ui 模糊 shader

build in 环境
不适用于urp hdrp

被ui覆盖部分将会产生模糊

效果

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

// Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)
Shader "UI/Blurred"
{
    Properties
    {
        [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
        _Size("Blur Radius", Range(0,4)) = 1
    }

        SubShader
        {
            Tags
        {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "Transparent"
            "PreviewType" = "Plane"
            "CanUseSpriteAtlas" = "True"
        }
            Cull Off
            Lighting Off
            ZWrite Off
            ZTest Always
            Blend SrcAlpha OneMinusSrcAlpha

            // Horizontal blur
        GrabPass{
            Tags{ "LightMode" = "Always" }
        }
            Pass{
            Tags{ "LightMode" = "Always" }

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

        struct appdata_t {
            float4 vertex : POSITION;
            float2 texcoord: TEXCOORD0;
        };

        struct v2f {
            float4 vertex : POSITION;
            float4 uvgrab : TEXCOORD0;
        };

        v2f vert(appdata_t v) {
            v2f o;
            o.vertex = UnityObjectToClipPos(v.vertex);
#if UNITY_UV_STARTS_AT_TOP
            float scale = -1.0;
#else
            float scale = 1.0;
#endif
            o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y * scale) + o.vertex.w) * 0.5;
            o.uvgrab.zw = o.vertex.zw;
            return o;
        }

        sampler2D _GrabTexture;
        float4 _GrabTexture_TexelSize;
        float _Size;

        half4 frag(v2f i) : COLOR{

            half4 sum = half4(0,0,0,0);
#define BLURPIXEL(weight,kernelx) tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x + _GrabTexture_TexelSize.x * kernelx*_Size, i.uvgrab.y, i.uvgrab.z, i.uvgrab.w))) * weight
            sum += BLURPIXEL(0.05, -4.0);
            sum += BLURPIXEL(0.09, -3.0);
            sum += BLURPIXEL(0.12, -2.0);
            sum += BLURPIXEL(0.15, -1.0);
            sum += BLURPIXEL(0.18,  0.0);
            sum += BLURPIXEL(0.15, +1.0);
            sum += BLURPIXEL(0.12, +2.0);
            sum += BLURPIXEL(0.09, +3.0);
            sum += BLURPIXEL(0.05, +4.0);

            return sum;
        }
            ENDCG
        }
            // Vertical blur
            GrabPass{
            Tags{ "LightMode" = "Always" }
        }
            Pass{
            Tags{ "LightMode" = "Always" }

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

            struct appdata_t {
            float4 vertex : POSITION;
            float4 color    : COLOR;
            float2 texcoord: TEXCOORD0;
        };

        struct v2f {
            float4 vertex : POSITION;
            float4 uvgrab : TEXCOORD0;
            fixed4 color : COLOR;
        };

        v2f vert(appdata_t v) {
            v2f o;
            o.vertex = UnityObjectToClipPos(v.vertex);
#if UNITY_UV_STARTS_AT_TOP
            float scale = -1.0;
#else
            float scale = 1.0;
#endif
            o.uvgrab.xy = (float2(o.vertex.x, o.vertex.y * scale) + o.vertex.w) * 0.5;
            o.uvgrab.zw = o.vertex.zw;
            return o;
        }

        sampler2D _GrabTexture;
        float4 _GrabTexture_TexelSize;
        float _Size;

        half4 frag(v2f i) : COLOR{

            half4 sum = half4(0,0,0,0);
#define BLURPIXEL(weight,kernely) tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(float4(i.uvgrab.x, i.uvgrab.y + _GrabTexture_TexelSize.y * kernely * _Size, i.uvgrab.z, i.uvgrab.w))) * weight

            sum += BLURPIXEL(0.05, -4.0);
            sum += BLURPIXEL(0.09, -3.0);
            sum += BLURPIXEL(0.12, -2.0);
            sum += BLURPIXEL(0.15, -1.0);
            sum += BLURPIXEL(0.18,  0.0);
            sum += BLURPIXEL(0.15, +1.0);
            sum += BLURPIXEL(0.12, +2.0);
            sum += BLURPIXEL(0.09, +3.0);
            sum += BLURPIXEL(0.05, +4.0);

            return sum;
        }
            ENDCG
        }

        Pass
        {
            Name "Default"
            CGPROGRAM
    #pragma vertex vert
    #pragma fragment frag
    #pragma target 2.0

    #include "UnityCG.cginc"
    #include "UnityUI.cginc"

    #pragma multi_compile __ UNITY_UI_CLIP_RECT
    #pragma multi_compile __ UNITY_UI_ALPHACLIP

            struct appdata_t
        {
            float4 vertex   : POSITION;
            float4 color    : COLOR;
            float2 texcoord : TEXCOORD0;
            UNITY_VERTEX_INPUT_INSTANCE_ID
        };

        struct v2f
        {
            float4 vertex   : SV_POSITION;
            fixed4 color : COLOR;
            float2 texcoord  : TEXCOORD0;
            float4 worldPosition : TEXCOORD1;
            float4 uvgrab : TEXCOORD2;
        };

        sampler2D _MainTex;
        sampler2D _GrabTexture;
        float4 _GrabTexture_TexelSize;
        fixed4 _TextureSampleAdd;
        float4 _ClipRect;
        float4 _MainTex_ST;

        v2f vert(appdata_t v)
        {
            v2f OUT;
            UNITY_SETUP_INSTANCE_ID(v);
            UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
            OUT.worldPosition = v.vertex;
            OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);

            OUT.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
#if UNITY_UV_STARTS_AT_TOP
            float scale = -1.0;
#else
            float scale = 1.0;
#endif
            OUT.uvgrab.xy = (float2(OUT.vertex.x, OUT.vertex.y * scale) + OUT.vertex.w) * 0.5;
            OUT.uvgrab.zw = OUT.vertex.zw;

            OUT.color = v.color;
            return OUT;
        }

        fixed4 frag(v2f IN) : SV_Target
        {
            half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
            half4 blur = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(IN.uvgrab));
            return color;
        }
            ENDCG
        }
        }
}

来源：如何做出好看的ui效果    https://www.youtube.com/watch?v=HwdweCX5aMI