All shaders start with the keyword Shader followed by a string that represents the name of the shader. This is the name that is shown in the Inspector. All code for this shader must be put within the curly braces after it: { } (called a block).
所有的shaders都必须以Shader作为开始，接着是这个shader的名称(例如：VertexLit)，这个名称将会显示于检视器(Inspector)。所有的语法都必须放在{ }之内。
The name should be short and descriptive. It does not have to match the .shader file name.
这个名称必须短且足以代表其功能，它并不会等于.shader的档案名称
To put shaders in submenus in Unity, use slashes - eg MyShaders/Test would be shown as Test in a submenu called MyShaders, or MyShaders->Test.
如果要把shaders放在unity的submenus下面，请使用斜线，例如：MyShaders/Test，你将会看到有个submenu名为MyShaders，下面有个shader名为Test，或是像这样MyShaders->Test
The shader is composed of a Properties block followed by SubShader blocks. Each of these is described in sections below.
Properties
At the beginning of the shader block you can define any properties that artists can edit in the Material Inspector. In the VertexLit example the properties look like this:
图片一
The properties are listed on separate lines within the Properties block. Each property starts with the internal name (Color, MainTex). After this in parentheses comes the name shown in the inspector and the type of the property. After that, the default value for this property is listed:
图片二
The list of possible types are in the Properties Reference. The default value depends on the property type. In the example of a color, the default value should be a four component vector.
可用的性质类型请参考Properties Reference。预设值与性质有关，以color为例，预设值应该由四个值组成
We now have our properties defined, and are ready to start writing the actual shader.
现在我们已经定义了四个性质，可以开始撰写实际的shader了
The Shader Body
Before we move on, let's define the basic s***cture of a shader file.
在开始以前，先了解shader的结构是如何定义的
Different graphic hardware has different capabilities. For example, some graphics cards support fragment programs and others don't; some can lay down four textures per pass while the others can do only two or one; etc. To allow you to make full use of whatever hardware your user has, a shader can contain multiple SubShaders. When Unity renders a shader, it will go over all subshaders and use the first one that the hardware supports.