World Relative UVs with normalmaps

Hello !
I am currently using a shader allowing me to place my texture relative to the world. I simply put the textures used for the floor (normals pointing up) and for the walls (normals pointing elsewhere).

Code (csharp):

1.  
2. struct Input
3. {
4.     float3 worldNormal;
5.     float3 worldPos;
6. };
7.  
8.  
9. void surf (Input IN, inout SurfaceOutput o)
10. {
11. float2 UV;
12. fixed4 c;
13.  
14.     if(abs(IN.worldNormal.x)>0.5)
15.     {
16.         UV = IN.worldPos.zy; // side
17.         c = tex2D(_MainTexWall, UV* _Scale); // use WALLSIDE texture
18.     }
19.     else if(abs(IN.worldNormal.z)>0.5)
20.     {
21.         UV = IN.worldPos.xy; // front
22.         c = tex2D(_MainTexWall, UV* _Scale); // use WALL texture
23.     }
24.     else
25.     {
26.         UV = IN.worldPos.xz; // top
27.         c = tex2D(_MainTexFlr, UV* _FlrScale); // use FLR texture
28.     }
29.  
30. o.Albedo = c.rgb;
31. }
32.  

I want to add normalmapping to this shader. Some of you might already know what my question is going to be since the problem is written in the doc :

I can't read worldNormal as soon as I add

Code (csharp):

1.  o.Normal = something

and

Code (csharp):

1.  
2. struct Input
3. {
4.     float3 worldNormal;
5.     float3 worldPos;
6.         INTERNAL_DATA
7. };
8.  

But using WorldNormalVector(IN, o.Normal) doesn't seem to do much if i haven't changed the value of o.Normal before...

I feel like in order to read my worldNormal, I need to write it myself, which doesn't seem possible since I can't read it...

So, does anybody have any idea so I can add normalmapping to my textures ?

Thanks a lot for your help !

 

Here is the solution by Orihaus in the comments of http://www.blog.radiator.debacle.us/2012/01/joys-of-using-world-space-procedural.html

Code (csharp):

1.  
2.     Shader "WorldUV/Bumped Diffuse" {
3.         Properties
4.         {
5.                 _MainTex ("Base", 2D) = "white" {}
6.                 _BumpMap ("Normalmap", 2D) = "bump" {}
7.                 _Scale ("Scale", float) = 1.0
8.         }
9.        
10.         SubShader
11.         {
12.                 Tags { "RenderType"="Opaque" }
13.                 LOD 400
14.        
15.                 CGPROGRAM
16.                 #pragma surface surf Lambert
17.                
18.                
19.                 struct Input
20.                 {
21.                     float4 color : COLOR;
22.                         float2 uv_MainTex;
23.                         float2 uv_BumpMap;
24.                         float3 worldPos;
25.                         float3 worldNormal; INTERNAL_DATA
26.                 };
27.                
28.                 sampler2D _MainTex;
29.                 sampler2D _BumpMap;
30.                 fixed4 _Color;
31.                
32.                 half _Scale;
33.                
34.                 void surf (Input IN, inout SurfaceOutput o)
35.                 {
36.                         float3 correctWorldNormal = WorldNormalVector(IN, float3( 0, 0, 1 ) );
37.                         float2 uv = IN.worldPos.zx;
38.                        
39.                         if( abs( correctWorldNormal.x ) > 0.5 ) uv = IN.worldPos.zy;
40.                         if( abs( correctWorldNormal.z ) > 0.5 ) uv = IN.worldPos.xy;
41.  
42.                         uv.x *= _Scale;
43.                         uv.y *= _Scale;
44.                        
45.                         fixed4 tex = tex2D( _MainTex, uv );
46.                         o.Albedo = IN.color * tex.rgb ;
47.                         o.Normal = UnpackNormal( tex2D( _BumpMap, uv ) );
48.                 }
49.                
50.                 ENDCG
51.         }
52.     FallBack "Bumped Specular"
53.     }
54.