decal in unity

// Upgrade NOTE: commented out 'float4x4 _CameraToWorld', a built-in variable
// Upgrade NOTE: replaced '_CameraToWorld' with 'unity_CameraToWorld'
// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced '_World2Object' with 'unity_WorldToObject'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

// http://www.popekim.com/2012/10/siggraph-2012-screen-space-decals-in.html

Shader "Decal/DecalShader Diffuse+Normals"
{
Properties
{
_MainTex ("Diffuse", 2D) = "white" {}
_BumpMap ("Normals", 2D) = "bump" {}
}
SubShader
{
Pass
{
Fog { Mode Off } // no fog in g-buffers pass
ZWrite Off
//Blend SrcAlpha OneMinusSrcAlpha

CGPROGRAM
#pragma target 3.0
#pragma vertex vert
#pragma fragment frag
#pragma exclude_renderers nomrt

#include "UnityCG.cginc"

struct v2f
{
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
float4 screenUV : TEXCOORD1;
float3 ray : TEXCOORD2;
half3 orientation : TEXCOORD3;
half3 orientationX : TEXCOORD4;
half3 orientationZ : TEXCOORD5;
};

v2f vert (float3 v : POSITION)
{
v2f o;
o.pos = UnityObjectToClipPos (float4(v,1));
o.uv = v.xz+0.5;
o.screenUV = ComputeScreenPos (o.pos);
o.ray = mul (UNITY_MATRIX_MV, float4(v,1)).xyz * float3(-1,-1,1);
o.orientation = mul ((float3x3)unity_ObjectToWorld, float3(0,1,0));
o.orientationX = mul ((float3x3)unity_ObjectToWorld, float3(1,0,0));
o.orientationZ = mul ((float3x3)unity_ObjectToWorld, float3(0,0,1));
return o;
}

CBUFFER_START(UnityPerCamera2)
// float4x4 _CameraToWorld;
CBUFFER_END

sampler2D _MainTex;
sampler2D _BumpMap;
sampler2D_float _CameraDepthTexture;
sampler2D _NormalsCopy;

void frag(v2f i, out half4 outDiffuse : COLOR0, out half4 outNormal : COLOR1)
{
i.ray = i.ray * (_ProjectionParams.z / i.ray.z);
float2 uv = i.screenUV.xy / i.screenUV.w;
// read depth and reconstruct world position
float depth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, uv);
depth = Linear01Depth (depth);
float4 vpos = float4(i.ray * depth,1);
float3 wpos = mul (unity_CameraToWorld, vpos).xyz;
float3 opos = mul (unity_WorldToObject, float4(wpos,1)).xyz;

clip (float3(0.5,0.5,0.5) - abs(opos.xyz));

i.uv = opos.xz+0.5;

half3 normal = tex2D(_NormalsCopy, uv).rgb;
fixed3 wnormal = normal.rgb * 2.0 - 1.0;
clip (dot(wnormal, i.orientation) - 0.3);

fixed4 col = tex2D (_MainTex, i.uv);
clip (col.a - 0.2);
outDiffuse = col;

fixed3 nor = UnpackNormal(tex2D(_BumpMap, i.uv));
half3x3 norMat = half3x3(i.orientationX, i.orientationZ, i.orientation);
nor = mul (nor, norMat);
outNormal = fixed4(nor*0.5+0.5,1);

}
ENDCG
}

}

Fallback Off
}

decal算一个uv

 这个配defferred lght的 需要全屏的depth和normal 开销很大，decalmesh需要cull不然会越来越多

https://docs.unity3d.com/Manual/GraphicsCommandBuffers.html