Creating a Normal Map within a Shader

Hey guys, I am attempting to convert an old c# ripple effect into a shader to quicken performance, I use to take the 0-1 range and apply it to the pixels as so

Code (CSharp):

1. for (int y=0; y < bumpTexture.height; ++y) {
2.       for (int x=0; x < bumpTexture.width; ++x) {
3.  
4.              float xLeft = BumpMap.GetPixel(x-1,y).grayscale;
5.  
6.              float xRight = BumpMap.GetPixel(x+1,y).grayscale;
7.  
8.              float yUp = BumpMap.GetPixel(x,y-1).grayscale;
9.  
10.              float yDown = BumpMap.GetPixel(x,y+1).grayscale;
11.  
12.              float xDelta = ((xLeft-xRight)+1)*0.5f;
13.  
14.              float yDelta = ((yUp-yDown)+1)*0.5f;
15.  
16.          
17.         bumpTexture.SetPixel(x,y,new Color(xDelta,yDelta,1.0f,1.0f));
18.        }
19. }        

but using an example from a unity asset, I am attempting to use a render texture in place of setting all the pixels manually, but applying the normal map fixed4 of 0.5,0.5,1,1. However that is not as simple as I thought.

Code (CSharp):

1. fixed4 frag(v2f i) : COLOR
2.     {
3.         fixed orig = tex2D(_MainTex, i.uv[0]).r;
4.         return orig + step(1 - _DropSize, 1 - length(_MousePos.xy - i.uv[1]));
5.     }
6.  
7.     fixed4 fragPropogate(v2f i) : COLOR
8.     {
9.         float sample = tex2D(_MainTex, i.uv[1]).r;
10.         sample += tex2D(_MainTex, i.uv[2]).r;
11.         sample += tex2D(_MainTex, i.uv[3]).r;
12.         sample += tex2D(_MainTex, i.uv[4]).r;
13.  
14.         sample /= 4.0;
15.  
16.         float newValue = sample * 2.0 + -tex2D(_PrevTex, i.uv[0]).r;
17.  
18.         return newValue * _Damping;
19.     }

Right now there are white ripples on a black texture, ive tried multiple approaches like changing the format of the render texture, manually manipulating the rgba of the fixed4. What am I missing?

 

Texture set to wrap etc? also check your uvs have valid data. It should be showing something.

 

UVs seem to be fine, as for the output, using the Frag on a _maintex is fine, but applying it on a _bumpmap yeilds nothing.