arfoundation-samples/Assets/Scenes/PlaneOcclusion/PlaneOcclusionShader.shader

Shader "AR/Occlusion"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        Tags { "Queue" = "Geometry-1" }
        ZWrite On
        ZTest LEqual
        ColorMask 0

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
            };

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

            fixed4 frag (v2f i) : SV_Target
            {
                return fixed4(0.0, 0.0, 0.0, 0.0);
            }
            ENDCG
        }
    }
}