Novice Shader Question

Unity Engine
, , ,
2

…for anybody else who ends up here - what you want to do is use ComputeGrabScreenPos to get the correct coordinates to sample the depth texture.

Here are a couple of links that helped me.

and the shader code I used that produced the result I wanted.

Shader "Unlit/DepthShade"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 grabPos : TEXCOORD1;
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            sampler2D _CameraDepthTexture;
            float4 _CameraDepthTexture_ST;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
               
                o.grabPos = ComputeGrabScreenPos(o.vertex);

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col = tex2Dproj(_CameraDepthTexture, i.grabPos);
               
                return col.r;
            }
            ENDCG
        }
    }
}