as untextured silhouettes with no alpha transparency and no WPO animation. The geometry is present and correctly placed. All non-PCG assets in the same level render correctly on the render engines.

Already tried:

  • Forcing hard references to all 8 used materials via a Blueprint actor placed in the level → no effect
  • Generation Trigger set to Generate at Runtime → meshes disappear completely, even in editor PIE
  • Rebuilt the entire PCG setup using the new PCG Landscape Mode in UE 5.7 → same result

Current hypothesis:
The PCGWorldActor relies on nDisplay for cluster synchronization of PCG component data. With nDisplay disabled and replaced by Reality Hub’s own cluster solution, this synchronization may be broken — Reality Hub correctly syncs the geometry, but the material assignment of the ISM instances is lost in the process.

Before testing the obvious fix (re-enabling nDisplay), I wanted to ask: is PCGWorldActor fundamentally dependent on nDisplay for correct ISM material assignment in a cluster context? And are there known issues or workarounds for running PCG in a non-nDisplay cluster environment?

Thanks in advance.

Michael

2

After digging deeper with log analysis, here is what we found:

The render engine logs showed:

LogMaterial: Warning: Material [MI_name] missing 
bUsedWithInstancedStaticMeshes=True! Default Material will be used in game.

The flag was missing on some Fab standard parent materials. After setting bUsedWithInstancedStaticMeshes=True on all relevant parent materials and clearing the Zen DDC cache on the render engines, the warning is gone from the logs.

However, the visual problem persists. PCG-generated meshes still appear as untextured silhouettes despite no material warnings remaining in the log.

This suggests the ISM flag was a contributing factor but not the root cause. The deeper issue seems to be elsewhere — possibly in how PCG-generated ISM instances handle shader permutations at runtime in this specific environment (Zero Density Reality Hub, nDisplay enabled but no nDisplay config actor in the level).

Has anyone seen PCG-generated ISMs render without materials despite the ISM flag being correctly set on all parent materials?