Shader "Hidden/NimbleFox/DepthToGrayscale"
{
    SubShader
    {
        Cull Off
        ZWrite Off
        ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #include "UnityCG.cginc"

            UNITY_DECLARE_DEPTH_TEXTURE(_MainTex);

            float _DepthRangeNear;
            float _DepthRangeFar;

            fixed4 frag(v2f_img i) : SV_Target
            {
                float rawDepth = SAMPLE_DEPTH_TEXTURE(_MainTex, i.uv);
                float linearDepth = LinearEyeDepth(rawDepth);
                float normalizedDepth = saturate((linearDepth - _DepthRangeNear) / max(0.0001, _DepthRangeFar - _DepthRangeNear));
                float grayscale = 1.0 - normalizedDepth;
                return fixed4(grayscale, grayscale, grayscale, 1.0);
            }
            ENDCG
        }
    }

    Fallback Off
}