Shader "Heat Haze"
{
    Properties
    {
        _MainTex ("Base (RGB)", RECT) = "white" {}
        _DisortTex ("Disortion Normal (RGB)", 2D) = "white" {}
        _DisortStrength ("Disortion Strength", Float) = 0.1
        _DisortSpeed ("Disortion Strength", Vector) = (0.0, 1.0, 0.0, 0.0)
    }

    SubShader
    {
        Pass
        {
            ZTest Always
            Cull Off
            ZWrite Off
            Fog { Mode off }

            CGPROGRAM
                #pragma vertex vert_img
                #pragma fragment frag
                #pragma fragmentoption ARB_precision_hint_fastest
                #include "UnityCG.cginc"

                uniform samplerRECT _MainTex;
                uniform sampler2D _DisortTex;
                uniform float _DisortStrength;
                uniform float4 _DisortSpeed;

                float4 frag (v2f_img i) : COLOR
                {
                    float4 disortion = tex2D(_DisortTex, i.uv)*2.0-1.0;
                    disortion = normalize(disortion);

                    float4 original = texRECT(_MainTex, i.uv+disortion.rg*_DisortStrength+_DisortSpeed*_Time.x);

                    return original;
                }
            ENDCG
        }
    }

    Fallback off
}