Summary
When importing Mixamo characters into Unreal Engine 5.8, the automatically generated Physics Asset creates incorrect collision capsules for the LeftFoot and RightFoot bones. The generated capsules are significantly larger and improperly aligned compared to the actual foot geometry. As a result, the collision shapes penetrate the floor plane and cause the character to remain offset above the ground, producing a visible floating effect.
The issue appears reproducible across multiple Mixamo characters and does not occur when importing the same FBX files in Unreal Engine 5.7. This behavior suggests a regression in the Physics Asset generation process introduced in Unreal Engine 5.8.
Reproduction Rate: 100% with tested Mixamo character assets.
What Type of Bug are you experiencing?
Animation
Steps to Reproduce
- Open Unreal Engine 5.8.
- Create a new Third Person project.
- Import a character downloaded directly from Mixamo using default import settings.
- Allow Unreal Engine to automatically generate a Physics Asset.
- Open the generated Physics Asset.
- Inspect the collision capsules assigned to LeftFoot and RightFoot.
- Place the character in the level and observe its position relative to the floor.
Expected Result
The automatically generated Physics Asset should create collision capsules accurately fitted to the foot geometry. The character should stand naturally on the floor without any vertical offset.
Observed Result
The automatically generated Physics Asset should create collision capsules accurately fitted to the foot geometry. The character should stand naturally on the floor without any vertical offset.
Affects Versions
5.8
Platform(s)
Windows
Upload an image
Additional Notes
Additional Observation and Temporary Workaround
During investigation, it was determined that the issue is directly related to the automatically generated collision capsules assigned to the LeftFoot and RightFoot bones in the Physics Asset.
As a temporary workaround, manually editing the generated foot capsules resolves the floating behavior completely.
The following adjustments were applied:
LeftFoot Collision Capsule
• Rotation: approximately -51°
• Radius: 9.6
• Length: 17.4
RightFoot Collision Capsule
• Rotation: approximately -51°
• Radius: 9.6
• Length: 17.34
After saving the modified Physics Asset and Skeletal Mesh assets, the character correctly contacts the floor and no longer exhibits floating behavior.
This workaround suggests that the root cause is likely related to incorrect capsule sizing and orientation during the automatic Physics Asset generation process in Unreal Engine 5.8.
Because the same FBX asset generates properly sized foot collision capsules in Unreal Engine 5.7, this behavior appears to be a regression introduced in Unreal Engine 5.8.