RenderTextureSubElement.Stencil

Description

Stencil element of a render texture.

Used to access the stencil data of the underlying surface from a render texture and bind it in a shader. Make sure you set the stencilFormat of your render texture to a format supported on the target platform before it is created.

To access the stencil information in a shader, you need to read it from the correct channel. The stencil data is stored in the red channel for all graphics APIs that support it except for DirectX 11, in which case it is stored in the green channel.

If the stencilFormat is set to R8_UInt, you need to use the function Load to read from the texture. Otherwise, if the format is R8_UNorm you can use sampling.

When using MSAA render textures, you need to define the stencil texture using the equivalent MS texture types.

You cannot bind the stencil buffer as a RWTexture.

Below is an example Unlit shader that reads the stencil information from a render texture with stencilFormat R8_UInt and writes it as color information on the green channel.

See Also: GraphicsFormat.

Shader "Unlit/ExampleShader"
{
    Properties
    {
        _ExampleTex("Texture", 2D) = "" {}
    }
    SubShader
    {
        Tags { "RenderType" = "Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 4.0

            #include "UnityCG.cginc"


            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };


                    #if SHADER_API_D3D11
                    #define STENCIL_CHANNEL g
                    #else
                    #define STENCIL_CHANNEL r
                    #endif

            Texture2D<uint2> _ExampleTex;

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                int xRes = 1024;
                int yRes = 768;

                uint stencil = _ExampleTex.Load(int3(floor(i.uv.x * xRes), floor(i.uv.y * yRes), 0)).STENCIL_CHANNEL;
                fixed4 col = float4(0.0, float(stencil) / 255.0f, 0.0, 1.0);

                return col;
            }

            ENDCG
        }
    }
}