// 當物體被遮擋之後，會在牆的一側顯示輪廓的透視效果
Shader "Custom/SeeThroughWall"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        // 透過牆看到的物體的輪廓高亮顏色
        _EdgeColor("Edge Color", Color) = (1,1,1,1)
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }

        // 顯示輪廓高亮
        Pass
        {
            // 深度測試的時候如果深度比其他物體大（被遮擋）
 

            // 渲染高亮輪廓
            ZTest Greater
            Blend One One

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag


            #include "UnityCG.cginc"

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

                //@add
 

                float3 normal : NORMAL;

            };

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

                //@add
                float3 normal : NORMAL;
                float3 viewDir : TEXCOORD1;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float4 _EdgeColor;

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

                //@add
 

                o.normal = UnityObjectToWorldNormal(v.normal);
                o.viewDir = normalize(_WorldSpaceCameraPos.xyz - mul(unity_ObjectToWorld, v.vertex).xyz);

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float NdotV = 1 - dot(i.normal, i.viewDir) * 1.5;
                return _EdgeColor * NdotV;
            }
            ENDCG
        }

        // 繪製物體
        Pass
        {
            ZTest Less 

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag


            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

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

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                return col;
            }
            ENDCG
        }
    }
}