openGL学习笔记六： glew库及使用

window默认支持到OpenGL1.3，后续也没有更新，opengl并不是以API更新或者新的开发包方式更新功能，它使用了扩展方式获取高版本新的功能。

如执行扩展功能函数glArrayElementEXT：代码如下

        char* ext = (char*)glGetString(GL_EXTENSIONS); //获取该电脑显卡支持的扩展函数结合PFNGLARRAYELEMENTEXTPROC glArrayElementEXT = (PFNGLARRAYELEMENTEXTPROC)wglGetProcAddress("glArrayElementEXT"); //获取扩展函数glArrayElementEXT 指针glArrayElementEXT(0); //通过函数glArrayElementEXT 指针 调用扩展函数glArrayElementEXT

上面这样获取扩展功能的方式很麻烦，所以就诞生了glew，是一个跨平台的C++扩展库，方便开发者使用opengl扩展功能。

安装及使用

环境：win7 VS2013

1. 下载glew：

地址：https://github.com/Perlmint/glew-cmake

2. 打开生成glew VS工程：

在build目录下选择对应版本的VS工程打开,我使用的是VS2013打开 VC12目录下glew.sln

glew_shared ：是编译动态链接库
glew_static ：是编译静态库

根据自己情况选择一种方式，我这里选择glew_static 。
编译之后得到glew32sd.lib

3. opengl项目配置：

a. 项目属性 ----> C/C++ —> 附加包含目录 —> your_path\glew-master\include
b. 项目属性 ----> 链接器 —> 常规 —> 附加库目录 —> your_path\lib
c. 项目属性 ----> 链接器 —> 输入 —> 附加依赖项 —> glew32sd.lib

4. 代码：

注意: glew.h要放在glfw3.h glut.h 之前，并定义宏 GLEW_STATIC


#include <iostream>
// GLEW
#define GLEW_STATIC    #include <GL/glew.h>
#include <Windows.h>
// GLFW
#include <GLFW/glfw3.h>
#pragma comment(lib,"winmm.lib") // 告诉连接器与这个库连接，因为我们要播放多媒体声音
#pragma comment(linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"" )
//#define DEBUG
// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);// Window dimensions
const GLuint WIDTH = 800, HEIGHT = 600;// The MAIN function, from here we start the application and run the game loop
//#ifdef DEBUG
//int main()
//#else
//int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
//#endif
int main() {std::cout << "Starting GLFW context, OpenGL 3.3" << std::endl;// Init GLFW    glfwInit();// Set all the required options for GLFW    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);// Create a GLFWwindow object that we can use for GLFW's functions    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "win view", nullptr, nullptr);if(window == nullptr) {std::cout << "Failed to create GLFW window" << std::endl;glfwTerminate();return -1;}glfwMakeContextCurrent(window);// Set the required callback functions    glfwSetKeyCallback(window, key_callback);// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions    glewExperimental = GL_TRUE;// Initialize GLEW to setup the OpenGL Function pointers    if(glewInit() != GLEW_OK) {std::cout << "Failed to initialize GLEW" << std::endl;return -1;}// Define the viewport dimensions    glViewport(0, 0, WIDTH, HEIGHT);// Game loop    while(!glfwWindowShouldClose(window)) {// Check if any events have been activiated (key pressed, mouse moved etc.) and call corresponding response functions    glfwPollEvents();// Render    // Clear the colorbuffer    glClearColor(1.0f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);/* Draw a triangle */glBegin(GL_TRIANGLES);glColor3f(1.0, 0.0, 0.0);    // RedglVertex3f(0.0, 1.0, 0.0);glColor3f(0.0, 1.0, 0.0);    // GreenglVertex3f(-1.0, -1.0, 0.0);glColor3f(0.0, 0.0, 1.0);    // BlueglVertex3f(1.0, -1.0, 0.0);glEnd();/* Swap front and back buffers */glfwSwapBuffers(window);//Sleep(20);}// Terminate GLFW, clearing any resources allocated by GLFW.    glfwTerminate();return 0;
}// Is called whenever a key is pressed/released via GLFW
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode) {std::cout << key << std::endl;if(key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)glfwSetWindowShouldClose(window, GL_TRUE);
}

5. 运行结果：