计算机图形学OpenGLC++实现： 橡皮筋技术实现折线和矩形的鼠标实现（附源码）

废话不多说，直接开始

下列是会使用到的函数简单介绍：

• 初始化背景 void Initial(void)
• 改变窗口大小 void ChangeSize(int w,int h)
• 菜单响应函数 chooseWay(int value)
• 清除当前已经画的图形 void clear(void)
• 画图函数 void Display(void)
• 鼠标点击事件响应函数
  void MousePlot(GLint button,GLint action,GLint xMouse,GLint yMouse)
• 鼠标跟踪函数 void PassiveMouseMove(GLint xMouse,GLint yMouse)

首先，让我们看看主函数

int main(int argc,char* argv[])
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
    //创建窗口，并设置大小为长400宽300
    glutInitWindowSize(400,300);
    glutInitWindowPosition(100,100);
    glutCreateWindow("橡皮筋技术");
	
	//向鼠标右键注册菜单-选择画折线还是矩形
    glutCreateMenu(chooseWay);				//菜单函数
    glutAddMenuEntry("BrokenLine", 1);		//折线选项
    glutAddMenuEntry("Actangle", 2);		//矩形选项
    glutAddMenuEntry("Clear", 0);			//清空选项
    glutAttachMenu(GLUT_RIGHT_BUTTON);		//将该菜单绑定在右键
	Initial();								//初始化函数
	glutReshapeFunc(ChangeSize);			//调用改变窗口函数
    glutDisplayFunc(Display);				//调用画图函数
    glutMouseFunc(MousePlot);				//调用鼠标点击事件函数
    glutPassiveMotionFunc(PassiveMouseMove);//调用鼠标追踪事件函数
    glutMainLoop();

    return 0;
}

初始化函数，glClearColor函数向缓存写入颜色值

//初始化函数
void Initial(void)
{
    glClearColor(0.5f,0.5f,0.75f,1.0f);		//设置背景颜色
}

//改变窗口大小函数

void ChangeSize(int w,int h)
{
    winWidth=w,winHeight=h;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();               //调用单位矩阵，去除以前投影参数设置
    gluOrtho2D(0.0,winWidth,0.0,winHeight);
}

//清除当前已经画的图形

void clear(void)
{
    int flag = iPointNum;
    iPointNum = 0;
    for (int i = 0; i < flag; ++i)
    {
        x[i] = 0;
        y[i] = 0;
    }
    glutPostRedisplay();				//清除后重画
}

菜单选择函数

void chooseWay(int value)
{
    switch (value)
    {
    case 0:clear(); break;
    case 1:choose=1; break;		//画折线
    case 2:choose=2; break;		//画矩形
    default:
        choose = 1;break;		//默认画折线
    }
}

鼠标点击响应函数

void MousePlot(GLint button,GLint action,GLint xMouse,GLint yMouse)
{
    if (choose == 1)				//画折线
    {
        if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN)	
        //左键按下判定
        {
            if (iPointNum == 0)
            //已经点击的点数
            {
                x[iPointNum] = xMouse;
                y[iPointNum] = winHeight - yMouse;		//坐标转换
                iPointNum += 1;
            }
            else
            {
                x[iPointNum] = xMouse;
                y[iPointNum] = winHeight - yMouse;
                iPointNum += 1;
                glutPostRedisplay();
            }
        }
    }
    if (choose == 2)			//画矩形
    {
        if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN)
        {
            if (iPointNum== 0||iPointNum==2)
            {
                x[0] = xMouse;
                y[0] = winHeight - yMouse;
                iPointNum = 1;
            }
            else
            {
                x[1] = xMouse;
                y[1] = winHeight - yMouse;
                iPointNum = 2;
                glutPostRedisplay();
            }
        }
    }
}

鼠标跟踪函数

void PassiveMouseMove(GLint xMouse,GLint yMouse)
{
    if (choose == 1 && iPointNum >=1)
    {
        x[iPointNum] = xMouse;
        y[iPointNum] = winHeight - yMouse;
        glutPostRedisplay();
    }
    if(choose==2&&iPointNum==1)
    {
        x[iPointNum]=xMouse;
        y[iPointNum]=winHeight-yMouse;
        glutPostRedisplay();
    }
}

画图函数

void Display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    if(choose==1)
    {
        if (iPointNum >= 1)
        {
            glColor3f(1.0f, 0.0f, 0.0f);
            int flag = iPointNum;
            glBegin(GL_LINE_STRIP);
            while (flag)
            {
                glVertex2f(x[flag], y[flag]);
                glVertex2f(x[flag - 1], y[flag - 1]);
                flag--;
            }
            glEnd();
        }
    }
    //画矩形
    if (choose == 2)
    {
        if (iPointNum >=1)
        {
            glColor3f(1.0f, 0.0f, 0.0f);
            glBegin(GL_QUADS);
            glVertex2f(x[0], y[0]);
            glVertex2f(x[0], y[1]);
            glVertex2f(x[1], y[1]);
            glVertex2f(x[1], y[0]);
            glEnd();
        }
    }
    glutSwapBuffers();
}

把上述拼接起来就可以完整运行，希望对你有所帮助！