第1篇初始庐山真面目 - unity 3D Shader - Unity 3D ShaderLab开发实践

2 Unity中Shader的形态

2.1 shader基本结构

Shader "Examples/ShaderSyntax"
{
    CustomEditor = "ExampleCustomEditor"

    Properties
    {
        // Material property declarations go here
        //[optional: attribute] name("display text in Inspector", type name) = default value
    }
    SubShader
    {
        // The code that defines the rest of the SubShader goes here
        //<optional: LOD>
        //<optional: tags>
        //<optional: commands>
        //<One or more Pass definitions>
        Tags { "ExampleSubShaderTagKey" = "ExampleSubShaderTagValue" }
        LOD 100

        Pass
        {
            //<optional: name>
			//<optional: tags>
		    //<optional: commands>
   			//<optional: shader code>
           // The code that defines the Pass goes here
           Name "ExamplePassName"
           Tags { "ExamplePassTagKey" = "ExamplePassTagValue" }
           // ShaderLab commands that apply to this Pass go here.

           // HLSL code goes here.
        }
        
        Pass
        {
        	// The next pass
        }
    }

    Fallback "ExampleFallbackShader"
}

Shader包含：

关于自己的信息；
可选的fallback的shader对象；
一个或多个subshader

subshader，不同的subshader可以用来针对不同的GPU设置，不同的硬件，不同的渲染管线，和不同的运行时设置，一个subshader，为了获取想要的渲染效果定制的一个完整的渲染过程，包含：

基本信息，包括硬件，渲染管线，运行时信息；
关于subshader的key-value pair信息；
一个或多个passes；

passes，一个pass指的是一次操作得到一次绘制结果的过程，就好比执行了一次顶点着色器，片段着色器，并输出了一张绘制结果，SubShader下的Pass会按照从上往下的顺序依次渲染。pass中包含：

关于pass的key-value tag信息；
shader programs前需要设定的render state；
shader programs；

2.3 Unity中shader的2中形态

2.3.1 vertex+fragment shader

需要实现顶点和片段着色器，可以定制平台编译目标相关的参数。

2.3.2 Surface Shader

编写与光照交互的着色器很复杂。有不同的灯光类型，不同的阴影选项，不同的渲染路径（前向和延迟渲染），着色器应该以某种方式处理所有这些复杂性。

SurfaceOutput的结果如下：

struct SurfaceOutput {
	half3 Albedo; //颜色纹理
	half3 Normal; //法线，tangent space空间
	half3 Emission; //自发光，不受照明的影响
	half Specular; //高光指数，0..1范围
	half Gloss; //光泽度
	half Alpha; //Alpha通道
};

此处需要注意的是SurfaceShader中，支持的自定的函数常见的有：

#pragma surface surfaceFunction lightModel vertex:vert finalcolor:colorFunc

surfaceFunction对应的是surface函数，lightModel对应的是光照模型的函数（内置的有Standard ，StandardSpecular ，Lambert，BlinnPhong ），vert是自定义的顶点函数，colorFunc是自定义的最终颜色修改函数。

具体实例可以参见：Unity - Manual: Surface Shader examples (unity3d.com)

参见：Unity Shader - Writing Surface Shaders 编写表面着色器_Jave.Lin 的学习笔记-CSDN博客

2.4 属性和uniform变量

// in property
_MyColor ("Some Color", Color) = (1,1,1,1) 
_MyVector ("Some Vector", Vector) = (0,0,0,0) 
_MyFloat ("My float", Float) = 0.5 
_MyTexture ("Texture", 2D) = "white" {} 
_MyCubemap ("Cubemap", CUBE) = "" {}

// in hlsl
fixed4 _MyColor; // low precision type is usually enough for colors
float4 _MyVector;
float _MyFloat; 
sampler2D _MyTexture;
samplerCUBE _MyCubemap;

Properties支持的类型

Type	Example syntax	Comment
Integer	`_ExampleName ("Integer display name", Integer) = 1`	This type is backed by a real integer (unlike the legacy `Int` type described below, which is backed by a float). Use this instead of Int when you want to use an integer.
Int (legacy)	`_ExampleName ("Int display name", Int) = 1`	Note: This legacy type is backed by a float, rather than an integer. It is supported for backwards compatibility reasons only. Use the `Integer` type instead.
Float	`_ExampleName ("Float display name", Float) = 0.5` `_ExampleName ("Float with range", Range(0.0, 1.0)) = 0.5`	The maximum and minimum values for the range slider are inclusive.
Texture2D	`_ExampleName ("Texture2D display name", 2D) = "" {}` `_ExampleName ("Texture2D display name", 2D) = "red" {}`	Put the following values in the default value string to use one of Unity’s built-in textures: “white” (RGBA: 1,1,1,1), “black” (RGBA: 0,0,0,1), “gray” (RGBA: 0.5,0.5,0.5,1), “bump” (RGBA: 0.5,0.5,1,0.5) or “red” (RGBA: 1,0,0,1). If you leave the string empty or enter an invalid value, it defaults to “gray”. Note: these default textures are not visible in the Inspector.
Texture2DArray	`_ExampleName ("Texture2DArray display name", 2DArray) = "" {}`	For more information, see Texture arrays.
Texture3D	`_ExampleName ("Texture3D", 3D) = "" {}`	The default value is a “gray” (RGBA: 0.5,0.5,0.5,1) texture.
Cubemap	`_ExampleName ("Cubemap", Cube) = "" {}`	The default value is a “gray” (RGBA: 0.5,0.5,0.5,1) texture.
CubemapArray	`_ExampleName ("CubemapArray", CubeArray) = "" {}`	See Cubemap arrays.
Color	`_ExampleName("Example color", Color) = (.25, .5, .5, 1)`	This maps to a float4 in your shader code. The Material Inspector displays a color picker. If you would rather edit the values as four individual floats, use the Vector type.
Vector	`_ExampleName ("Example vector", Vector) = (.25, .5, .5, 1)`	This maps to a float4 in your shader code. The Material Inspector displays four individual float fields. If you would rather edit the values using a color picker, use the Color type.