菲涅耳内轮廓

使用菲涅耳公式实现内轮廓效果。

菲涅耳简化公式

$F_0为平面的基础反射率，\vec{n}为法向量，\vec{v}为视角向量。 \\ F_0+(1?F_0)(1?(\vec{n} \cdot \vec{v}))^5$
各个材质对应的反射率如下：
在这里插入图片描述

内轮廓改造菲涅耳公式

$将菲涅耳公式改为：F_0+F_1*(1-|\vec{n} \cdot \vec{v}|)^5$

实现

Shader "Unlit/Fresnel"
{
    Properties
    {
        _FresnelColor ("FresnelColor", Color) = (1, 1, 1, 1)
        _FresnelBase ("FresnelBase", Range(0, 1)) = 1
        _FresnelScale ("FresnelScale", Range(0, 1)) = 1
        _FresnelPower ("FresnelPower", Range(0, 5)) = 5
    }
    SubShader
    {
        ZWrite Off
        Cull Off
        Blend One One
        Tags { "RenderType" = "Transparent" }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 normal : TEXCOORD0;
                float3 viewDir : TEXCOORD1;
            };

            float _FresnelBase;
            float _FresnelScale;
            float _FresnelPower;
            float4 _FresnelColor;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.normal = normalize(UnityObjectToWorldDir(v.normal));
                o.viewDir = normalize(UnityWorldSpaceViewDir(mul(unity_ObjectToWorld, v.vertex)));
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                return saturate(_FresnelBase + _FresnelScale * pow(1.0 - abs(dot(i.normal, i.viewDir)), _FresnelPower)) * _FresnelColor;
            }
            ENDCG
        }
    }
}