Back to openGL!

#include <iostream>
#include <windows.h>  
#include <gl/glut.h>  
#include <math.h>
#include <gl/gl.h>
/* back to openGL  2016/9/19  magic  */
//thanks to:    http://blog.csdn.net/bill_ming/article/details/7662809
using namespace std; 

#define pi 3.1415926
#define  GLUT_WHEEL_UP 3           //定义滚轮操作  
#define  GLUT_WHEEL_DOWN 4  


int mx,my;
int ry=0;int rx=0;    //turnning angle around X/Y axis following right-hand rule
int i=0;
GLdouble a=0.2;    //size of teapot
bool mouseisdown=false;
bool loopr=false;

void timer(int p)
{
     ry-=5;
        glutPostRedisplay();    //marks the current window as needing to be redisplayed.
     if (loopr)
         glutTimerFunc(10,timer,0);
}

void motion(int x, int y)
{
 if(mouseisdown==true)
    {
//       cout<<mx<<" "<<my<<" "<<i<<endl;
        ry+=x-mx;
        rx+=y-my;
        mx=x;my=y;
        glutPostRedisplay();
    }
}

void mouse(int button, int state, int x, int y)
{
    if(button == GLUT_LEFT_BUTTON)
     {
//         cout<<"left click!"<<endl;
        mx=x;my=y;   //Initialize mx my 9/20
         
        if(state == GLUT_DOWN)
        {    mouseisdown=true; loopr=false;}
        else
            mouseisdown=false;
     }
    if (button== GLUT_RIGHT_BUTTON)
        if(state == GLUT_DOWN)
        {loopr=true; glutTimerFunc(200,timer,0);}  
    if (button== GLUT_MIDDLE_BUTTON)
    {
//        cout<<"wheel"<<endl;
        if(state == GLUT_DOWN){
            a+=0.1;
            glutPostRedisplay();
        }
    }
}

void special(int key, int x, int y)
{
    switch(key)
    {
    case GLUT_KEY_LEFT:
        ry-=5;
        glutPostRedisplay();
        break;

    case GLUT_KEY_RIGHT:
       ry+=5;
        glutPostRedisplay();
        break;

    case GLUT_KEY_UP:
        rx+=5;
        glutPostRedisplay();
        break;

    case GLUT_KEY_DOWN:
        rx-=5;
        glutPostRedisplay();
        break;
        
    }
}

void special_1(unsigned char key, int x, int y){
    
    switch(key){
        case 'a':
        a+=0.1;
        glutPostRedisplay();
        break;
    case 'z':
        a-=0.1;
        glutPostRedisplay();
        break;
    }
}


void display0(void)
{      
        float red[3]={1,0,0};
        float blue[3]={0,1,0};
        float green[3]={0,0,1};
        float yellow[3]={1,1,0};   
        
        glClearColor(1,0,1,1);
        glClear(GL_COLOR_BUFFER_BIT);
        glLoadIdentity();
        glRotatef(ry,0,1,0);      
        glRotatef(rx,1,0,0);
        glColor3fv(green);
        
        glutWireTeapot(a);

        glFlush();
}


int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE| GLUT_RGBA);
    glutInitWindowSize (600, 600);
    glutInitWindowPosition(100,100);     
    glutCreateWindow ("A TEAPOT");     //window initializing

    glutDisplayFunc (display0);    
    glutMouseFunc(mouse);    //message processing function
    glutMotionFunc(motion);
    glutSpecialFunc(special);
    glutKeyboardFunc(special_1);
    glutMainLoop();      

    return 0;
}

 back to openGL

这是一个初级的openGL编程例子，实现了程序对键鼠操作消息的处理：
1.鼠标拖拽使模型跟随光标旋转；
2.按'A'或双击鼠标中键放大，按'Z'缩小；
3.单击鼠标右键使模型旋转；
4.方向键（上下左右）使模型旋转