计算机图形学-橡皮筋

#include <GL/glut.h>
#include <GL/glu.h>

int iPointNum = 0;                          //已经确定的点的数量
int x1 = 0, x2 = 0, y1 = 0, y2 = 0;         //确定的点坐标
int winWidth = 400, winHeight = 300;

void Initial(void)
{
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);  //设置背景色为白色
}

void ChangeSize(int w, int h)
{
    winWidth = w;
    winHeight = h;
    glViewport(0, 0, w, h);        //指定窗口显示区域
    glMatrixMode(GL_PROJECTION);   //指定设置投影参数
    glLoadIdentity();              //调用单位矩阵，去掉以前的投影参数设置
    gluOrtho2D(0.0, winWidth, 0.0, winHeight); //设置投影参数
}

void Display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);  //使用背景色填充窗口
    glColor3f(1.0f, 0.0f, 0.0f);   //指定绘图颜色为红色
    if (iPointNum >= 1)                                   //绘制直线段 
    {
        glBegin(GL_LINES);
        glVertex2i(x1, y1);
        glVertex2i(x2, y2);
        glEnd();
    }
    glutSwapBuffers();   //交换缓存区
}

void MousePlot(GLint button, GLint action, GLint xMouse, GLint yMouse)
{
    if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN) { //按下左键
        if (iPointNum == 0 || iPointNum == 2) {
            iPointNum = 1;
            x1 = xMouse;
            y1 = winHeight - yMouse;
        }
        else {
            iPointNum = 2;
            x2 = xMouse;
            y2 = winHeight - yMouse;
            glutPostRedisplay();  //强制刷新窗口  指定窗口重新绘制
        }
    }
    if (button == GLUT_RIGHT_BUTTON && action == GLUT_DOWN) { //按下右键
        iPointNum = 0;
        glutPostRedisplay();
    }
}

void PassiveMouseMove(GLint xMouse, GLint yMouse)
{
    if (iPointNum == 1) {
        x2 = xMouse;
        y2 = winHeight - yMouse;
        glutPostRedisplay();
    }
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(400, 300);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("橡皮筋技术");
    glutDisplayFunc(Display);
    glutReshapeFunc(ChangeSize);   //指定窗口再整形回调函数
    glutMouseFunc(MousePlot);      //指定鼠标响应函数
    glutPassiveMotionFunc(PassiveMouseMove); //指定鼠标移动响应函数
    Initial();
    glutMainLoop();
    return 0;
}