R.Design
TroubleshootingRendering IssuesObject Distortion (Nanite)

Object Shape Distortion in Rendering (Nanite Fallback)

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This article explains the issue where specific furniture or objects appear distorted, blocky, or jagged like triangles when rendering with Path Tracing.

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Keywords for Symptom Identification

Users may report this issue using expressions such as:

  • “The shape in the rendered image looks weird”
  • “Objects look blocky / low-poly / jagged”
  • “Pointy triangles / distorted shapes”
  • “Looks fine in preview (viewport) but dirty/broken in export”
  • “Mesh is collapsed/broken”
  • “Lights or shelves are deformed”

Symptom

Objects that appear normal in the editor viewport or real-time preview appear with distorted shapes only in the resulting image from High-Quality Rendering (Path Tracing).

Example of shape distortion due to Nanite fallback

Areas indicated by red arrows: Lighting fixtures and shelves appear with rough, distorted shapes

Typical symptoms:

  • Smooth curved surfaces look like a collection of rough triangles (polygons)
  • Parts of the object stick out sharply
  • The object seems to be replaced by a simplified shape different from the original

Cause: Nanite Fallback Mesh

The primary cause of this issue is the “Fallback Mesh” setting in Unreal Engine 5’s Nanite feature.

  1. How Nanite Works: Nanite automatically adjusts mesh detail based on camera distance. However, during Path Tracing (Ray Tracing) calculations, it may reference a “Fallback Mesh” (proxy mesh) to save computational cost instead of the full Nanite mesh.
  2. Insufficient Setting: If the resolution (polygon count) of this fallback mesh is set too low, that rough shape is rendered directly in the final image.

Solution

This issue requires a fix by the content creator (3D modeler/engineer). Users cannot fix this themselves, but please gather the following information to isolate the issue.

Questions for Users

  • Does the issue occur in “Path Tracing (High Quality)” mode?
  • Does it look normal in Real-time Preview (Lumen)?
  • Does it occur only with specific items? (Identify the item name)

Fix Procedure for Dev/Production Team

Modify the Static Mesh settings for the problematic item using one of the following methods.

Method A: Increase Fallback Precision (Recommended)

Improve the mesh precision for path tracing while keeping Nanite enabled.

  1. Open the Static Mesh Editor for the asset
  2. Locate the Nanite Settings panel
  3. Set the Fallback Triangle Percent value to 100% (or a similarly high value)
  4. Click Apply Changes to rebuild the mesh

Method B: Disable Nanite

Turn off Nanite for simple shapes or if Method A does not resolve the issue.

  1. Open the Static Mesh Editor
  2. Uncheck Enable Nanite Support in Nanite Settings
  3. Click Apply Changes

Related Information

Visual Quality Issues