Unexpected results from Raycast.GetCollisionFaceIndex on Concave Mesh

[peteski]

Tested versions

• Reproducible in Godot Engine v4.4.1 mono

System information

MacOS 15.5

Issue description

When using Raycast.GetCollisionFaceIndex in conjunction with the MeshDataTool's meshDataTool.GetFaceVertex, the resulting points are sometimes from a different face.

In some cases it works fine (as in 1 and 3), could this be to do with the way Godot creates concave collision meshes internally? I'm not sure where the problem is coming from but there seems to be some difference between the face index from the raycast and the face index from the meshdatatool.

Steps to reproduce

Here is the basic script I've been using in my tests, I've also included a simplified project demonstrating the issue.

    public override void _PhysicsProcess(double delta)
    {
        base._PhysicsProcess(delta);
        
        // Move raycast point
        float time = Time.GetTicksMsec();
        float offset = Mathf.Sin((time) / (1000) );
        raycast.Position = new Vector3(offset * 4, raycast.Position.Y, 0);
        
        // Update collision data
        if (raycast.IsColliding())
        {
            CollisionObject3D other = (CollisionObject3D)raycast.GetCollider();
            meshInstance3D = other.GetParent().GetNode<MeshInstance3D>("Mesh");
            meshDataTool.CreateFromSurface((ArrayMesh)meshInstance3D.Mesh, 0);
            
            // Highlight points that make up the collision face
            int collisionFaceIndex = raycast.GetCollisionFaceIndex();
            for (var i = 0; i < 3; i++)
            {
                var index = meshDataTool.GetFaceVertex(collisionFaceIndex, i);
                var vertex = meshInstance3D.ToGlobal(meshDataTool.GetVertex(index));
                debugSpheres[i].GlobalPosition = vertex;
            }
        }
    }

Minimal reproduction project (MRP)

Example Project.zip