这是使用了反射材质的水壶，模拟了金属反射室内的情况。室内用的是一个天空球模拟的。

fixed fresnel = _FresnelScale + (1 - _FresnelScale) * pow(1 - dot(worldViewDir, worldNormal), 5);

在片元着色器添加一行菲涅尔反射用的参数，然后将正常的ReflectionShader的_ReflectAmount换成新计算的fresnel，改变插值的系数。

Shader "UnityShaderLearning/Reflection"
{
    Properties
    {
        _Color ("Color Tint", Color) = (1, 1, 1, 1)
        _ReflectColor ("Reflection Color", Color) = (1, 1, 1, 1)
        _ReflectAmount ("Reflect Amount", Range(0, 1)) = 1
        _Cubemap ("Reflection Cubemap", Cube) = "_Skybox" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue"="Geometry" }
        Pass
        {
            Tags { "Lighting"="ForwardBase" }
            CGPROGRAM
            #pragma multi_compile_fwdbase
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"
            #include "AutoLight.cginc"

            fixed4 _Color;
            fixed4 _ReflectColor;
            fixed _ReflectAmount;
            samplerCUBE _Cubemap;

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

            struct v2f
            {
                float4 pos : SV_POSITION;
                fixed3 worldPos : TEXCOORD0;
                fixed3 worldNormal : TEXCOORD1;
                fixed3 worldViewDir : TEXCOORD2;
                fixed3 worldRefl : TEXCOORD3;
                SHADOW_COORDS(4)
            };

            v2f vert(a2v v)
            {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                o.worldViewDir = UnityWorldSpaceViewDir(o.worldPos);
                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 * max(0, dot(worldNormal, worldLightDir));
                fixed3 reflection = texCUBE(_Cubemap, i.worldRefl).rgb * _ReflectColor.rgb;
                UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);
                fixed3 color = ambient + lerp(diffuse, reflection, _ReflectAmount) * atten;
                return fixed4(color, 1.0);
            }
            ENDCG
        }
    }
    FallBack "Reflective/VertexLit"
}