Demo 09 - Mask stencil

Shader "Custom/Mask" {
    SubShader {
        Tags { "RenderType"="Transparent" }
        Stencil {
            Ref 1
            Comp always
            Pass replace
        }

        CGPROGRAM
        #pragma surface surf Lambert alpha

        struct Input {
            fixed3 Albedo;
        };

        void surf (Input IN, inout SurfaceOutput o) {
            o.Albedo = fixed3(1, 1, 1);
            o.Alpha = 0;
        }
        ENDCG
    }
    FallBack "Diffuse"
}