shader原理，读取屏幕像素进行处理，再返回纹理

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

Shader "my/FrostedGlass"
{
    Properties
    {
        _blurSizeXY("BlurSizeXY", Range(0,10)) = 2
    }
        SubShader
    {
        // 透明队列，在所有不透明的几何图形后绘制
        Tags { "Queue" = "Transparent" }

        // 采样后面的图像
        GrabPass { }

        Pass
        {
            CGPROGRAM
            #pragma target 3.0
            #pragma debug
            #pragma vertex vert
            #pragma fragment frag

            sampler2D _GrabTexture : register(s0);
            float _blurSizeXY;

            struct data
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };
            struct v2f
            {
                float4 position : POSITION;
                float4 screenPos : TEXCOORD0;
            };

            v2f vert(data i)
            {
                v2f o;
                o.position = UnityObjectToClipPos(i.vertex);
                o.screenPos = float4(o.position.x, o.position.y, o.position.z, o.position.w);
                return o;
            }

            half4 frag(v2f i) : COLOR
            {
                float2 screenPos = i.screenPos.xy / i.screenPos.w;
                float depth = _blurSizeXY * 0.0005;

                screenPos.x = (screenPos.x + 1) * 0.5;
                screenPos.y = 1 - (screenPos.y + 1) * 0.5;

                half4 sum = half4(0,0,0,0);

                sum += tex2D(_GrabTexture, float2(screenPos.x - 5.0 * depth, screenPos.y + 5.0 * depth)) * 0.025;
                sum += tex2D(_GrabTexture, float2(screenPos.x + 5.0 * depth, screenPos.y - 5.0 * depth)) * 0.025;

                sum += tex2D(_GrabTexture, float2(screenPos.x - 4.0 * depth, screenPos.y + 4.0 * depth)) * 0.05;
                sum += tex2D(_GrabTexture, float2(screenPos.x + 4.0 * depth, screenPos.y - 4.0 * depth)) * 0.05;

                sum += tex2D(_GrabTexture, float2(screenPos.x - 3.0 * depth, screenPos.y + 3.0 * depth)) * 0.09;
                sum += tex2D(_GrabTexture, float2(screenPos.x + 3.0 * depth, screenPos.y - 3.0 * depth)) * 0.09;

                sum += tex2D(_GrabTexture, float2(screenPos.x - 2.0 * depth, screenPos.y + 2.0 * depth)) * 0.12;
                sum += tex2D(_GrabTexture, float2(screenPos.x + 2.0 * depth, screenPos.y - 2.0 * depth)) * 0.12;

                sum += tex2D(_GrabTexture, float2(screenPos.x - 1.0 * depth, screenPos.y + 1.0 * depth)) * 0.15;
                sum += tex2D(_GrabTexture, float2(screenPos.x + 1.0 * depth, screenPos.y - 1.0 * depth)) * 0.15;

                sum += tex2D(_GrabTexture, screenPos - 5.0 * depth) * 0.025;
                sum += tex2D(_GrabTexture, screenPos - 4.0 * depth) * 0.05;
                sum += tex2D(_GrabTexture, screenPos - 3.0 * depth) * 0.09;
                sum += tex2D(_GrabTexture, screenPos - 2.0 * depth) * 0.12;
                sum += tex2D(_GrabTexture, screenPos - 1.0 * depth) * 0.15;
                sum += tex2D(_GrabTexture, screenPos) * 0.16;
                sum += tex2D(_GrabTexture, screenPos + 5.0 * depth) * 0.15;
                sum += tex2D(_GrabTexture, screenPos + 4.0 * depth) * 0.12;
                sum += tex2D(_GrabTexture, screenPos + 3.0 * depth) * 0.09;
                sum += tex2D(_GrabTexture, screenPos + 2.0 * depth) * 0.05;
                sum += tex2D(_GrabTexture, screenPos + 1.0 * depth) * 0.025;

                return sum / 2;
            }
            ENDCG
        }
    }
        Fallback Off
}