openGL shader学习总结

　　着色器是运行在GPU上的小程序，着色器是一种C风格语言——GLSL。
　　一、GLSL
　　GLSL是为图形量身定制的，它为向量和矩阵运算提供了很大帮助。
　　1、着色器的开头总是要声明版本，接着是输入和输出变量、uniform和main函数。main函数时每个着色器的入口，用于处理所有输入变量，并用输出变量输出处理结果。
　　2、类型：着色器的类型包括：int、float、double、uint、bool。GLSL的两种容器类型：向量和矩阵。
　　向量是有1、2、3或4个元素的基本类型容器。vecn：包含n个默认为float元素的向量；其他还有bvecn、ivecn、uvecn、dvecn，可以使用vec.x、.y、.z、.w来获取它们的1、2、3、4号元素，GLSL也允许使用rgba来获取颜色的元素，或者stpq获取纹理坐标元素。
　　3、in和out:着色器是各自独立的小程序，每个着色器都是用这两个关键字定义输入和输出。使用layout元数据制定输入变量，这样才可以在CPU上配置顶点属性。
　　4、定点着色器：
　　

#version 330 corelayout (location = 0) in vec3 position; // 位置变量的属性position为0out vec4 vertexColor; // 为像素着色器指定一个颜色输出void main(){    gl_Position = vec4(position, 1.0); // 把一个vec3作为vec4的构造器的参数    vertexColor = vec4(0.5f, 0.0f, 0.0f, 1.0f); // 把输出颜色设置为暗红色}

　　5、像素着色器：
　　

#version 330 corein vec4 vertexColor; // 和顶点着色器的vertexColor变量类型相同、名称相同out vec4 color; //像素着色器输出的变量名可以任意命名，类型必须是vec4void main(){    color = vertexColor;}

　　6、uniform
　　uniform 是另一种从CPU应用向GPU着色器发送数据的方式；
　　uniform和顶点属性的不同：
　　1）uniform是全局的：在所有着色器程序对象中都是独一无二的，可以在任何着色器程序的任何阶段使用，并且无论吧uniform值设置成什么，uniform都会一直保存着它们的数据，直到它们被重置或更新；
　　2）uniform是constant的：不能在着色器中修改，任何修改都会报错；
　　

456789#version 330 coreout vec4 color;uniform vec4 ourColor; // 在C++代码中设置void main(){    color = ourColor;}

绘制简单三角形
代码：

#define GLEW_STATIC#include <GL\glew.h>#include <GLFW\glfw3.h>#include<iostream>using namespace std;//函数原型void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode);//窗口大小const GLuint WIDTH = 800,HEIGHT = 600;const GLchar* vertexShaderSource = "#version 330 core\n"    "layout (location = 0) in vec3 position;\n"    "void main()\n"    "{\n"    "gl_Position = vec4(position.x,position.y,position.z,1.0);\n"    "}\0";const GLchar* fragmentShaderSource = "#version 330 core\n"    "out vec4 color;\n"    "void main()\n"    "{\n"    "color = vec4(1.0f,0.5f,0.2f,1.0f);\n"    "}\n\0";int main(){    //初始化 GLFW    glfwInit();    //设置GLFW需要的选项    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,3);    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);    glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_CORE_PROFILE);    glfwWindowHint(GLFW_RESIZABLE,GL_FALSE);    //创建一个窗口对象    GLFWwindow* window = glfwCreateWindow(WIDTH,HEIGHT,"test2",nullptr,nullptr);    glfwMakeContextCurrent(window);    //设置徐亚的回调函数    glfwSetKeyCallback(window,key_callback);    glewExperimental = GL_TRUE;    glewInit();    int width,height;    glfwGetFramebufferSize(window,&width,&height);    glViewport(0,0,width,height);    //定点着色器    GLuint vertextShader;    vertextShader = glCreateShader(GL_VERTEX_SHADER);    glShaderSource(vertextShader,1,&vertexShaderSource,NULL);    glCompileShader(vertextShader);    //用于判断一个着色器是否编译成功    GLint success;    GLchar infoLog[512];    glGetShaderiv(vertextShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(vertextShader,512,NULL,infoLog);        cout<<"vertextShader COMPILE FAILED"<<endl;    }    //像素着色器    GLuint fragmentShader;    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);    glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL);    glCompileShader(fragmentShader);    //用于判断一个着色器是否编译成功    glGetShaderiv(fragmentShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(fragmentShader,512,NULL,infoLog);        cout<<"fragmentShader COMPILE FAILED"<<endl;    }    //创建一个着色器程序对象：多个着色器最后链接的版本    GLuint shaderProgram;    shaderProgram = glCreateProgram();    glAttachShader(shaderProgram,vertextShader);    glAttachShader(shaderProgram,fragmentShader);    glLinkProgram(shaderProgram);    glGetProgramiv(shaderProgram,GL_LINK_STATUS,&success);    if(!success){        glGetProgramInfoLog(shaderProgram,512,NULL,infoLog);        }    glDeleteShader(vertextShader);    glDeleteShader(fragmentShader);    //创建定点数据    GLfloat vertices[] = {        -0.5f,-0.5f, 0.0f,        0.5f, -0.5f, 0.0f,        0.0f, 0.5f, 0.0f    };    //创建 VBO 顶点缓冲数据，并把数据赋值到内存中    GLuint VBO;    glGenBuffers(1,&VBO);    //VAO顶点数组对象    GLuint VAO;    glGenVertexArrays(1,&VAO);    //绑定VAO    glBindVertexArray(VAO);    //复制顶点数据到缓冲中提供给OpenGL使用    glBindBuffer(GL_ARRAY_BUFFER,VBO);    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);    //设置顶点属性指针    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,3*sizeof(GLfloat),(GLvoid *)0);    glEnableVertexAttribArray(0);    //解绑VBO    glBindBuffer(GL_ARRAY_BUFFER,0);    //解绑VAO    glBindVertexArray(0);    while(!glfwWindowShouldClose(window)){        glfwPollEvents();        //释放颜色缓存        glClearColor(0.2f,0.3f,0.3f,1.0f);        glClear(GL_COLOR_BUFFER_BIT);        //绘制物体        //当打算渲染一个物体使用使用着色器程序        glUseProgram(shaderProgram);        glBindVertexArray(VAO);        //绘制函数        glDrawArrays(GL_TRIANGLES,0,3);        glBindVertexArray(0);        glfwSwapBuffers(window);    }    glDeleteVertexArrays(1,&VAO);    glDeleteBuffers(1,&VBO);    glfwTerminate();    return 0;}void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode){                      if(key == GLFW_KEY_L && action == GLFW_PRESS){                          glfwSetWindowShouldClose(window,GL_TRUE);                      }}

绘制结果：

使用uniform绘制三角形示例代码：

#define GLEW_STATIC#include <GL\glew.h>#include <GLFW\glfw3.h>#include<iostream>#include<math.h>using namespace std;//函数原型void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode);//窗口大小const GLuint WIDTH = 800,HEIGHT = 600;//着色器const GLchar* vertexShaderSource = "#version 330 core\n"    "layout (location = 0) in vec3 position;\n"    "layout (location = 1) in vec3 color;\n"    "out vec3 ourColor;\n"    "void main()\n"    "{\n"    "gl_Position = vec4(position, 1.0);\n"    "ourColor = color;\n"    "}\0";const GLchar* fragmentShaderSource = "#version 330 core\n"    "out vec4 color;\n"    "uniform vec4 ourColor;\n"    "void main()\n"    "{\n"    "color = ourColor;\n"    "}\n\0";int main(){    //初始化 GLFW    glfwInit();    //设置GLFW需要的选项    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,3);    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);    glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_CORE_PROFILE);    glfwWindowHint(GLFW_RESIZABLE,GL_FALSE);    //创建一个窗口对象    GLFWwindow* window = glfwCreateWindow(WIDTH,HEIGHT,"test2",nullptr,nullptr);    glfwMakeContextCurrent(window);    //设置徐亚的回调函数    glfwSetKeyCallback(window,key_callback);    glewExperimental = GL_TRUE;    glewInit();    //定义 vierport 维度    glViewport(0,0,WIDTH,HEIGHT);    //定义点着色器    GLuint vertextShader;    vertextShader = glCreateShader(GL_VERTEX_SHADER);    glShaderSource(vertextShader,1,&vertexShaderSource,NULL);    glCompileShader(vertextShader);    //用于判断一个着色器是否编译成功    GLint success;    GLchar infoLog[512];    glGetShaderiv(vertextShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(vertextShader,512,NULL,infoLog);        cout<<"vertextShader COMPILE FAILED"<<endl;    }    //像素着色器    GLuint fragmentShader;    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);    glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL);    glCompileShader(fragmentShader);    //用于判断一个着色器是否编译成功    glGetShaderiv(fragmentShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(fragmentShader,512,NULL,infoLog);        cout<<"fragmentShader COMPILE FAILED"<<endl;    }    //创建一个着色器程序对象：多个着色器最后链接的版本    GLuint shaderProgram;    shaderProgram = glCreateProgram();    glAttachShader(shaderProgram,vertextShader);    glAttachShader(shaderProgram,fragmentShader);    glLinkProgram(shaderProgram);    glGetProgramiv(shaderProgram,GL_LINK_STATUS,&success);    if(!success){        glGetProgramInfoLog(shaderProgram,512,NULL,infoLog);        }    glDeleteShader(vertextShader);    glDeleteShader(fragmentShader);    //创建定点数据    GLfloat vertices[] = {        -0.5f,-0.5f, 0.0f,        0.5f, -0.5f, 0.0f,        0.0f, 0.5f, 0.0f    };    //创建 VBO 顶点缓冲数据，并把数据赋值到内存中    GLuint VBO;    glGenBuffers(1,&VBO);    //VAO顶点数组对象    GLuint VAO;    glGenVertexArrays(1,&VAO);    //绑定VAO    glBindVertexArray(VAO);    //复制顶点数据到缓冲中提供给OpenGL使用    glBindBuffer(GL_ARRAY_BUFFER,VBO);    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);    //设置顶点属性指针    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,3*sizeof(GLfloat),(GLvoid *)0);    glEnableVertexAttribArray(0);    //解绑VBO    glBindBuffer(GL_ARRAY_BUFFER,0);    //解绑VAO    glBindVertexArray(0);    while(!glfwWindowShouldClose(window)){        glfwPollEvents();        //释放颜色缓存        glClearColor(0.2f,0.3f,0.3f,1.0f);        glClear(GL_COLOR_BUFFER_BIT);        //绘制物体        //当打算渲染一个物体使用使用着色器程序        glUseProgram(shaderProgram);        //更新uniform颜色        GLfloat timeValue = glfwGetTime();        GLfloat greenValue = (sin(timeValue) /2 )+0.5;        GLint vertexColorLocation = glGetUniformLocation(shaderProgram,"ourColor");        glUniform4f(vertexColorLocation,0.0f,greenValue,0.0f,1.0f);        //绘制函数--->用于绘制三角形        glBindVertexArray(VAO);        glDrawArrays(GL_TRIANGLES,0,3);        glBindVertexArray(0);        glfwSwapBuffers(window);    }    glDeleteVertexArrays(1,&VAO);    glDeleteBuffers(1,&VBO);    glfwTerminate();    return 0;}void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode){                      if(key == GLFW_KEY_L && action == GLFW_PRESS){                          glfwSetWindowShouldClose(window,GL_TRUE);                      }}

效果：可以看到一个颜色随着时间发生变化的三角形；
绘制渐变色三角形：
代码：

#define GLEW_STATIC#include <GL\glew.h>#include <GLFW\glfw3.h>#include<iostream>#include<math.h>using namespace std;//函数原型void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode);//窗口大小const GLuint WIDTH = 800,HEIGHT = 600;//着色器const GLchar* vertexShaderSource ="#version 330 core\n"    "layout (location = 0) in vec3 position;\n"    "layout (location = 1) in vec3 color;\n"    "out vec3 ourColor;\n"    "void main()\n"    "{\n"    "gl_Position = vec4(position, 1.0);\n"    "ourColor = color;\n"    "}\0";const GLchar* fragmentShaderSource = "#version 330 core\n"    "in vec3 ourColor;\n"    "out vec4 color;\n"    "void main()\n"    "{\n"    "color = vec4(ourColor, 1.0f);\n"    "}\n\0";int main(){    //初始化 GLFW    glfwInit();    //设置GLFW需要的选项    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,3);    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);    glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_CORE_PROFILE);    glfwWindowHint(GLFW_RESIZABLE,GL_FALSE);    //创建一个窗口对象    GLFWwindow* window = glfwCreateWindow(WIDTH,HEIGHT,"test2",nullptr,nullptr);    glfwMakeContextCurrent(window);    //设置徐亚的回调函数    glfwSetKeyCallback(window,key_callback);    glewExperimental = GL_TRUE;    glewInit();    //定义 vierport 维度    glViewport(0,0,WIDTH,HEIGHT);    //定义点着色器    GLuint vertextShader;    vertextShader = glCreateShader(GL_VERTEX_SHADER);    glShaderSource(vertextShader,1,&vertexShaderSource,NULL);    glCompileShader(vertextShader);    //用于判断一个着色器是否编译成功    GLint success;    GLchar infoLog[512];    glGetShaderiv(vertextShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(vertextShader,512,NULL,infoLog);        cout<<"vertextShader COMPILE FAILED"<<endl;    }    //像素着色器    GLuint fragmentShader;    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);    glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL);    glCompileShader(fragmentShader);    //用于判断一个着色器是否编译成功    glGetShaderiv(fragmentShader,GL_COMPILE_STATUS,&success);    if(!success){        glGetShaderInfoLog(fragmentShader,512,NULL,infoLog);        cout<<"fragmentShader COMPILE FAILED"<<endl;    }    //创建一个着色器程序对象：多个着色器最后链接的版本    GLuint shaderProgram;    shaderProgram = glCreateProgram();    glAttachShader(shaderProgram,vertextShader);    glAttachShader(shaderProgram,fragmentShader);    glLinkProgram(shaderProgram);    glGetProgramiv(shaderProgram,GL_LINK_STATUS,&success);    if(!success){        glGetProgramInfoLog(shaderProgram,512,NULL,infoLog);        }    glDeleteShader(vertextShader);    glDeleteShader(fragmentShader);    //创建顶点数据     GLfloat vertices[] = {        // Positions         // Colors         0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,  // Bottom Right        -0.5f, -0.5f, 0.0f,  0.0f, 1.0f, 0.0f,  // Bottom Left         0.0f,  0.5f, 0.0f,  0.0f, 0.0f, 1.0f   // Top     };    //创建 VBO 顶点缓冲数据，并把数据赋值到内存中    GLuint VBO;    glGenBuffers(1,&VBO);    //VAO顶点数组对象    GLuint VAO;    glGenVertexArrays(1,&VAO);    //绑定VAO    glBindVertexArray(VAO);    //复制顶点数据到缓冲中提供给OpenGL使用    glBindBuffer(GL_ARRAY_BUFFER,VBO);    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);    //设置顶点属性指针    //位置属性    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);    glEnableVertexAttribArray(0);    //颜色属性    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));    glEnableVertexAttribArray(1);    //解绑VAO    glBindVertexArray(0);    while(!glfwWindowShouldClose(window)){        glfwPollEvents();        //释放颜色缓存        glClearColor(0.2f,0.3f,0.3f,1.0f);        glClear(GL_COLOR_BUFFER_BIT);        //绘制物体        //当打算渲染一个物体使用使用着色器程序        glUseProgram(shaderProgram);        //绘制函数--->用于绘制三角形        glBindVertexArray(VAO);        glDrawArrays(GL_TRIANGLES,0,3);        glBindVertexArray(0);        glfwSwapBuffers(window);    }    glDeleteVertexArrays(1,&VAO);    glDeleteBuffers(1,&VBO);    glfwTerminate();    return 0;}void key_callback(GLFWwindow* window, int key,int scancode,                  int action,int mode){                      if(key == GLFW_KEY_L && action == GLFW_PRESS){                          glfwSetWindowShouldClose(window,GL_TRUE);                      }}

效果：