Shader"MyShader/GaussianBlurMask"
{
    Properties
    {
        [PerRendererData] _MainTex ("Texture", 2D) = "white" {}
        _BlurSize ("Blur Size", Float) = 1.0
    }
    SubShader
    {
        Tags { "Queue"="Transparent" "RenderType"="Transparent" "IgnoreProjector"="True"}
Cull Off
Lighting Off
ZWrite Off
ZTest[unity_GUIZTestMode]
Blend SrcAlpha
OneMinusSrcAlpha
 
        GrabPass
{
} //不带参数名，默认抓取到_GrabTexture，否则只会抓取一次
 
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
 
#include "UnityCG.cginc"
 
struct a2v
{
    float4 vertex : POSITION;
    float4 color : COLOR;
    float2 uv : TEXCOORD0;
};
 
struct v2f
{
    float4 pos : SV_POSITION;
    float4 scrPos : TEXCOORD0;
    float2 uv : TEXCOORD1;
    fixed4 color : TEXCOORD2;
};
 
sampler2D _MainTex;
float4 _MainTex_ST;
float _BlurSize;
 
sampler2D _GrabTexture; //GrabPass抓取的纹理
float4 _GrabTexture_TexelSize; //纹理大小
 
v2f vert(a2v v)
{
    v2f o;
    o.pos = UnityObjectToClipPos(v.vertex);
    o.scrPos = ComputeGrabScreenPos(o.pos); //抓取屏幕的坐标
    o.uv = TRANSFORM_TEX(v.uv, _MainTex);
    o.color = v.color;
    return o;
}
 
fixed4 frag(v2f i) : SV_Target
{
    fixed4 diffuse = tex2D(_MainTex, i.uv);
    fixed4 col = diffuse * i.color;
 
    float weight[3] = { 0.4026, 0.2442, 0.0545 }; //一维5*5高斯滤波参数，乘起来就是二维的正态分布
    fixed3 sum = fixed3(0, 0, 0);
 
    for (int x = -2; x <= 2; x++)
    {
        for (int y = -2; y <= 2; y++)
        {
            fixed2 offset = fixed2(x, y) * _GrabTexture_TexelSize.xy * _BlurSize;
            fixed2 cur_UVxy = offset * i.scrPos.z + i.scrPos.xy;
            sum += tex2D(_GrabTexture, cur_UVxy / i.scrPos.w).rgb * weight[abs(x)] * weight[abs(y)];
        }
    }
    return col * fixed4(sum, 1);
}
            ENDCG
        }
    }
}