目录

1. OpenGL初识 - 点的绘制

2. OpenGL初识 - 简单图形绘制

3. 直线光栅化 - 使用OpenGL绘制直线

4. 直线光栅化 - DDA画线算法

5. 直线光栅化 - 中点画线算法

1. OpenGL初识 - 点的绘制

在这一部分，我们将学习如何使用OpenGL绘制点。以下是具体的代码示例：

#include 
#include 

void myDisplay(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glPointSize(3.0);
    glBegin(GL_POINTS);
        glColor3f(1.0f, 0.0f, 0.0f); glVertex2f(-0.4f, -0.4f);
        glColor3f(0.0f, 1.0f, 0.0f); glVertex2f(0.0f, 0.0f);
        glColor3f(0.0f, 0.0f, 1.0f); glVertex2f(0.4f, 0.4f);
    glEnd();
    glFlush();
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Point!");
    glutDisplayFunc(myDisplay);
    glutMainLoop();
    return 0;
}

2. OpenGL初识 - 简单图形绘制

接下来，我们扩展到绘制简单的几何图形，如矩形和三角形。以下是代码示例：

#include 
#include 

void myDisplay(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0f, 1.0f, 1.0f);
    glRectf(-0.5f, -0.5f, 0.5f, 0.5f);
    glBegin(GL_TRIANGLES);
        glColor3f(1.0f, 0.0f, 0.0f); glVertex2f(0.0f, 1.0f);
        glColor3f(0.0f, 1.0f, 0.0f); glVertex2f(0.8f, -0.5f);
        glColor3f(0.0f, 0.0f, 1.0f); glVertex2f(-0.8f, -0.5f);
    glEnd();
    glPointSize(3);
    glBegin(GL_POINTS);
        glColor3f(1.0f, 0.0f, 0.0f); glVertex2f(-0.4f, -0.4f);
        glColor3f(0.0f, 1.0f, 0.0f); glVertex2f(0.0f, 0.0f);
        glColor3f(0.0f, 0.0f, 1.0f); glVertex2f(0.4f, 0.4f);
    glEnd();
    glFlush();
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Point!");
    glutDisplayFunc(myDisplay);
    glutMainLoop();
    return 0;
}

3. 直线光栅化 - 使用OpenGL绘制直线

在这里，我们将学习如何使用OpenGL绘制直线。以下是代码示例：

#include 
#include 

void myDisplay(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0f, 0.0f, 0.0f);
    glBegin(GL_LINES);
        glVertex2f(0.0f, 0.0f);
        glVertex2f(100.0f, 240.0f);
    glEnd();
    glFlush();
}

void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}

void myReshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Point!");
    Init();
    glutDisplayFunc(myDisplay);
    glutReshapeFunc(myReshape);
    glutMainLoop();
    return 0;
}

4. 直线光栅化 - DDA画线算法

DDA（数字微分分析器）算法是一种常用的直线光栅化算法。以下是实现该算法的代码示例：

#include 
#include 

void LineDDA(int x0, int y0, int x1, int y1)
{
    int dx = x1 - x0, dy = y1 - y0;
    float k = dy / (float)dx;
    int y = y0;
    glColor3f(1.0f, 1.0f, 0.0f);
    glPointSize(1);
    for (int x = x0; x <= x1; x++) {
        glBegin(GL_POINTS);
            glVertex2i(x, (int)(y + 0.5));
        glEnd();
        y += k;
    }
    glFlush();
}

void myDisplay(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    LineDDA(0, 0, 200, 300);
    glFlush();
}

void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}

void myReshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Point!");
    Init();
    glutDisplayFunc(myDisplay);
    glutReshapeFunc(myReshape);
    glutMainLoop();
    return 0;
}

5. 直线光栅化 - 中点画线算法

中点画线算法是另一种高效的直线光栅化方法。以下是其实现代码：

#include 
#include 

void MidPLine(int x0, int y0, int x1, int y1)
{
    int dx = x1 - x0, dy = y1 - y0;
    int d = dx - 2 * dy;
    int dt = 2 * dx - 2 * dy;
    int db = -2 * dy;
    int x = x0, y = y0;
    glColor3f(0.0f, 1.0f, 0.0f);
    glPointSize(1);
    glBegin(GL_POINTS);
        glVertex2i(x, y);
    glEnd();
    while (x         if (d <0) {
            x++;
            y++;
            d += dt;
        } else {
            x++;
            d += db;
        }
        glBegin(GL_POINTS);
            glVertex2i(x, y);
        glEnd();
    }
    glFlush();
}

void myDisplay(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    MidPLine(10, 50, 300, 260);
    glFlush();
}

void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}

void myReshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("Hello Point!");
    Init();
    glutDisplayFunc(myDisplay);
    glutReshapeFunc(myReshape);
    glutMainLoop();
    return 0;
}