1.注意OpenGL和DirectX的坐标轴：
2.部分专业名词介绍
#pragma surface surfaceFunction lightModel[optionalparams]
声称着色器 表面着色器 着色器代码名称 光照模型
It uses #pragma surface ... directive to indicate it’s a surface shader.
eg:#pragma surface surf Standard fullforwardshadows
介绍lightModel
1.Standard：
This lighting model uses SurfaceOutputStandard output struct,
and matches the Standard (metallic workflow) shader in Unity.
2.Standard：
This Specular lighting model uses SurfaceOutputStandardSpecular output struct,
and matches the Standard (specular setup) shader in Unity.
3.Lambert and BlinnPhong：郎伯模型
This lighting models are not physically based (coming from Unity 4.x),
but the shaders using them can be faster to render on low-end hardware.
3.Unity shader类型
1）Standard Surface Shader：标准光照模型
2）Standard Surface Shader（instanced）
3）Unlit Shader：不包含光照，包含雾效
4）Image Effect Shader：实现屏幕后处理效果
5）Compute Shader：产生一个特殊的shader文件，目的是利用cpu的并行性进行一些与常规渲染流水线无关·
4.Unity Shader语法