因为Unity 提供了GrabPass，可以在Shader中很方便的拿到Panel下面的图像，即_GrabTexture。
注：添加优化。原本的搞死模糊效果达不到苹果的那种细腻效果，修改参数即可。
修改两个#define，kernelx*_Size ->kernelx*_Size * 1.61
Shader "Custom/SimpleGrabPassBlur" {Properties {_Color ("Main Color", Color) = (1,1,1,1)_BumpAmt ("Distortion", Range (0,128)) = 10_MainTex ("Tint Color (RGB)", 2D) = "white" {}_BumpMap ("Normalmap", 2D) = "bump" {}_Size ("Size", Range(0, 20)) = 1}Category {// We must be transparent, so other objects are drawn before this one.Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Opaque" }SubShader {// Horizontal blurGrabPass {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 = mul(UNITY_MATRIX_MVP, v.vertex);#if UNITY_UV_STARTS_AT_TOPfloat scale = -1.0;#elsefloat scale = 1.0;#endifo.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 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));// return col;half4 sum = half4(0,0,0,0);#define GRABPIXEL(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))) * weightsum += GRABPIXEL(0.05, -4.0);sum += GRABPIXEL(0.09, -3.0);sum += GRABPIXEL(0.12, -2.0);sum += GRABPIXEL(0.15, -1.0);sum += GRABPIXEL(0.18, 0.0);sum += GRABPIXEL(0.15, +1.0);sum += GRABPIXEL(0.12, +2.0);sum += GRABPIXEL(0.09, +3.0);sum += GRABPIXEL(0.05, +4.0);return sum;}ENDCG}// Vertical blurGrabPass { 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 = mul(UNITY_MATRIX_MVP, v.vertex);#if UNITY_UV_STARTS_AT_TOPfloat scale = -1.0;#elsefloat scale = 1.0;#endifo.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 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));// return col;half4 sum = half4(0,0,0,0);#define GRABPIXEL(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//G(X) = (1/(sqrt(2*PI*deviation*deviation))) * exp(-(x*x / (2*deviation*deviation)))sum += GRABPIXEL(0.05, -4.0);sum += GRABPIXEL(0.09, -3.0);sum += GRABPIXEL(0.12, -2.0);sum += GRABPIXEL(0.15, -1.0);sum += GRABPIXEL(0.18, 0.0);sum += GRABPIXEL(0.15, +1.0);sum += GRABPIXEL(0.12, +2.0);sum += GRABPIXEL(0.09, +3.0);sum += GRABPIXEL(0.05, +4.0);return sum;}ENDCG}// DistortionGrabPass { 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;float2 uvbump : TEXCOORD1;float2 uvmain : TEXCOORD2;};float _BumpAmt;float4 _BumpMap_ST;float4 _MainTex_ST;v2f vert (appdata_t v) {v2f o;o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);#if UNITY_UV_STARTS_AT_TOPfloat scale = -1.0;#elsefloat scale = 1.0;#endifo.uvgrab.xy = (float2(o.vertex.x, o.vertex.y*scale) + o.vertex.w) * 0.5;o.uvgrab.zw = o.vertex.zw;o.uvbump = TRANSFORM_TEX( v.texcoord, _BumpMap );o.uvmain = TRANSFORM_TEX( v.texcoord, _MainTex );return o;}fixed4 _Color;sampler2D _GrabTexture;float4 _GrabTexture_TexelSize;sampler2D _BumpMap;sampler2D _MainTex;half4 frag( v2f i ) : COLOR {// calculate perturbed coordinateshalf2 bump = UnpackNormal(tex2D( _BumpMap, i.uvbump )).rg; // we could optimize this by just reading the x y without reconstructing the Zfloat2 offset = bump * _BumpAmt * _GrabTexture_TexelSize.xy;i.uvgrab.xy = offset * i.uvgrab.z + i.uvgrab.xy;half4 col = tex2Dproj( _GrabTexture, UNITY_PROJ_COORD(i.uvgrab));half4 tint = tex2D( _MainTex, i.uvmain ) * _Color;return col * tint;}ENDCG}}}}
使用：
新建Panel->去掉Source Image->material处添加此shader的材质球。该Panel即可对背后的显示实现高斯模糊效果。
转自：Unity 毛玻璃效果（UGUI）—高斯模糊
