Demo 50 - Grayscale depending ZBuffer

Shader "Custom/ZBuffer"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" }

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

            struct v2f
            {
                float4 pos : SV_POSITION;
                float4 screenuv : TEXCOORD1;
            };

            v2f vert (appdata_base v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.screenuv = ComputeScreenPos(o.pos);
                return o;
            }

            sampler2D _CameraDepthTexture;

            fixed4 frag (v2f i) : SV_Target
            {
                float2 uv = i.screenuv.xy / i.screenuv.w;
                float depth = 1 - Linear01Depth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, uv));
                return fixed4(depth, depth, depth, 1);
            }
            ENDCG
        }
    }
}