GLFW是现在较流行、使用广泛的OpenGL的界面库，而glut库已经比较老了。GLEW是和管理OpenGL函数指针有关的库，因为OpenGL只是一个标准/规范，具体的实现是由驱动开发商针对特定显卡实现的。由于OpenGL驱动版本众多，它大多数函数的位置都无法在编译时确定下来，需要在运行时查询，而GLEW可以解决这些问题。下面就来看下OpenGL是如何基于glfw库实现画点、画线、画三角的。

1、glVertex函数

2、坐标系

代码如下：

#include <GLFW/glfw3.h>
void drawPoint()
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    /* Draw a point */
    glClearColor (0.0, 0.0, 0.0, 0.0); 
    glClear(GL_COLOR_BUFFER_BIT);
    glPointSize(2.0f);
    glBegin(GL_POINTS);
    glColor3f(1.0, 0.0, 0.0);    // Red
    glVertex2f(0.0f,0.0f);
    glVertex2f(0.5f,0.8f);
    glEnd();
｝
void drawLint()
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    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLineWidth(2);//设置线段宽度
    glBegin(GL_LINES);
    glColor3f(1.0,0.0,0.0);
    glVertex2f(0.8,1); //定点坐标范围
    glVertex2f(0,-1);
    glEnd();
｝
void drawTriangle()
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    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glBegin(GL_TRIANGLES);
    glColor3f(1.0, 0.0, 0.0);    // Red
    glVertex3f(0.0, 1.0, 0.0);
    glColor3f(0.0, 1.0, 0.0);    // Green
    glVertex3f(-1.0, -1.0, 0.0);
    glColor3f(0.0, 0.0, 1.0);    // Blue
    glVertex3f(1.0, -1.0, 0.0);
    glEnd();
｝
int main(void)
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    GLFWwindow* window;
    /* Initialize the library */
    if (!glfwInit())
        return -1;
    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(480, 320, "Hello World", NULL, NULL);
    if (!window)
    ｛
        glfwTerminate();
        return -1;
    ｝
    /* Make the window's context current */
    glfwMakeContextCurrent(window);
    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    ｛
        /*your draw*/
        // drawPoint();
        // drawLint();
        drawTriangle();
        /* Swap front and back buffers */
        glfwSwapBuffers(window);
        /* Poll for and process events */
        glfwPollEvents();
    ｝
    glfwTerminate();
    return 0;
｝

运行效果