UnityShader中级篇——菲涅尔反射

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最新推荐文章于 2025-05-30 14:31:52 发布

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分类专栏： UnityShader初级篇

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本文介绍了一款基于Unity引擎的Shader，通过菲涅尔公式实现动态反射效果。该Shader结合了环境光、漫反射及菲涅尔反射，能够根据视角和表面法线的变化调整反射强度，模拟出接近真实的光学反射现象。

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// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unity Shaders Book/Chapter 10/Fresnel"
{
	Properties
	{
		_Color("Color Tint",Color) = (1,1,1,1)
        _FresnelScale("Fresnel Scale",Range(0,1)) = 0.5
		_Cubemap("Refraction Cubemap",Cube) = "_Skybox"{}
	}
		SubShader
	{
		Tags{ "RenderType" = "Opaque" "Queue" = "Geometry" }

		Pass
		{
			Tags{ "LightMode" = "ForwardBase" }

			CGPROGRAM
		//确保光源变量可以被正确赋值
        #pragma multi_compile_fwdbase

	    #pragma vertex vert
		#pragma fragment frag


		//包含引用的内置文件  
		 #include "Lighting.cginc"  
         #include "AutoLight.cginc"

		//声明properties中定义的属性  
	 fixed4 _Color;
	 fixed _FresnelScale;
	 //声明cubemap
	 samplerCUBE _Cubemap;

		struct a2v
	{
		float4 vertex : POSITION;
		float3 normal : NORMAL;
	};

	struct v2f
	{
		float4 pos : SV_POSITION;
		//存储世界坐标下的法线方向和顶点坐标  
		float3 worldNormal : TEXCOORD0;
		float3 worldPos : TEXCOORD1;
		float3 worldViewDir: TEXCOORD2;
		float3 worldRefl:TEXCOORD3;
		SHADOW_COORDS(4)
	};

			v2f vert (a2v v)
			{
				v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
				o.worldViewDir = UnityWorldSpaceViewDir(o.worldPos);
				//计算该顶点处的反射方向
				o.worldRefl = reflect(-o.worldViewDir, o.worldNormal);

				TRANSFER_SHADOW(o);

				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				fixed3 worldNormal = normalize(i.worldNormal);
			    fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
				fixed3 worldViewDir = normalize(i.worldViewDir);

				fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz;

				fixed3 diffuse = _LightColor0.rgb * _Color.rgb * saturate(dot(worldNormal, worldLightDir));

				//利用反射方向来对立方体纹理采样
				fixed3 reflection = texCUBE(_Cubemap, i.worldRefl).rgb;

				//计算菲涅尔反射
				//菲涅尔近似等式
				fixed fresnel = _FresnelScale + (1 - _FresnelScale) * pow(1 - dot(worldViewDir, worldNormal), 5);

				UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);

				//混合漫反射颜色与反射颜色
				fixed3 color = ambient + lerp(diffuse, reflection, saturate(fresnel)) * atten;

				return fixed4(color, 1.0);

			}
			ENDCG
		}
	}
		Fallback"Reflective/VertexLit"
}