回顾：
回顾Unity中，数据的传递及Shader的工作原理：
从上图我们可以看出，在渲染管线中，顶点着色器输入的数据经过顶点着色器后，顶点着色器会把相关数据传递给片段着色器，上图即表明了在Unity的顶点着色器和片段着色器中数据的传递类型和传递方向。
/*
齐次坐标表示是计算机图形学的重要手段之一，它既能够用来明确区分向量和点
同时也更易用于进行仿射（线性）几何变换。
*/
Shader "Custom/004_RGBCube" {
SubShader {
Pass {
CGPROGRAM
#pragma vertex vert // vert function is the vertex shader
#pragma fragment frag // frag function is the fragment shader
// for multiple vertex output parameters an output structure
// is defined:
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : TEXCOORD0;
};
//POSITION语意用于顶点着色器，用来指定这些个位置坐标值，是在变换前的顶点的object space坐标。
//SV_POSITION语意则用于像素着色器，用来标识经过顶点着色器变换之后的顶点坐标。
vertexOutput vert(float4 vertexPos : POSITION)
// vertex shader
{
vertexOutput output; // we don't need to type 'struct' here
output.pos = mul(UNITY_MATRIX_MVP, vertexPos);
output.col = vertexPos + float4(0.5, 0.5, 0.5, 0.0);
// Here the vertex shader writes output data
// to the output structure. We add 0.5 to the
// x, y, and z coordinates, because the
// coordinates of the cube are between -0.5 and
// 0.5 but we need them between 0.0 and 1.0.
return output;
}
float4 frag(vertexOutput input) : COLOR // fragment shader
{
return input.col;
// Here the fragment shader returns the "col" input
// parameter with semantic TEXCOORD0 as nameless
// output parameter with semantic COLOR.
}
ENDCG
}
}
}
ShaderBuilt-in Vertex Input：
我们知道Unity Shader编程中，可以使用结构体来把顶点输入数据，如上面的示例，其实在Unity Shader编程中，有很多内建的结构体可以让我们很方便的使用，下面使用Unity内建的结构体实现上面的示例：
Shader "Custom/005_Build_InShader" {
SubShader {
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : TEXCOORD0;
};
vertexOutput vert(appdata_full input)
{
vertexOutput output;
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
output.col = input.texcoord;
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
}
}
/*
struct vertexInput {
float4 vertex : POSITION; // position (in object coordinates,
// i.e. local or model coordinates)
float4 tangent : TANGENT;
// vector orthogonal to the surface normal
float3 normal : NORMAL; // surface normal vector (in object
// coordinates; usually normalized to unit length)
float4 texcoord : TEXCOORD0; // 0th set of texture
// coordinates (a.k.a. “UV”; between 0 and 1)
float4 texcoord1 : TEXCOORD1; // 1st set of tex. coors.
float4 texcoord2 : TEXCOORD2; // 2nd set of tex. coors.
float4 texcoord3 : TEXCOORD3; // 3rd set of tex. coors.
fixed4 color : COLOR; // color (usually constant)
};
预定义结构体：
pre-defined input structures appdata_base, appdata_tan, appdata_full
and appdata_img for the most common cases.
These are defined in the file UnityCG.cginc
(in the directory Unity > Editor > Data > CGIncludes):
struct appdata_base {
float4 vertex : POSITION;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
};
struct appdata_tan {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
};
struct appdata_full {
float4 vertex : POSITION;
float4 tangent : TANGENT;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
float4 texcoord1 : TEXCOORD1;
float4 texcoord2 : TEXCOORD2;
float4 texcoord3 : TEXCOORD3;
fixed4 color : COLOR;
// and additional texture coordinates only on XBOX360
};
struct appdata_img {
float4 vertex : POSITION;
half2 texcoord : TEXCOORD0;
};
*/
uniform：
uniform变量一般用来表示：变换矩阵，材质，光照参数和颜色等信息。
Shader "Custom/006_Uniforms" {
SubShader {
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// uniform float4x4 _Object2World;
// automatic definition of a Unity-specific uniform parameter
struct vertexInput {
float4 vertex : POSITION;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 position_in_world_space : TEXCOORD0;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
output.position_in_world_space =
mul(_Object2World, input.vertex);
// transformation of input.vertex from object
// coordinates to world coordinates;
return output;
}
float4 frag(vertexOutput input) : COLOR
{
float dist = distance(input.position_in_world_space,
float4(0.0, 0.0, 0.0, 1.0));
// computes the distance between the fragment position
// and the origin (the 4th coordinate should always be
// 1 for points).
if (dist < 5.0)
{
return float4(0.0, 1.0, 0.0, 1.0);
// color near origin
}
else
{
return float4(0.1, 0.1, 0.1, 1.0);
// color far from origin
}
}
ENDCG
}
}
}
/*
uniform float4 _Time, _SinTime, _CosTime; // time values
uniform float4 _ProjectionParams;
// x = 1 or -1 (-1 if projection is flipped)
// y = near plane; z = far plane; w = 1/far plane
uniform float4 _ScreenParams;
// x = width; y = height; z = 1 + 1/width; w = 1 + 1/height
uniform float3 _WorldSpaceCameraPos;
uniform float4x4 _Object2World; // model matrix
uniform float4x4 _World2Object; // inverse model matrix
uniform float4 _WorldSpaceLightPos0;
// position or direction of light source for forward rendering
uniform float4x4 UNITY_MATRIX_MVP; // model view projection matrix
uniform float4x4 UNITY_MATRIX_MV; // model view matrix
uniform float4x4 UNITY_MATRIX_V; // view matrix
uniform float4x4 UNITY_MATRIX_P; // projection matrix
uniform float4x4 UNITY_MATRIX_VP; // view projection matrix
uniform float4x4 UNITY_MATRIX_T_MV;
// transpose of model view matrix
uniform float4x4 UNITY_MATRIX_IT_MV;
// transpose of the inverse model view matrix
uniform float4 UNITY_LIGHTMODEL_AMBIENT; // ambient color
*/
Uniform应用的第二个示例：
Shader "Custom/007_UserSpecifiedUniforms" {
Properties {
_Point ("a point in world space", Vector) = (0., 0., 0., 1.0)
_DistanceNear ("threshold distance", Float) = 5.0
_ColorNear ("color near to point", Color) = (0.0, 1.0, 0.0, 1.0)
_ColorFar ("color far from point", Color) = (0.3, 0.3, 0.3, 1.0)
}
SubShader {
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
// defines _Object2World and _World2Object
// uniforms corresponding to properties
uniform float4 _Point;
uniform float _DistanceNear;
uniform float4 _ColorNear;
uniform float4 _ColorFar;
struct vertexInput {
float4 vertex : POSITION;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 position_in_world_space : TEXCOORD0;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
output.position_in_world_space =
mul(_Object2World, input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
float dist = distance(input.position_in_world_space,
_Point);
// computes the distance between the fragment position
// and the position _Point.
if (dist < _DistanceNear)
{
return _ColorNear;
}
else
{
return _ColorFar;
}
}
ENDCG
}
}
}
/*
Shader的属性可以在脚本中被使用：
eg：
GetComponent(Renderer).sharedMaterial.SetVector("_Point",
Vector4(1.0, 0.0, 0.0, 1.0));
GetComponent(Renderer).sharedMaterial.SetFloat("_DistanceNear",
10.0);
GetComponent(Renderer).sharedMaterial.SetColor("_ColorNear",
Color(1.0, 0.0, 0.0));
GetComponent(Renderer).sharedMaterial.SetColor("_ColorFar",
Color(1.0, 1.0, 1.0));
*/
这样，我们可以通过持有属性来达到修改的目的。
Pass（通道）：RenderSetup+固定功能着色器命令
Unity中一个SubShader（渲染方案）是由一个个Pass块来执行的。每个Pass都会消耗对应的一个DrawCall。在满足渲染效果的情况下尽可能地减少Pass的数量。
Pass（通道编程）
1个Pass块可以使一个几何物体被一次渲染。
Pass { [Name and Tags] [RenderSetup] [TextureSetup] }
最基础的pass命令包含有1个可选的渲染设置命令列表，及1个可选的可用纹理列表。
一个Pass 可以定义它的名字和任意数量的标签-name/value 字符串 将Pass的含义告诉给渲染引擎。
Render Setup 渲染设置
Pass设置了一系列的显卡状态，比如说alpha混合是否开启，是否允许雾化等等。 这些命令有：
①Color color
Shader "Custom/NewShader" {
SubShader {
Pass { Color (1,0,0,0) } //将对象设置为固体颜色
}
}
②Material {Material Block} 定义一个使用顶点光照管线的材质
Shader "Custom/NewShader" {
SubShader {
Pass {
Material { //材质块用于定义对象的材质属性
Diffuse (1,1,1,1)
Ambient (1,1,1,1)
}
Lighting On
}
}
}
③Lighting On|Off 开启或关闭顶点光照
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", COLOR) = (1,1,1,1)
}
SubShader {
Pass {
Material {
Diffuse [_Color]
Ambient [_Color]
}
Lighting On
//对于在材质块中定义的设置有任何影响，您必须启用灯光与灯光的命令。如果灯光是关闭的，颜色是直接从颜色命令。
}
}
}
| ④SeparateSpecular On | Off 此命令使镜面照明添加到着色通道的末端，所以镜面照明不受纹理的影响。 |
⑤ColorMaterial AmbientAndDiffuse|Emission 使用每个顶点颜色代替材质中设置的颜色。
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", Color) = (1,1,1,0)
_SpecColor ("Spec Color", Color) = (1,1,1,1)
_Emission ("Emmisive Color", Color) = (0,0,0,0)
_Shininess ("Shininess", Range (0.01, 1)) = 0.7
_MainTex ("Base (RGB)", 2D) = "white" {}
}
SubShader {
Pass {
Material {
Diffuse [_Color]//Diffuse color: 漫反射颜色分量。这是一个对象的基本颜色。
Ambient [_Color]//Ambient color: 环境颜色分量。这是对象的颜色，在照明窗口中被环境光照射
Shininess [_Shininess]//Shininess number: 突出的清晰度，在1和0之间
Specular [_SpecColor]//Specular color: 对象的高光的颜色
Emission [_Emission]//Emission color: 物体不被任何光线击中时的颜色
}
Lighting On
SeparateSpecular On
SetTexture [_MainTex] {
Combine texture * primary DOUBLE, texture * primary
}
}
}
}
⑥Cull Back|Front|Off 设置多边形剔除模式，控制多边形应该剔除(不绘制)的面
Shader "Custom/NewShader" { //对象只渲染对象的背面
SubShader {
Pass {
Material {
Diffuse (1,1,1,1)
}
Lighting On
Cull Front
}
}
}
⑦ZWrite On|Off 设置深度写模式，控制像素从这个对象是否写入深度缓冲
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
}
SubShader {
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
LOD 200
// extra pass that renders to depth buffer only
Pass {
ZWrite On // 开启深度缓冲写
ColorMask 0 //关闭所有渲染染色通道
}
// paste in forward rendering passes from Transparent/Diffuse
UsePass "Transparent/Diffuse/FORWARD"
}
//Fallback "Transparent/VertexLit"
}
| ⑧ZTest Less | Greater | LEqual | GEqual | Equal | NotEqual | Always 设置深度测试模式 |
⑨Offset Factor, Units 允许您指定两个参数的深度偏移量
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", Color) = (1,1,1,0)
_SpecColor ("Spec Color", Color) = (1,1,1,1)
_Emission ("Emmisive Color", Color) = (0,0,0,0)
_Shininess ("Shininess", Range (0.01, 1)) = 0.7
_MainTex ("Base (RGB)", 2D) = "white" { }
}
SubShader {
// We use the material in many passes by defining them in the subshader.
// Anything defined here becomes default values for all contained passes.
Material {
Diffuse [_Color]
Ambient [_Color]
Shininess [_Shininess]
Specular [_SpecColor]
Emission [_Emission]
}
Lighting On
SeparateSpecular On
// Set up alpha blending
Blend SrcAlpha OneMinusSrcAlpha
// Render the back facing parts of the object.
// If the object is convex, these will always be further away
// than the front-faces.
Pass {
Cull Front
SetTexture [_MainTex] {
Combine Primary * Texture
}
}
// Render the parts of the object facing us.
// If the object is convex, these will be closer than the
// back-faces.
Pass {
Cull Back
SetTexture [_MainTex] {
Combine Primary * Texture
}
}
}
}
⑩SetTexture [TextureName] {Texture Block}
Shader "Custom/NewShader" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" { }
}
SubShader {
// Render the front-facing parts of the object.
// We use a simple white material, and apply the main texture.
Pass {
Material {
Diffuse (1,1,1,1)
}
Lighting On
SetTexture [_MainTex] {
Combine Primary * Texture
}
}
// Now we render the back-facing triangles in the most
// irritating color in the world: BRIGHT PINK!
Pass {
Color (1,0,1,1)
Cull Front
}
}
}
//传统的纹理合成
//Previous 是之前SetTexture的结果。
//Primary 是从照明计算或顶点颜色的颜色。
//Texture 纹理是在SetTexture TextureName指定纹理的颜色（见上图）。
//Constant 是ConstantColor指定的颜色。
⑪SetTexture [_MainTex] { combine previous * texture, previous + texture }
⑫Fog {Fog Commands} 设置雾参数
| ⑬Mode Off | Global | Linear | Exp | Exp2 |
⑭Color ColorValue
⑮Density FloatValue
⑯Range FloatValue, FloatValue
⑰AlphaTest Off 开启alpha测试
⑱AlphaTest comparison AlphaValue
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", Color) = (.5, .5, .5, .5)
_MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
_Cutoff ("Base Alpha cutoff", Range (0,.9)) = .5
}
SubShader {
// Set up basic lighting
Material {
Diffuse [_Color]
Ambient [_Color]
}
Lighting On
// Render both front and back facing polygons.
Cull Off
// first pass:
// render any pixels that are more than [_Cutoff] opaque
Pass {
AlphaTest Greater [_Cutoff]
SetTexture [_MainTex] {
combine texture * primary, texture
}
}
// Second pass:
// render in the semitransparent details.
Pass {
// Dont write to the depth buffer
ZWrite off
// Don't write pixels we have already written.
ZTest Less
// Only render pixels less or equal to the value
AlphaTest LEqual [_Cutoff]
// Set up alpha blending
Blend SrcAlpha OneMinusSrcAlpha
SetTexture [_MainTex] {
combine texture * primary, texture
}
}
}
}
⑲Blend Off 设置α混合模式
Blend SrcFactor DstFactor
Blend SrcFactor DstFactor, SrcFactorA DstFactorA
BlendOp BlendOp
Shader "Custom/NewShader" {
Properties {
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Base (RGB) Transparency (A)", 2D) = "white" {}
_Reflections ("Base (RGB) Gloss (A)", Cube) = "skybox" { TexGen CubeReflect }
}
SubShader {
Tags { "Queue" = "Transparent" }
Pass {
Blend SrcAlpha OneMinusSrcAlpha
Material {
Diffuse [_Color]
}
Lighting On
SetTexture [_MainTex] {
combine texture * primary double, texture * primary
}
}
Pass {
Blend One One
Material {
Diffuse [_Color]
}
Lighting On
SetTexture [_Reflections] {
combine texture
Matrix [_Reflection]
}
}
}
}
Per-pixel Lighting 逐像素光照
逐像素光照管道的工作依赖于渲染对象在多个pass中。Unity3D一旦获得环境光和任何顶点的光照就开始渲染物体。然后，它在一个单独添加的pass中影响渲染的物体每1个光照的像素。
Per-vertex Lighting 逐顶点光照
逐顶点光照是Direct3d/OpenGl的标准光照模式，它的计算依赖于每一个顶点。打开光照后才能启动逐顶点光照。光照受Materialblock, ColorMaterial 和 SeparateSpecular命令影响。
有几个特殊的pass可以重用公共的功能或实现一些高级效果。
UsePass 包含从另外的Shader中已被命名的pass。
GrabPass 抓取屏幕内容并转换成纹理，可以给之后的pass使用，用来做特效最好了。