Mirror flip using scale -1

Questions & Answers
1

When using scale -1 to flip an object, the colliders are not flipped correctly. Is there any other way to flip an object?

2

When flipping an object you're basically making the triangles go the other way around. I can never remember the order they're supposed to go but if they go clockwise normally, they would end up going counter-clockwise, effectively turning the mesh inside-out. A simple fix is to reverse the orders of the triangles so the mesh is turned inside-out to begin with.

using System;
using UnityEngine;

public class ReverseTriangles : MonoBehaviour
{
    public void Awake()
    {
        Mesh mesh = GetComponent<MeshCollider>().mesh;
        int[] triangles = mesh.triangles;
        Array.Reverse(triangles);
        mesh.triangles = triangles;
    }
}

Note however that this makes the mesh un-stripifiable, so if you plan on combining collider meshes you cannot make a triangle strip out of them.

Edit: I might have misunderstood "not being flipped correctly" as "being broken after being flipped". If they aren't being flipped at all, that's another story.

Edit 2: I also just realized I was assuming you meant a MeshCollider. If that's not the case, I don't have a solution for you other than to put the object in question inside a parent, and giving the parent the collider instead.

3

The colliders are flipped correctly when changing the scale in Unity to -1. If you're doing that in a modeling program, maybe it doesn't work; I'm not sure.

4

Your problem might be solved by:

GL.SetRevertBackfacing(true);

There are still major problems with lighting (only ambient and non-realtime light will work).