首先URP官方已经给了很详细的实现方案，知乎参考链接：https://zhuanlan.zhihu.com/p/248903320
原理就是在渲染所有3D和UI之后通过URP的Cbuffer shader进行屏幕抓取，然后再对抓到的图进行高斯模糊，然后映射到指定的毛玻璃效果的图上。
URP设置
默认的ForwardRender里 层级过滤设为所有，UI层级也好，毛玻璃层级也好都需要被渲染
GrabColor里：通过指定的Blurshader指定抓屏的层级（去掉毛玻璃层），开启抓屏并保存，然后经过高斯模糊，输出到指定的TextureName的RT上。
对需要实现毛玻璃效果的物体添加毛玻璃材质球，此材质球的shader中使用上一步获得的RT，映射出毛玻璃效果
此操作涉及到三个重点：1.URP设置 2.抓屏shader 3.毛玻璃效果shader
抓屏Shader
Shader "WeiLe/Blur_Gaussian"
{
Properties
{
blurRangeX("Blur x", float) = 1
blurRangeY("Blur y", float) = 1
}
SubShader
{
Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline"}
LOD 100
Pass //pass 0
{
Name "BlurX"
ZTest Always
ZWrite Off
Cull Off
HLSLPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
struct Attributes
{
float4 positionOS : POSITION;
float2 uv : TEXCOORD0;
};
struct Varyings
{
float4 positionCS : SV_POSITION;
float2 uv : TEXCOORD0;
};
CBUFFER_START(UnityPerMaterial)
float4 _SourceTex_Blur1_ST;
float blurRangeX = 1;
float4 _SourceTex_Blur1_TexelSize;
CBUFFER_END
TEXTURE2D (_SourceTex_Blur1);
SAMPLER(sampler_SourceTex_Blur1);
#define SampleCount 10
Varyings vert(Attributes v)
{
Varyings o = (Varyings)0;
o.positionCS = TransformObjectToHClip(v.positionOS.xyz);
o.uv.xy = TRANSFORM_TEX(v.uv.xy, _SourceTex_Blur1);
return o;
}
half4 frag(Varyings i) : SV_Target
{
UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
half4 col = 0;
int s = 0;
for (int j = -SampleCount; j <= SampleCount; j++)
{
int a = SampleCount - abs(j) + 1;
s += a;
half4 c = a * SAMPLE_TEXTURE2D_X(_SourceTex_Blur1, sampler_SourceTex_Blur1, i.uv + float2(j* blurRangeX * _SourceTex_Blur1_TexelSize.x, 0));
col += c;
}
col /= s;
return col;
}
ENDHLSL
}
Pass //pass 1
{
Name "BlurY"
ZTest Always
ZWrite Off
Cull Off
HLSLPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
struct Attributes
{
float4 positionOS : POSITION;
float2 uv : TEXCOORD0;
};
struct Varyings
{
float4 positionCS : SV_POSITION;
float2 uv : TEXCOORD0;
};
CBUFFER_START(UnityPerMaterial)
float4 _SourceTex_Blur2_ST;
float4 _SourceTex_Blur2_TexelSize;
float blurRangeY = 1;
CBUFFER_END
TEXTURE2D(_SourceTex_Blur2);
SAMPLER(sampler_SourceTex_Blur2);
#define SampleCount 10
Varyings vert(Attributes v)
{
Varyings o = (Varyings)0;
o.positionCS = TransformObjectToHClip(v.positionOS.xyz);
o.uv.xy = TRANSFORM_TEX(v.uv.xy, _SourceTex_Blur2);
return o;
}
half4 frag(Varyings i) : SV_Target
{
UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
half4 col = 0;
int s = 0;
for (int j = -SampleCount; j <= SampleCount; j++)
{
int a = SampleCount - abs(j) + 1;
s += a;
half4 c = a*SAMPLE_TEXTURE2D_X(_SourceTex_Blur2, sampler_SourceTex_Blur2, i.uv + float2(0, j* blurRangeY * _SourceTex_Blur2_TexelSize.y));
col += c;
}
col /= s;
return col;
}
ENDHLSL
}
}
}
毛玻璃Shader
// Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)
Shader "UI/BlurUI_NoTexture"
{
Properties
{
[PerRendererData] _MainTex ("Sprite Texture", 2D) = "black" {}
_Color ("Tint", Color) = (1,1,1,1)
_StencilComp ("Stencil Comparison", Float) = 8
_Stencil ("Stencil ID", Float) = 0
_StencilOp ("Stencil Operation", Float) = 0
_StencilWriteMask ("Stencil Write Mask", Float) = 255
_StencilReadMask ("Stencil Read Mask", Float) = 255
_ColorMask ("Color Mask", Float) = 15
[Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0
}
SubShader
{
Tags
{
"Queue"="Transparent"
"IgnoreProjector"="True"
"RenderType"="Transparent"
"PreviewType"="Plane"
"CanUseSpriteAtlas"="True"
}
Stencil
{
Ref [_Stencil]
Comp [_StencilComp]
Pass [_StencilOp]
ReadMask [_StencilReadMask]
WriteMask [_StencilWriteMask]
}
Cull Off
Lighting Off
ZWrite Off
ZTest [unity_GUIZTestMode]
Blend One OneMinusSrcAlpha
ColorMask [_ColorMask]
Pass
{
Name "Default"
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma target 2.0
#include "UnityCG.cginc"
#include "UnityUI.cginc"
#pragma multi_compile_local _ UNITY_UI_CLIP_RECT
#pragma multi_compile_local _ 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;
half4 mask : TEXCOORD2;
float4 projPos: TEXCOORD3;
UNITY_VERTEX_OUTPUT_STEREO
};
sampler2D _MainTex;
fixed4 _Color;
fixed4 _TextureSampleAdd;
float4 _ClipRect;
float4 _MainTex_ST;
float _UIMaskSoftnessX;
float _UIMaskSoftnessY;
sampler2D _BlurTexture;
v2f vert(appdata_t v)
{
v2f OUT;
UNITY_SETUP_INSTANCE_ID(v);
UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
float4 vPosition = UnityObjectToClipPos(v.vertex);
OUT.worldPosition = v.vertex;
OUT.vertex = vPosition;
OUT.projPos = ComputeScreenPos( vPosition);
float2 pixelSize = vPosition.w;
pixelSize /= float2(1, 1) * abs(mul((float2x2)UNITY_MATRIX_P, _ScreenParams.xy));
float4 clampedRect = clamp(_ClipRect, -2e10, 2e10);
float2 maskUV = (v.vertex.xy - clampedRect.xy) / (clampedRect.zw - clampedRect.xy);
OUT.texcoord = TRANSFORM_TEX(v.texcoord.xy, _MainTex);
OUT.mask = half4(v.vertex.xy * 2 - clampedRect.xy - clampedRect.zw, 0.25 / (0.25 * half2(_UIMaskSoftnessX, _UIMaskSoftnessY) + abs(pixelSize.xy)));
OUT.color = v.color * _Color;
return OUT;
}
fixed4 frag(v2f IN) : SV_Target
{
half4 texColor = tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd;
half4 color = IN.color * texColor;
#ifdef UNITY_UI_CLIP_RECT
half2 m = saturate((_ClipRect.zw - _ClipRect.xy - abs(IN.mask.xy)) * IN.mask.zw);
color.a *= m.x * m.y;
#endif
#ifdef UNITY_UI_ALPHACLIP
clip (color.a - 0.001);
#endif
// color.rgb *= color.a;
float2 screenUV = (IN.projPos.xy / IN.projPos.w);
half4 blurMap = tex2D(_BlurTexture, screenUV);
half3 c = blurMap.rgb * blurMap.a ;// color.rgb; //加上 rgb相当于使用默认的图片进行模糊，不加相当于只模糊
half4 finalColor = float4(c, blurMap.a + (1- blurMap.a)*color.a);//blurMap的alpha值为0的时候表示不使用ui模糊
return finalColor;
}
ENDCG
}
}
}