color shifting displacement feedback process implemented as a unity3d postprocessing shader

PostEffect.shader

Shader "Jars/PostEffect"
{
    HLSLINCLUDE

        #include "../PostProcessing/Shaders/StdLib.hlsl"

        TEXTURE2D_SAMPLER2D(_MainTex, sampler_MainTex);
        float _Blend;

        float4 Frag(VaryingsDefault i) : SV_Target
        {
            float4 prelook = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoord);
            float4 color2 = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoord + ((prelook.rb - 0.5) / 200.0));
            
            float4 shiftAmount = float4(0.005, 0.01, 0.015, 0.0);

            return (color2 + shiftAmount) % 1.0;;
        }

    ENDHLSL

    SubShader
    {
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            HLSLPROGRAM

                #pragma vertex VertDefault
                #pragma fragment Frag

            ENDHLSL
        }
    }
}