Highlight Cube Face

I was looking around yesterday for a script that would allow me to highlight a cube face similar to the way Cheetah3D does. To my surprise, it has been asked about quite a bit on the forums, but I couldn't find any working code. So after a couple hours of research (as I know nothing about meshes), I managed to figure it out.

Code (csharp):

1.  
2. var highlightColor : Color;
3. private var lastMesh : Mesh;
4. private var lastHitNormal : Vector3;
5.  
6. function Update () {
7. var hit : RaycastHit;
8.     if (Physics.Raycast (camera.ScreenPointToRay(Input.mousePosition), hit)){
9.         HighlightSelectedFace(hit);
10.     }
11.     else {
12.         RemoveHighlights();
13.     }
14. }
15.  
16.  
17. function HighlightSelectedFace(hit : RaycastHit){
18.     if (lastHitNormal != Vector3.zero){
19.         RemoveHighlights();
20.     }
21.     var meshCollider = hit.collider as MeshCollider;
22.     if (meshCollider == null || meshCollider.sharedMesh == null)
23.     return;
24.  
25.     var mesh : Mesh = meshCollider.sharedMesh;
26.     var vertices = mesh.vertices;
27.     var normals = mesh.normals;
28.     var triangles = mesh.triangles;
29.     var colors = new Color[vertices.Length];
30.  
31.     for (var i=0;i<vertices.length;i++){
32.         if (normals[i] == hit.normal){
33.             colors[i] = highlightColor;
34.         }
35.         else {
36.             colors[i] = Color.white;   
37.         }
38.     }
39.  
40.     mesh.colors = colors;
41.     lastMesh = mesh;
42.     lastHitNormal = hit.normal;
43.  
44. }
45.  
46.  
47. function RemoveHighlights(){
48.     if (lastMesh){
49.         var mesh : Mesh = lastMesh;
50.         var vertices = mesh.vertices;
51.         var normals = mesh.normals;
52.         var triangles = mesh.triangles;
53.         var originalColors = mesh.colors;
54.         var colors = new Color[vertices.Length];
55.  
56.         for (var i=0;i<vertices.length;i++){
57.             colors[i] = Color.white;
58.         }
59.  
60.         mesh.colors = colors;
61.         lastMesh = null;
62.         lastHitNormal = Vector3.zero;
63.     }
64. }
65.  

The example below uses a Unity cube primitive with a mesh collider. The code is pretty simple and fast. I am sure it can be improved, but it is enough to get you started.

Click here for the webplayer.

I also came to realize that very few of the default Unity shaders support vertex colors, so below I have attached my shader. It is a simple shader from the wiki that I hacked an outline into.

Enjoy!