// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "RapidBlurEffect"
{
    Properties
    {
        _MainTex("Base (RGB)", 2D) = "white" {}
    }

    SubShader
    {
        ZWrite Off
        Blend Off

        Pass
        {
            ZTest Off
            Cull Off

            CGPROGRAM
            #pragma vertex vert_DownSmpl
            #pragma fragment frag_DownSmpl
            ENDCG
        }

        Pass
        {
            ZTest Always
            Cull Off

            CGPROGRAM
            #pragma vertex vert_BlurVertical
            #pragma fragment frag_Blur
            ENDCG
        }

        Pass
        {
            ZTest Always
            Cull Off

            CGPROGRAM
            #pragma vertex vert_BlurHorizontal
            #pragma fragment frag_Blur
            ENDCG
        }
    }

    CGINCLUDE

    #include "UnityCG.cginc"

    sampler2D _MainTex;
    uniform half4 _MainTex_TexelSize;
    uniform half _DownSampleValue;

    struct VertexInput
    {
        float4 vertex : POSITION;
        half2 texcoord : TEXCOORD0;
    };

    struct VertexOutput_DownSmpl
    {
        float4 pos : SV_POSITION;
        half2 uv20 : TEXCOORD0;
        half2 uv21 : TEXCOORD1;
        half2 uv22 : TEXCOORD2;
        half2 uv23 : TEXCOORD3;
    };

    static const half4 GaussWeight[7] =
    {
        half4(0.0205,0.0205,0.0205,0),
        half4(0.0855,0.0855,0.0855,0),
        half4(0.232,0.232,0.232,0),
        half4(0.324,0.324,0.324,1),
        half4(0.232,0.232,0.232,0),
        half4(0.0855,0.0855,0.0855,0),
        half4(0.0205,0.0205,0.0205,0)
    };

    VertexOutput_DownSmpl vert_DownSmpl(VertexInput v)
    {
        VertexOutput_DownSmpl o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.uv20 = v.texcoord + _MainTex_TexelSize.xy* half2(0.5h, 0.5h);;
        o.uv21 = v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h, -0.5h);
        o.uv22 = v.texcoord + _MainTex_TexelSize.xy * half2(0.5h, -0.5h);
        o.uv23 = v.texcoord + _MainTex_TexelSize.xy * half2(-0.5h, 0.5h);
        return o;
    }

    fixed4 frag_DownSmpl(VertexOutput_DownSmpl i) : SV_Target
    {
        fixed4 color = (0,0,0,0);
        color += tex2D(_MainTex, i.uv20);
        color += tex2D(_MainTex, i.uv21);
        color += tex2D(_MainTex, i.uv22);
        color += tex2D(_MainTex, i.uv23);
        return color / 4;
    }

    struct VertexOutput_Blur
    {
        float4 pos : SV_POSITION;
        half4 uv : TEXCOORD0;
        half2 offset : TEXCOORD1;
    };

    VertexOutput_Blur vert_BlurHorizontal(VertexInput v)
    {
        VertexOutput_Blur o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.uv = half4(v.texcoord.xy, 1, 1);
        o.offset = _MainTex_TexelSize.xy * half2(1.0, 0.0) * _DownSampleValue;
        return o;
    }

    VertexOutput_Blur vert_BlurVertical(VertexInput v)
    {
        VertexOutput_Blur o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.uv = half4(v.texcoord.xy, 1, 1);
        o.offset = _MainTex_TexelSize.xy * half2(0.0, 1.0) * _DownSampleValue;
        return o;
    }

    half4 frag_Blur(VertexOutput_Blur i) : SV_Target
    {
        half2 uv = i.uv.xy;
        half2 OffsetWidth = i.offset;
        half2 uv_withOffset = uv - OffsetWidth * 3.0;
        half4 color = 0;
        for (int j = 0; j< 7; j++)
        {
            half4 texCol = tex2D(_MainTex, uv_withOffset);
            color += texCol * GaussWeight[j];
            uv_withOffset += OffsetWidth;
        }
        return color;
    }

    ENDCG

    FallBack Off
}