OpenGL学习笔记5——嵌入Qt框架

　　学习OpenGL也有段时间了，前几篇将GL最基本的画图过程解析了一下，后面进阶的就随项目需要再学。因为之前一直是用glut这个实用工具包来开发很方便，但是会附带一个控制台的窗口，实在觉得有些low，因此就打算将GL嵌入到应用程序中去。

　　下面就把前几章学习的知识结合起来，在QT下实现GL的动画。之所以选QT而非MFC原因有2点，一则是QT是开源的，现在开源的东西都很热闹，所以我也凑凑热闹，之前用MFC做过别的上位机程序，我是个喜欢图新鲜的人；二则QT的移植性好，一次编译到处运行吧。

　　总结几处注意点：

　　1.glut的函数是一个也不能使用了，需要自己用QT的Widget类来创建应用窗口，同时再用QGLWidget类创建自己的GL类，将二者绑定在一起；

　　2.需要重载QGLWidget的三个重要函数initializeGL、resizeGL和paintGL；

　　3.glClear函数不属于initializeGL，即即使你写入它，在初始化的时候也不会被执行；

　　4.需要显示裁剪视口以及设定透视方法，这些在之前使用glut中函数的时候会被默认设置和创建窗口匹配。什么意思呢？就是如果不显示设定的话，你会被坐标定位搞得糊里糊涂。这个也是我第一次移植时候遇到的困扰，其实程序是正常运行的，但是要嘛图像歪斜要嘛看不到图像。如果以上一些设置成功，就能随心所欲绘制；

　　5.glut中的消息响应在QT中都有各自的类；

　　6.QT的类不比MFC类来的“苗条”,用到哪个查找哪个就ok。

　　最后上代码。

功能说明文件：

--use keyboard to control the cube
-w-    accelerate the rolling speed;
-s-    slow down the rolling speed;
-a-    change the rolling direction;
-d-    opposite with -a-;
-r-    reset the initial state;
-c-    change color

主函数文件：

#include<QApplication>
#include"myglwidget.h"
int main(int argc,char *argv[])
{
    QApplication MyApp(argc,argv);
    MyGLWidget MyGL;
    MyGL.show();
    return MyApp.exec();
}

自定义GL类头文件：

#ifndef MYGLWIDGET_H
#define MYGLWIDGET_H

#include <QGLWidget>
#include<QTime>
#include<QTimerEvent>
#include<QKeyEvent>
class MyGLWidget : public QGLWidget
{
    Q_OBJECT
public:
    explicit MyGLWidget(QWidget *parent = 0);

signals:
private:
//    GLfloat VertexData[24];
//    GLubyte VertexIndex[6][4];
    float m_rotate;
    float m_speed;
    bool m_angle;
    GLubyte m_color_mode;
    int m_T20msID;
    void initializeGL();
    void resizeGL(int w, int h);
    void paintGL();
    void timerEvent(QTimerEvent *);
    void keyPressEvent(QKeyEvent *);
    void Cross(GLfloat,GLubyte);
    void ChangeColor(GLubyte mode,GLfloat value);
    float GetRand(int,int);
    void Draw(void);
    void Cube(void);
public slots:
};

#endif // MYGLWIDGET_H

自定义GL类实现：

#include "myglwidget.h"
static GLfloat VertexData[] = {
    -0.5f, -0.5f, -0.5f,
     0.5f, -0.5f, -0.5f,
    -0.5f,  0.5f, -0.5f,
     0.5f,  0.5f, -0.5f,
    -0.5f, -0.5f,  0.5f,
     0.5f, -0.5f,  0.5f,
    -0.5f,  0.5f,  0.5f,
     0.5f,  0.5f,  0.5f,
};
static GLubyte VertexIndex[][4] = {
    0, 2, 3, 1,
    0, 4, 6, 2,
    0, 1, 5, 4,
    4, 5, 7, 6,
    1, 3, 7, 5,
    2, 6, 7, 3,
};
MyGLWidget::MyGLWidget(QWidget *parent) :
    QGLWidget(parent)
{
    m_speed = 2.0;
    m_angle = 0;
    m_color_mode = 0;
    m_rotate = 0;
    m_T20msID = 0;
}
void MyGLWidget::initializeGL()
{
    glClearColor(0,0,0,0);
    glClearDepth(1);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    m_T20msID = startTimer(20);
    qsrand(QTime::currentTime().msec());
}
void MyGLWidget::resizeGL(int w, int h)
{
   glViewport(0,0,w,h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if(w <= h)
       glOrtho(-1, 1, -(GLfloat)h/(GLfloat)w, (GLfloat)h/(GLfloat)w, -1, 1);
   else
       glOrtho(-(GLfloat)w/(GLfloat)h, (GLfloat)w/(GLfloat)h, -1, 1, -1, 1);
}
void MyGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    Draw();
}
void MyGLWidget::Cube(void)
{
    //enable vertex_array
    glEnableClientState(GL_VERTEX_ARRAY);
    //load vertex_array data
    glVertexPointer(3,GL_FLOAT,3*sizeof(GLfloat),VertexData);
    //drawing operation
    glDrawElements(GL_QUADS,sizeof(VertexData),GL_UNSIGNED_BYTE,VertexIndex);
}
void MyGLWidget::timerEvent(QTimerEvent *event)
{
    if(m_T20msID == event->timerId())
    {
        updateGL();
    }
}
float MyGLWidget::GetRand(int start, int end)
{
    return start + (end - start)*qrand()/(RAND_MAX + 1.0);
}
void MyGLWidget::Cross(GLfloat coordinater,GLubyte face)
{
        GLfloat rand;
        switch(face)
        {
                //front
                case 0:    rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(-0.5f,rand,coordinater);
                                                glVertex3f(0.5f,rand,coordinater);
                                        glEnd();
                                        rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(rand,0.5f,coordinater);
                                                glVertex3f(rand,-0.5f,coordinater);
                                        glEnd();
                                        break;
                //left
                case 1:    rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(coordinater,-0.5f,rand);
                                                glVertex3f(coordinater,0.5f,rand);
                                        glEnd();
                                        rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(coordinater,rand,0.5f);
                                                glVertex3f(coordinater,rand,-0.5f);
                                        glEnd();
                                        break;
                case 2:    rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(-0.5f,coordinater,rand);
                                                glVertex3f(0.5f,coordinater,rand);
                                        glEnd();
                                        rand = (GetRand(0,10)-5)/10;
                                        glBegin(GL_LINES);
                                                glVertex3f(rand,coordinater,0.5f);
                                                glVertex3f(rand,coordinater,-0.5f);
                                        glEnd();
                                        break;
                default:break;
        }
}
void MyGLWidget::Draw()
{
    m_rotate += (m_angle)?m_speed:-m_speed;
    glRotatef(m_rotate,1,0,0);
    glRotatef(m_rotate,0,1,0);
    glRotatef(m_rotate,0,0,1);
    glColor3f(0,0,0);
    //front-red
    Cube();
    int i;
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(0,33)/100,0);
            ChangeColor(m_color_mode,GetRand(0,20)/100);
            glLineWidth(GetRand(1,10));
            Cross(0.5f,0);
    }
    //back-green
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(0,20)/100,0);
            ChangeColor(m_color_mode,GetRand(0,20)/100);
            glLineWidth(GetRand(1,10));
            Cross(-0.5f,0);
    }
    //left-blue
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(46,66)/100,0);
            ChangeColor(m_color_mode,GetRand(46,66)/100);
            glLineWidth(GetRand(1,10));
            Cross(-0.5f,1);
    }
    //right
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(33,66)/100,0);
            ChangeColor(m_color_mode,GetRand(46,66)/100);
            glLineWidth(GetRand(1,10));
            Cross(0.5f,1);
    }
    //up
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(80,100)/100,0);
            ChangeColor(m_color_mode,GetRand(80,100)/100);
            glLineWidth(GetRand(1,10));
            Cross(0.5f,2);
    }
    //bottom
    for(i=0;i<50;i++)
    {
            //glColor3f(0,GetRand(66,100)/100,0);
            ChangeColor(m_color_mode,GetRand(80,100)/100);
            glLineWidth(GetRand(1,10));
            Cross(-0.5f,2);
    }

}
void MyGLWidget::ChangeColor(GLubyte mode,GLfloat value)
{
        switch(mode)
        {
                case 0:glColor3f(0,value,0);
                                        break;
                case 1:glColor3f(value,0,0);
                                        break;
                case 2:glColor3f(0,0,value);
                                        break;
                case 3:glColor3f(value,value,0);
                                        break;
                case 4:glColor3f(value,0,value);
                                        break;
                case 5:glColor3f(0,value,value);
                                        break;
                case 6:glColor3f(value,value,value);
                default:break;
        }
}
void MyGLWidget::keyPressEvent(QKeyEvent *event)
{
    switch(event->key())
    {
    case Qt::Key_A:m_angle = 1;
        break;
    case Qt::Key_W:m_speed += 0.5;
        break;
    case Qt::Key_D:m_angle = 0;
        break;
    case Qt::Key_S:if((m_speed-0.25)<0)
                        m_speed = 0;
                    else
                        m_speed -= 0.25;
        break;
    case Qt::Key_R:m_speed = 2;
                   m_angle = 1;
                   break;
    case Qt::Key_C:if(m_color_mode == 6)
                        m_color_mode = 0;
                    else
                        m_color_mode++;
                    break;
    case Qt::Key_F:showFullScreen();
                    break;
    case Qt::Key_Escape:close();
    default:break;
    }
}