Shader "MyShader/GaussianBlur" { // 高斯模糊
    Properties{
        _MainTex("Base (RGB)", 2D) = "white" {} // 主纹理
        _BlurSize("Blur Size", Float) = 1.0 // 模糊尺寸(纹理坐标的偏移量)
    }

        SubShader{
            CGINCLUDE

            #include "UnityCG.cginc"

            sampler2D _MainTex; // 主纹理
            half4 _MainTex_TexelSize; // _MainTex的像素尺寸大小, float4(1/width, 1/height, width, height)
            float _BlurSize; // 模糊尺寸(纹理坐标的偏移量)

            struct v2f {
                float4 pos : SV_POSITION; // 模型空间顶点坐标
                half2 uv[5]: TEXCOORD0; // 5个邻域的纹理坐标
            };

            v2f vertBlurVertical(appdata_img v) { // 垂直模糊顶点着色器
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex); // 模型空间顶点坐标变换到裁剪空间, 等价于: mul(UNITY_MATRIX_MVP, v.vertex)
                half2 uv = v.texcoord;
                o.uv[0] = uv;
                o.uv[1] = uv + float2(0.0, _MainTex_TexelSize.y * 1.0) * _BlurSize;
                o.uv[2] = uv - float2(0.0, _MainTex_TexelSize.y * 1.0) * _BlurSize;
                o.uv[3] = uv + float2(0.0, _MainTex_TexelSize.y * 2.0) * _BlurSize;
                o.uv[4] = uv - float2(0.0, _MainTex_TexelSize.y * 2.0) * _BlurSize;
                return o;
            }

            v2f vertBlurHorizontal(appdata_img v) { // 水平模糊顶点着色器
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex); // 模型空间顶点坐标变换到裁剪空间, 等价于: mul(UNITY_MATRIX_MVP, v.vertex)
                half2 uv = v.texcoord;
                o.uv[0] = uv;
                o.uv[1] = uv + float2(_MainTex_TexelSize.x * 1.0, 0.0) * _BlurSize;
                o.uv[2] = uv - float2(_MainTex_TexelSize.x * 1.0, 0.0) * _BlurSize;
                o.uv[3] = uv + float2(_MainTex_TexelSize.x * 2.0, 0.0) * _BlurSize;
                o.uv[4] = uv - float2(_MainTex_TexelSize.x * 2.0, 0.0) * _BlurSize;
                return o;
            }

            fixed4 fragBlur(v2f i) : SV_Target {
                float weight[3] = {0.4026, 0.2442, 0.0545}; // 大小为5的一维高斯核，实际只需记录3个权值
                fixed3 sum = tex2D(_MainTex, i.uv[0]).rgb * weight[0];
                for (int j = 1; j < 3; j++) {
                    sum += tex2D(_MainTex, i.uv[j * 2 - 1]).rgb * weight[j]; // 中心右侧或下侧的纹理*权值
                    sum += tex2D(_MainTex, i.uv[j * 2]).rgb * weight[j]; // 中心左侧或上侧的纹理*权值
                }
                return fixed4(sum, 1.0);
            }

            ENDCG

            ZTest Always Cull Off ZWrite Off

            Pass {
                NAME "GAUSSIAN_BLUR_VERTICAL"

                CGPROGRAM

                #pragma vertex vertBlurVertical  
                #pragma fragment fragBlur

                ENDCG
            }

            Pass {
                NAME "GAUSSIAN_BLUR_HORIZONTAL"

                CGPROGRAM

                #pragma vertex vertBlurHorizontal  
                #pragma fragment fragBlur

                ENDCG
            }
        }

            FallBack "Diffuse"
}