Surface Shader 'vert' function texture lookups

Hello!

I'm trying to write a surface shader that uses a noise texture for vertex displacement. However, I am getting a compile error when trying to do a texture lookup in the 'vert' function.

Here is the code for the shader (obviously not finished, don't point and laugh! )

Code (csharp):

1.   Shader "Test/Noise" {
2.     Properties {
3.       _MainTex ("Texture", 2D) = "white" {}
4.       _NoiseTex("Noise", 2D) = "white" {}
5.       _TimeScale ("Time Scaling", Range(0,10)) = 1.0
6.       _Displacement("Displacement", Range(0,5)) = 1.0
7.     }
8.     SubShader {
9.       Tags { "RenderType" = "Opaque" }
10.       CGPROGRAM
11.  
12.       #pragma target 3.0
13.           #pragma surface surf Lambert vertex:vert
14.          
15.       float _Sharpness;
16.       float _Displacement;
17.       float _TimeScale;
18.       sampler2D _NoiseTex;
19.      
20.       void vert(inout appdata_full v)
21.       {
22.         float2 uvHack = float2(frac(v.vertex.x + v.vertex.y + v.vertex.z),
23.                                 frac(v.vertex.x * v.vertex.y * v.vertex.z));
24.        
25.         float3 noise = tex2D(_NoiseTex,uvHack).rgb;
26.        
27.         v.vertex.xyz = v.vertex.xyz - (v.normal.xyz * (noise.x * _Displacement));
28.       }
29.      
30.           sampler2D _MainTex;
31.      
32.           struct Input {
33.               float2 uv_MainTex;
34.           };
35.  
36.           void surf (Input IN, inout SurfaceOutput o) {
37.          
38.               o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb;
39.           }
40.  
41.       ENDCG
42.     }
43.     Fallback "Diffuse"
44.   }

Is it even possible to do this with a surface shader? I've never even tried this, and some googling informed me that it is possible (dependant on hardware) if I write out the vertex and fragment shaders separately, but I would like the functionality of using the surface shader to handle lighting.

I'm new to unity/ShaderLab, but I have some experience with CgFX, so I have a fairly good grasp of what is going on, I'm just not sure if what I want to do is possible or not.

 

Thanks, tex2Dlod() worked! This thread has more detail on the matter:

http://forum.unity3d.com/threads/63231-How-to-use-vertex-texture-fetch

I didn't notice it before I posted this thread :/

Thanks for the help!