how to create a magnify or pinch effect using a perlin noise map for UVs

Hello!
Like the subject, I am trying to create some variation for a texture by distorting the UV map.
I am looking for a way to create a magnify / pinch effect using a perlin noise map. (or cloud map)
This is not a flowmap, it should make the texture on some areas slightly bigger, more organic.

Does one know how to that?

regards! Tom

 

Using a texture to displace a UV is fairly trivial, but just using the noise straight will never get you the pinch / zoom look you want, for that you need something like a normal map which you can generate from any noise pattern either offline or in the shader.

The basic noise UV displacement would be something like this.

float noise = tex2d(_NoiseTex, i.uv).r; // or some noise function
float2 displacedUV = i.uv + noise * _UVNoiseScale;
fixed4 albedo = tex2d(_MainTex, displacedUV);

If you do this then the texture just looks wavy rather than pinch and zoom. Now as I said you can just take a noise texture and do a height to normal map in an external program or on import and store it as a normal map, in which case you'd treat it similar to a normal map in the shader but not quite.

float2 noise = tex2d(_NoiseTex, i.uv).ag;

The last option is the one where you generate the same "slope" information that a normal map would have in the shader. This is useful if you're using a noise function instead of a texture.

float noise = tex2d(_NoiseTex, i.uv).r;
float noiseU = tex2d(_NoiseTex, i.uv + float2(_NoiseTex_TexelSize.x, 0.0)).r;
float noiseV = tex2d(_NoiseTex, i.uv + float2(0.0, _NoiseTex_TexelSize.y)).r;
float2 displacedUV = i.uv + float2(noiseU - noise, noiseV - noise) * _UVNoiseScale;