1.Shader在什么情况下使用

Self-Illumin(自身照明)，即自发光材质，乍看一下这玩意还真不太熟，仔细研究了下源码发现其实也就是最简单的颜色混合。本系列主要是针对不愿意用光照的系统自行发光，通过光照贴图来渲染颜色，这样可以避免复杂的光照困扰。

2.Shader的价值(用的多不多)，Shader的难度

个人几乎没见过用官方的这个shader，难度低。

3.代码详细注释

Shader "Legacy Shaders/Self-Illumin/Bumped Diffuse" {Properties {_Color ("Main Color", Color) = (1,1,1,1)_MainTex ("Base (RGB)", 2D) = "white" {}_Illum ("Illumin (A)", 2D) = "white" {}_BumpMap ("Normalmap", 2D) = "bump" {}_Emission ("Emission (Lightmapper)", Float) = 1.0}CGINCLUDEsampler2D _MainTex;sampler2D _BumpMap;sampler2D _Illum;fixed4 _Color;fixed _Emission;struct Input {float2 uv_MainTex;float2 uv_Illum;float2 uv_BumpMap;};void surf (Input IN, inout SurfaceOutput o) {//主纹理采样fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);//混合_Colorfixed4 c = tex * _Color;//设置Albedo颜色o.Albedo = c.rgb;//自发光颜色由纹理颜色和_Illum采样颜色的a通道混合o.Emission = c.rgb * tex2D(_Illum, IN.uv_Illum).a;//主要用于meta pass，用于烘焙Lightmap//详细看这篇https://blog.csdn.net/u012871784/article/details/81179432#if defined (UNITY_PASS_META)//让自发光的强度与_Emission做倍率乘法o.Emission *= _Emission.rrr;#endifo.Alpha = c.a;o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));}ENDCG//两个SubShader按顺序执行，执行成功则后面的不执行，适配低端机型SubShader {Tags { "RenderType"="Opaque" }LOD 300CGPROGRAM#pragma surface surf Lambert#pragma target 3.0ENDCG}SubShader {Tags { "RenderType"="Opaque" }LOD 300CGPROGRAM#pragma surface surf Lambert nodynlightmap //禁用动态光照贴图ENDCG}FallBack "Legacy Shaders/Self-Illumin/Diffuse"//详细看这篇https://blog.csdn.net/u012871784/article/details/81179432CustomEditor "LegacyIlluminShaderGUI"
}

4.Shader编写思路，用到的知识点

本系列烘焙的部分其实还比较复杂，可以看这篇