assimp/assimp

Bug: GLTF/GLB importer reads abnormal skin weights.

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#6,130 opened on May 4, 2025

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 (5 comments) (0 reactions) (0 assignees)C++ (2,795 forks)batch import
BonesBugPlatform UnrealglTF2.0help wanted

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Description

Describe the bug For certain GLB/GLTF files exported from Unreal Engine, O3DE (uses assimp 5.4.3) renderes incorrect skin mesh. Running assimp dump shows that some of the skin weights are abnormally large. However, the asset is correctly imported by Godot or Unreal.

To Reproduce Steps to reproduce the behavior:

  1. Go to Unreal Engine
  2. Export a character model file (e.g. Paragon Shinbi)
  3. Import it on O3DE or assimp dump

Expected behavior The skinned mesh is expected to be rendered without holes.

Screenshots

Image

Image

Platform (please complete the following information):

  • OS: Windows
  • Browser Chrome
  • Version 5.4.3

Additional context N/A

Contributor guide

Research direction
Investigate the GLTF/GLB importer in assimp (likely in code/AssetLib/glTF/). Focus on how skin weights are parsed and normalized. Compare with Godot/Unreal's handling. Look for any truncation or scaling issues in the accessor data.
Tech stack
None
Domain
None
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitC++3D graphics basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55