实现思路：取屏幕像素的RGB值，将三个通道的值相加，除以一个大于值使颜色值在0-1内，再乘上一个强度值调节黑白强度。
在URP中实现需要开启Opaque Texture
ShaderGraph实现：
ShaderLab实现：
Shader "BlackAndWhite"
{Properties{}SubShader{Tags { "RenderType"="Transprent" "Queue"="Geometry" }Pass{HLSLPROGRAM#pragma vertex vert#pragma fragment frag#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"TEXTURE2D_X(_CameraOpaqueTexture);SAMPLER(sampler_CameraOpaqueTexture);float3 SampleSceneColor(float2 uv){return SAMPLE_TEXTURE2D_X(_CameraOpaqueTexture, sampler_CameraOpaqueTexture, UnityStereoTransformScreenSpaceTex(uv)).rgb;}float4 ComputeScreenPos (float4 pos, float projectionSign){float4 o = pos * 0.5f;o.xy = float2(o.x, o.y * projectionSign) + o.w;o.zw = pos.zw;return o;}struct appdata{float4 vertex : POSITION;};struct v2f{float4 vertex : SV_POSITION;float4 ScreenPosition : TEXCOORD0;};v2f vert (appdata v){v2f o;o.vertex = mul(UNITY_MATRIX_MVP,v.vertex);o.ScreenPosition = ComputeScreenPos(TransformWorldToHClip(mul(unity_ObjectToWorld, v.vertex)),_ProjectionParams.x);return o;}float4 frag (v2f i) : SV_Target{float4 _ScreenPosition_Out_0 = float4(i.ScreenPosition.xy / i.ScreenPosition.w, 0, 0);float3 col = SampleSceneColor(_ScreenPosition_Out_0.xy);float c = (col.x + col.y + col.z) / 3;return float4(c,c,c,1);}ENDHLSL}}
}实现效果：
对比将物体只变成透明：
参考链接：
Black & White Shader - Unity (URP/HDRP) Shader Graph (youtube.com)