UnityShaderBook/Assets/Shaders/Extra/Reflect/TestReflectShader.shader

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'

Shader "Unlit/TestReflectShader"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_CubeMapRef("Reflect Cube",Cube) = "_Skybox"{}
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100

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

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float3 normal : NORMAL;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;
				float3 worldPos : TEXCOORD1;
				fixed3 worldNormal : TEXCOORD2;
				fixed3 worldViewDir : TEXCOORD3;
				fixed3 worldRefl : TEXCOORD4;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			samplerCUBE _CubeMapRef;
			
			v2f vert (appdata v)
			{
				v2f o;
				//从模型空间转换到裁剪空间
				o.vertex = UnityObjectToClipPos(v.vertex);
				//转换UV坐标
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				//把法线方向从模型空间转换到世界空间中
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				//o.worldNormal = UnityObjectToWorldDir(v.normal);
				//o.worldNormal = normalize(mul(unity_ObjectToWorld,v.normal));
				//顶点/方向矢量从模型空间变换到世界空间
				o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;
				//世界空间中的顶点位置->世界空间中从该点到摄像机的观察方向。
				o.worldViewDir = UnityWorldSpaceViewDir(o.worldPos);
				//反射运算
				o.worldRefl = reflect(-o.worldViewDir,o.worldNormal);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				fixed3 reflecion = texCUBE(_CubeMapRef,i.worldRefl).rgb;
				half4 skyData = UNITY_SAMPLE_TEXCUBE(unity_SpecCube0, i.worldRefl);
                // decode cubemap data into actual color
                half3 skyColor = DecodeHDR (skyData, unity_SpecCube0_HDR);
				return fixed4(skyColor,1);
			}
			ENDCG
		}
	}
}