Dark shading appears on mesh when setting up physic bodies

Development Asset Creation
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1

I’m just testing out what will eventually be net physics for my soccer goal posts. I’ve set up some physics bodies and applied some constraints and the effect isn’t too bad. However; what is this dark shading that appears towards the end of the simulation?

2

Hey there!

I think this might be related to how the mesh normals are updating during bone deformation/physics movement or possibly shadowing/ambient occlusion artifacts caused by overlapping physics bodies or geometry stretching

To help narrow this down and figure out what’s going on, Could you share a few extra details?

  1. Unreal Engine Version
    Which version of UE are you using (e.g, 5.3, 5.4)?

  2. Material Setup
    Is the material assigned to this mesh using standard Lit mode or do you have skinning/dynamic normals settings enabled?

  3. Physics Asset Setup
    Are the physics bodies intersecting significantly when the constraints pull them together?

In the meantime a couple of quick things I’d try checking:

  • Recompute Normals/Tangents
    If this is a Skeletal Mesh make sure Recompute Tangents is checked in the Material options or Mesh settings to see if it fixes the shading stretch during deformation.

  • Self-Shadowing/Contact Shadowing
    Try temporarily setting the mesh Cast Shadow to “False” or testing with a simple Unlit/Flat material.
    If the dark shading disappears, it’s a lighting/shadowing calculation issue rather than a vertex normal distortion

Epic Documentation: Physics Asset Editor

Let me know what you find with those checks

3

Hey. Thanks for reply. I will go away and try these suggestions and get back to you.
It’s UE 5.6 btw and I’m just using the default WorldGridMaterial.

4

Awesome, thanks for clarifying that. Knowing you’re on UE 5.6 and using the default WorldGridMaterial helps narrow things down quite a bit

Because WorldGridMaterial uses World Position Offset + procedural triplanar/world aligned mapping for its gridding effect, if you apply a lot of deformation or movement to bones during the physics simulation the UV projection/normal vectors can be distorted causing unexpected shading and ambient occlusion effects.

Here are a couple of target steps to check while testing

  1. Test with a Basic Solid Material
    Try assigning a basic, flat, non-procedural material (just a simple Constant 3 Vector connected to Base Color in a standard Lit material) instead of WorldGridMaterial.
    If the dark shading disappears, the issue is purely how WorldGridMaterial projects its UV grid under dynamic physics deformation

  2. Check Mesh Skin Weights & Skeleton Normals
    If this is a Skeletal Mesh undergoing severe deformation from physics bodies, ensure your skin weights transition smoothly between the bones. Extreme stretching without enough geometry or smooth weights can invert/distort vertex normals, making lighting and self-shadowing look dark or glitchy.

  3. Physics Body Capsule/Sphere Overlap
    In your Physics Asset, double-check if adjacent physics bodies (colliders) are overlapping heavily at the end of the simulation.
    If they press tightly together, self-shadowing/Lumen ambient occlusion might trigger that dark shading where the geometry pinches

Take your time testing those out and let me know how it goes once you get a chance to check!