Why are the simplified mesh surface normals all flipped

I set the scene to a right-handed coordinate system, loaded the GLB model and simplified it, and the simplified result showed that all the surface normals were opposite to the original model, I have a few questions to ask:

  1. If a model with multiple meshes needs to be simplified, is there an easier way for me to simplify all its meshes?Now I’m using loops to deal with them one by one, which is a bit cumbersome.
  2. Why is there no problem loading this model in the scene, but the simplified model has the problem of normal flipping? Is it because I got the wrong setting somewhere?
    Thank you all.

hope for helps :smiling_face_with_tear:

The doc about mesh simplification is saying that artefacts with uv mapping can occur when using optimizeIndices. In that case, it suggests to use the optimizeMesh option instead.

Also, as meshes are coming from a .gltf/glb file, the mesh.overrideMaterialSideOrientation property should be copied over the simplified meshes.

Here’s a fixed PG:


Thanks for the help! Your reply is perfect and that PG seems like great.