Shader "Hidden/DepthCopy"
{
    Properties
    {
        // Is not used, we only need to sample from the depth map provided by the simulator camera
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100
        Cull Off
        ZWrite Off
        ZTest Off

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

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

            sampler2D _CameraDepthTexture;

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

            float frag (v2f i) : SV_Target
            {
                // Adding small value to offset the depth to avoid occluding the meshes of simulation environments
                float depth = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, i.uv));
                return depth;
            }
            ENDCG
        }
    }
}