物体边缘发光效果是游戏里面非常常用的一种效果，同样是为了凸显游戏中的某个物体。下面使用Shader实现物体的边缘内发光和外发光效果。
一、边缘内发光
原理：用视角方向和法线方向点乘，模型越边缘的地方，它的法线和视角方向越接近90度。用1减去上面点乘的结果得到的就是越边缘的地方越亮。
Shader "Custom/Outline1" {Properties{_MainTex("main tex",2D) = "black"{}_RimColor("rim color",Color) = (1,1,1,1)//边缘颜色_RimPower("rim power",range(1,10)) = 2//边缘强度}SubShader{Pass{CGPROGRAM#pragma vertex vert#pragma fragment frag#include"UnityCG.cginc"struct v2f{float4 vertex:POSITION;float4 uv:TEXCOORD0;float4 NdotV:COLOR;};sampler2D _MainTex;float4 _RimColor;float _RimPower;v2f vert(appdata_base v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.uv = v.texcoord;float3 V = WorldSpaceViewDir(v.vertex);V = mul(unity_WorldToObject,V);//视方向从世界到模型坐标系的转换o.NdotV.x = saturate(dot(v.normal,normalize(V)));//必须在同一坐标系才能正确做点乘运算return o;}half4 frag(v2f IN) :COLOR{half4 c = tex2D(_MainTex,IN.uv);//用视方向和法线方向做点乘，越边缘的地方，法线和视方向越接近90度，点乘越接近0.//用（1- 上面点乘的结果）*颜色，来反映边缘颜色情况c.rgb += pow((1 - IN.NdotV.x) ,_RimPower)* _RimColor.rgb;return c;}ENDCG}}FallBack "Diffuse"}
二、边缘外发光
原理：让物体的顶点位置沿着法线方向延伸，然后使用法线点乘物体法线的方向形成一个中间向四周扩散逐渐衰减的效果。
Shader "Custom/OutLine2" {Properties{_MainTex("Texture(RGB)",2D) = "grey"{}//主纹理_Color("Color",Color) = (0,0,0,1)//主纹理颜色_AtmoColor("Atmosphere Color",Color) = (0,0,0,0)//光晕颜色_Size("Size",Range(0,1)) = 0.1//光晕范围_OutLightPow("Falloff",Range(1,10)) = 5//光晕系数_OutLightStrength("Transparency",Range(5,20)) = 15//光晕强度}SubShader{Pass{Name "PlaneBase"Tags{"LightMode" = "Always"}Cull Back//剔除背面CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"uniform sampler2D _MainTex;uniform float4 _MainTex_ST;uniform float4 _Color;uniform float4 _AtmoColor;uniform float _Size;uniform float _OutLightPow;uniform float _OutLightStrength;struct vertexOutput {float4 pos : SV_POSITION;float3 normal : TEXCOORD0;float3 worldvertpos : TEXCOORD1;float2 texcoord : TEXCOORD2;};//顶点着色器vertexOutput vert(appdata_base v){vertexOutput o;//顶点位置o.pos = UnityObjectToClipPos(v.vertex);//法线o.normal = v.normal;//世界坐标顶点位置o.worldvertpos = mul(unity_ObjectToWorld, v.vertex).xyz;o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);return o;}float4 frag(vertexOutput i) : COLOR{float4 color = tex2D(_MainTex,i.texcoord);return color * _Color;}ENDCG}Pass{Name "AtmosphereBase"Tags{"LightMode" = "Always"}Cull FrontBlend SrcAlpha OneCGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"uniform float4 _Color;uniform float4 _AtmoColor;uniform float _Size;uniform float _OutLightPow;uniform float _OutLightStrength;struct vertexOutput{float4 pos : SV_POSITION;float3 normal : TEXCOORD0;float3 worldvertpos : TEXCOORD1;};vertexOutput vert(appdata_base v) {vertexOutput o;//顶点位置以法线方向向外延伸v.vertex.xyz += v.normal * _Size;o.pos = UnityObjectToClipPos(v.vertex);o.normal = v.normal;o.worldvertpos = mul(unity_ObjectToWorld, v.vertex);return o;}float4 frag(vertexOutput i) : COLOR{i.normal = normalize(i.normal);//视角法线float3 viewdir = normalize(i.worldvertpos.xyz - _WorldSpaceCameraPos.xyz);float4 color = _AtmoColor;//视角法线与模型法线点积形成中间为1向四周逐渐衰减为0的点积值，赋值透明通道，形成光晕效果color.a = pow(saturate(dot(viewdir, i.normal)),_OutLightPow);color.a *= _OutLightStrength * dot(viewdir, i.normal);return color;}ENDCG}}FallBack "Diffuse"}
效果图：
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