Shader "Custom/DepthShader" 
{
 Properties
 {        
 }    
    
 SubShader
 {
  Tags { "RenderType" = "Opaque" }
  Pass
  {
   CGPROGRAM
   #pragma vertex vert
   #pragma fragment frag
   #pragma target 3.0
   #pragma only_renderers d3d11
   #include "UnityCG.cginc"
   static const float3 FIXED_CAM_POS = float3(0, 11.54701, 0);
   static const float SCALEFACTOR = 100;
   struct appdata
   {
    float4 vertex : POSITION;
   };
   struct v2f
   {
    float4 vertex: SV_POSITION;
    float3 worldPos: TEXCOORD0;
   };
        
   v2f vert(appdata v)
   {
    v2f o;
    o.vertex = UnityObjectToClipPos(v.vertex);                
    o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
    return o;
   }
   float4 frag(v2f i) : SV_Target
   {
    // Distance from current (fixed) cam pos to pixel world pos
    float3 vDist = i.worldPos - FIXED_CAM_POS;
    // Only considering distance in YZ-plane and scaling
    float Dist = length(float3(0, vDist.y, vDist.z)) / SCALEFACTOR;
    return(EncodeFloatRGBA(Dist));
   }
   ENDCG
  }
 }    
}

Shader "Custom/SceneShader" 
{
 Properties
 {
  _MainTex("MainTexture", 2D) = "white" {}
  _DepthTex("DepthTexture", 2D) = "white" {}
 }
 SubShader
 {
  Tags { "RenderType" = "Opaque" }
  Tags {"LightMode" = "ForwardBase"}
  Pass
  {
   CGPROGRAM
   #pragma vertex vert
   #pragma fragment frag
   #pragma target 3.0
   #pragma only_renderers d3d11
   #include "UnityCG.cginc"
   #include "UnityLightingCommon.cginc"
        
   static const float3 FIXED_CAM_POS = float3(0, 11.54701, 0);
   static const float SCALEFACTOR = 100;
   static const float TAN30DEG = 0.57735026918962576450914878050196;
   static const float WORLDPOS_X_OFFS = 10;
   static const float WORLDPOS_Y_OFFS =  0;
   static const float WORLDPOS_X_SIZE = 20;
   static const float WORLDPOS_Y_SIZE = 40;
   struct appdata
   {
    float4 vertex : POSITION;
    float3 normal : NORMAL;
    float2 uv : TEXCOORD0;
    fixed3 color : COLOR0;
   };
   struct v2f
   {
    float4 vertex : SV_POSITION;
    float2 uv : TEXCOORD0;
    float3 worldPos : TEXCOORD1;
    float4 diffuse : COLOR0;
   };
   sampler2D _MainTex;
   float4 _MainTex_ST;
            
   sampler2D_float _DepthTex;
   float4 _DepthTex_ST;
                
  v2f vert(appdata v)
  {
   v2f o;
   o.vertex = UnityObjectToClipPos(v.vertex);
   o.uv = TRANSFORM_TEX(v.uv, _MainTex);
   o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
   // Simple lighting
   half3 worldNormal = UnityObjectToWorldNormal(v.normal);
   half nl = max(0, dot(worldNormal, _WorldSpaceLightPos0.xyz));
   o.diffuse = nl * _LightColor0;
   return o;
  }
            
  float4 frag(v2f i) : SV_Target
  {    
   i.uv = float2(1,1) - i.uv;
   float4 colObj = tex2D(_MainTex, i.uv) * i.diffuse;
   float2 DepthUV = (i.worldPos.xz + float2(WORLDPOS_X_OFFS, WORLDPOS_Y_OFFS));
   DepthUV /= float2(WORLDPOS_X_SIZE, WORLDPOS_Y_SIZE);
   DepthUV.y += (i.worldPos.y / TAN30DEG / WORLDPOS_Y_SIZE);
                
   float DistOld = DecodeFloatRGBA(tex2D(_DepthTex, DepthUV)) * SCALEFACTOR;
   float3 vDistNew = i.worldPos - FIXED_CAM_POS;
   float DistNew = length(float3(0, vDistNew.y, vDistNew.z));
                
   if (DistNew > DistOld) discard;
   return(colObj);
   }
   ENDCG
  }
 }
}