Using Alphas in a Stencil Mask

Unity Engine
1

Hi everyone, I am only really new to shaders but I have been trying to use alphas with a stencil.

Mask Script:

Shader "Custom/Stencil_Mask" {
    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" "Queue" = "Geometry-100" }
        ColorMask 0
        ZWrite off
        LOD 200

        Stencil
        {
            Ref 1
            Pass replace
        }

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input {
            float2 uv_MainTex;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

Object Shader:

Shader "Custom/Stencil_Object" {
    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

        Stencil
        {
        Ref 1
        Comp equal
        }

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input {
            float2 uv_MainTex;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

An object is given the mask shader which others are given the stencil. When the Mask object is above the Stencil objects they will become visible, otherwise they are invisible. This works well, however I want to give this a bit more customisation. At the moment the world that the mask is not covering is pitch black and the objects the mask is over are 100% visible. Is it possible to add an alpha value would allow me to find a middle ground for this?

Something like, the objects not under the mask are darker but still slightly visible rather than pitch black and completely hidden.

Any help on this would be fantastic! Cheers.

2

i’m also a bit of a newb with this, but from all the research i’ve done on a similar topic, i dont think you can alpha the stencil, or at least directly. you may be able to add a second pass with something similar to an outline shader to do what you are looking for.