[5.10] Cube Map 연습

1. 씬의 Skybox 설정
2. Cube Property 받기
3. SamplerCUBE로 큐브 받기
4. Reflection 적용 (Input 구조체에 float3 worldRefl) => surf에서 적용 및 Input 구조체에 INTERNAL_DATA 작성
   
   1. float4 ref = texCUBE(SamplerCube, WorldReflectionVector(struct Input, float3))
5. Emission 쪽에서 출력
6. 값을 변경하며 적정값 찾기
7. Bump Map은 WorldReflectionVector에 사용되어질꺼기 때문에 먼저 선언해주어야됨.

Shader "Custom/Skybox"
{
    Properties
    {
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _BumpTex ("Albedo (RGB)", 2D) = "bump" {}
        _Cube ("Cube Map", Cube) = "" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }

        CGPROGRAM
        #pragma surface surf Lambert

        sampler2D _MainTex;
        sampler2D _BumpTex;
        samplerCUBE _Cube;

        struct Input
        {
            float2 uv_MainTex;
            float2 uv_BumpTex;
            float3 worldRefl;
            INTERNAL_DATA
        };

        void surf (Input IN, inout SurfaceOutput o)
        {
            o.Normal = UnpackNormal(tex2D(_BumpTex, IN.uv_BumpTex));
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex);

            float4 ref = texCUBE(_Cube, WorldReflectionVector(IN, o.Normal));

            o.Albedo = c.rgb * 0.9;
            o.Emission = ref.rgb;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}