Hi there I am trying to implement a mask using Stencil buffers in URP. I got it working in HDRP but I am unable to understand how it works in URP.
I have one shader that writes in the stencil and another one that is comparing its ref value against the writer.
The problem is that even if I have a shader that is using ref 10 (even no one is writing value 10 to the stencil buffer) it is is being renderer and I don’t understand why.
(Using Unity 6)
Code for the shader
Shader "Custom/Unlit"
{
Properties
{
_MainTex ("Texture", 2D) = "white" {}
}
SubShader
{
Tags
{
"RenderPipeline" = "UniversalRenderPipeline"
"RenderType" = "Opaque"
"Queue" = "Geometry"
}
Stencil
{
Ref 10
Comp Equal
Pass Keep
Fail Keep
ZFail Keep
}
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float2 uv : TEXCOORD0;
UNITY_FOG_COORDS(1)
float4 vertex : SV_POSITION;
};
sampler2D _MainTex;
float4 _MainTex_ST;
v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
return o;
}
fixed4 frag (v2f i) : SV_Target
{
return fixed4(0, 1, 0, 1); // Green if correct
}
ENDCG
}
}
}
I am still trying to figure out how to handle the Stencil buffer in the URP. I just noticed that the camera position is relevant. So it seems like it has something to do with the dept. Since when the camera is too far from the object the stencil buffer gets ignored. I am still don’t understand why
Those are the working Shaders in HDRP in case it helps someone
Writer shader
Shader "Suduck/StencilWritter"
{
Properties
{
_StencilMask("_StencilWriteMask", Float) = 255
}
SubShader
{
Tags { "RenderType" = "Opaque" }
Pass
{
Name "StencilWrite"
Stencil
{
Ref 64
ReadMask 192
WriteMask 192
Comp Always
Pass Replace
Fail Replace
ZFail Replace
}
ZTest Always
ZWrite Off
ColorMask 0
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float2 uv : TEXCOORD0;
UNITY_FOG_COORDS(1)
float4 vertex : SV_POSITION;
};
sampler2D _MainTex;
float4 _MainTex_ST;
v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}
fixed4 frag (v2f i) : SV_Target
{
// sample the texture
fixed4 col = tex2D(_MainTex, i.uv);
// apply fog
UNITY_APPLY_FOG(i.fogCoord, col);
return col;
}
ENDCG
}
}
FallBack Off
}
Reader shader
Shader "Custom/StencilUnit"
{
Properties
{
_Color ("Color", Color) = (1,1,1,1)
_MainTex ("Albedo (RGB)", 2D) = "white" {}
_Glossiness ("Smoothness", Range(0,1)) = 0.5
_Metallic ("Metallic", Range(0,1)) = 0.0
}
SubShader
{
Tags
{
"RenderType"="Opaque"
}
LOD 200
Pass
{
Stencil
{
Ref 64
ReadMask 192
WriteMask 192
Comp Equal
Pass Keep
}
ZTest On
ZWrite On
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float2 uv : TEXCOORD0;
UNITY_FOG_COORDS(1)
float4 vertex : SV_POSITION;
};
sampler2D _MainTex;
float4 _MainTex_ST;
v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}
fixed4 frag (v2f i) : SV_Target
{
// sample the texture
fixed4 col = tex2D(_MainTex, i.uv);
// apply fog
UNITY_APPLY_FOG(i.fogCoord, col);
return col;
}
ENDCG
}
}
}
I figure it out. The problem was that I was using Deferred rendering and the shaders act differently with the stencil buffer in that context. In my case I can render in Foward+ since I won’t have lots of lights