46.Qt 使用OpenGL绘制立方体

main.cpp

#include <QApplication>

#include <iostream>

#include "vowelcube.h"

int main(int argc, char *argv[])

{

    QApplication app(argc, argv);

    if (!QGLFormat::hasOpenGL()) {

        std::cerr << "This system has no OpenGL support" << std::endl;

        return ;

    }

    VowelCube cube;

    cube.setWindowTitle(QObject::tr("Vowel Cube"));

    cube.setMinimumSize(, );

    cube.resize(, );

    cube.show();

    return app.exec();

}

vowelcube.h

#ifndef VOWELCUBE_H

#define VOWELCUBE_H

#include <QGLWidget>

#include <QRadialGradient>

//使用OpenGL绘制立方体，使用QPainter绘制背景

//的渐变，接着使用renderText（）绘制立方体角上的8个

//元音字母，最后使用QPainter和QTextDocument绘制图例。

//用户可以单击并拖动鼠标来旋转立方体，并且可以使用鼠标滚轮进行放大或缩小

class VowelCube : public QGLWidget

{

    Q_OBJECT

public:

    VowelCube(QWidget *parent = );

    ~VowelCube();

protected:

    void paintEvent(QPaintEvent *event);

    void mousePressEvent(QMouseEvent *event);

    void mouseMoveEvent(QMouseEvent *event);

    void wheelEvent(QWheelEvent *event);

private:

    void createGradient();

    void createGLObject();

    void drawBackground(QPainter *painter);

    void drawCube();

    void drawLegend(QPainter *painter);

    GLuint glObject;

    QRadialGradient gradient;

    GLfloat rotationX;

    GLfloat rotationY;

    GLfloat rotationZ;

    GLfloat scaling;

    QPoint lastPos;

};

#endif

vowelcube.cpp

 #include <QtGui>

 #include <QtOpenGL>

 #include <cmath>

 #ifndef GL_MULTISAMPLE

 #define GL_MULTISAMPLE 0x809D

 #endif

 #include "vowelcube.h"

 VowelCube::VowelCube(QWidget *parent)

     : QGLWidget(parent)

 {

     //调用setFormat（）使OpenGL的显示描述表支持饭走样。

     setFormat(QGLFormat(QGL::SampleBuffers));

     //初始化私有变量

     rotationX = -38.0;

     rotationY = -58.0;

     rotationZ = 0.0;

     scaling = 1.0;

     //设置填充背景的QRadialGradient

     createGradient();

     //创建OpenGL立方体对象

     createGLObject();

     setAutoBufferSwap( false );

     setAutoFillBackground( false );

 }

 VowelCube::~VowelCube()

 {

     makeCurrent();

     //删除构造函数创建的OpenGL立方体对象

     glDeleteLists(glObject, );

 }

 //绘制,在paintEvent()中创建一个QPainter,在进行纯OpenGL操作时

 //保存和恢复其状态。

 //QPainter的构造函数(或者QPainter::begin())自动调用glClear

 //除非预先调用窗口部件的setAutoFillBackground(false)

 //QPainter的析构函数（或者QPainter::end()）自动调用QGLWidget::swapBuffers()

 //切换可见缓存和离屏缓存，除非预先调用setAutoBufferSwap(false).

 //当QPainter被激活，我们可以交叉使用纯OpenGL命令，只要在执行纯OpenGL命令之前保存OpenGL状态，之后恢复OpenGL状态

 void VowelCube::paintEvent(QPaintEvent * /* event */)

 {

     QPainter painter( this );

     //绘制背景

     drawBackground( &painter );

     //背景绘制结束

     painter.end( );

     //绘制立方体

     drawCube();

     //绘制开始

     painter.begin(this);

     //使用HTML文字设置QTextDocument对象

     drawLegend(&painter);

     painter.end( );

     swapBuffers( );

 }

 //鼠标按下事件

 void VowelCube::mousePressEvent(QMouseEvent *event)

 {

     lastPos = event->pos();

 }

 //鼠标移动事件

 void VowelCube::mouseMoveEvent(QMouseEvent *event)

 {

     GLfloat dx = GLfloat(event->x() - lastPos.x()) / width();

     GLfloat dy = GLfloat(event->y() - lastPos.y()) / height();

     if (event->buttons() & Qt::LeftButton) {

         rotationX +=  * dy;

         rotationY +=  * dx;

         update();

     } else if (event->buttons() & Qt::RightButton) {

         rotationX +=  * dy;

         rotationZ +=  * dx;

         update();

     }

     lastPos = event->pos();

 }

 //鼠标滚动的事件，调用update

 void VowelCube::wheelEvent(QWheelEvent *event)

 {

     double numDegrees = -event->delta() / 8.0;

     double numSteps = numDegrees / 15.0;

     scaling *= std::pow(1.125, numSteps);

     update();

 }

 //使用蓝色渐变色设置QRadialGradient

 void VowelCube::createGradient()

 {

     //确保指定的中心和焦点坐标根据窗口部件大小进行调整

     gradient.setCoordinateMode(QGradient::ObjectBoundingMode);

     //位置用0和1之间的浮点数表示，0对应焦点坐标，1对应圆的边缘

     gradient.setCenter(0.45, 0.50);

     gradient.setFocalPoint(0.40, 0.45);

     gradient.setColorAt(0.0, QColor(, , ));

     gradient.setColorAt(0.4, QColor(, , ));

     gradient.setColorAt(0.8, QColor(, , ));

 }

 //创建OpenGL列表，该列表保存绘制的立方体的边。

 void VowelCube::createGLObject()

 {

     makeCurrent();

     glShadeModel(GL_FLAT);

     glObject = glGenLists();

     glNewList(glObject, GL_COMPILE);

     qglColor(QColor(, , ));

     glLineWidth(1.0);

     glBegin(GL_LINES);

     glVertex3f(+1.0, +1.0, -1.0);

     glVertex3f(-1.0, +1.0, -1.0);

     glVertex3f(+1.0, -1.0, -1.0);

     glVertex3f(-1.0, -1.0, -1.0);

     glVertex3f(+1.0, -1.0, +1.0);

     glVertex3f(-1.0, -1.0, +1.0);

     glEnd();

     glBegin(GL_LINE_LOOP);

     glVertex3f(+1.0, +1.0, +1.0);

     glVertex3f(+1.0, +1.0, -1.0);

     glVertex3f(+1.0, -1.0, -1.0);

     glVertex3f(+1.0, -1.0, +1.0);

     glVertex3f(+1.0, +1.0, +1.0);

     glVertex3f(-1.0, +1.0, +1.0);

     glVertex3f(-1.0, +1.0, -1.0);

     glVertex3f(-1.0, -1.0, -1.0);

     glVertex3f(-1.0, -1.0, +1.0);

     glVertex3f(-1.0, +1.0, +1.0);

     glEnd();

     glEndList();

 }

 void VowelCube::drawBackground(QPainter *painter)

 {

     painter->setPen(Qt::NoPen);

     painter->setBrush(gradient);

     painter->drawRect(rect());

 }

 //绘制立方体

 void VowelCube::drawCube()

 {

     glPushAttrib(GL_ALL_ATTRIB_BITS);

     glMatrixMode(GL_PROJECTION);

     glPushMatrix();

     glLoadIdentity();

     GLfloat x = 3.0 * GLfloat(width()) / height();

     glOrtho(-x, +x, -3.0, +3.0, 4.0, 15.0);

     glMatrixMode(GL_MODELVIEW);

     glPushMatrix();

     glLoadIdentity();

     glTranslatef(0.0, 0.0, -10.0);

     glScalef(scaling, scaling, scaling);

     glRotatef(rotationX, 1.0, 0.0, 0.0);

     glRotatef(rotationY, 0.0, 1.0, 0.0);

     glRotatef(rotationZ, 0.0, 0.0, 1.0);

     //设置反走样

     glEnable(GL_MULTISAMPLE);

     //绘制立方体

     glCallList(glObject);

     //设置文字颜色和字体

     setFont(QFont("Times", ));

     qglColor(QColor(, , ));

     //绘制字符，renderText使文字不变形

     renderText(+1.1, +1.1, +1.1, QChar('a'));

     renderText(-1.1, +1.1, +1.1, QChar('e'));

     renderText(+1.1, +1.1, -1.1, QChar('o'));

     renderText(-1.1, +1.1, -1.1, QChar(0x00F6));

     renderText(+1.1, -1.1, +1.1, QChar(0x0131));

     renderText(-1.1, -1.1, +1.1, QChar('i'));

     renderText(+1.1, -1.1, -1.1, QChar('u'));

     renderText(-1.1, -1.1, -1.1, QChar(0x00FC));

     glMatrixMode(GL_MODELVIEW);

     glPopMatrix();

     glMatrixMode(GL_PROJECTION);

     glPopMatrix();

     glPopAttrib();

 }

 //使用HTML文字设置QTextDocument对象，在半透明的蓝色矩形上绘制它们

 void VowelCube::drawLegend(QPainter *painter)

 {

     const int Margin = ;

     const int Padding = ;

     QTextDocument textDocument;

     textDocument.setDefaultStyleSheet("* { color: #FFEFEF }");

     textDocument.setHtml("<h4 align=\"center\">Vowel Categories</h4>"

                          "<p align=\"center\"><table width=\"100%\">"

                          "<tr><td>Open:<td>a<td>e<td>o<td>&ouml;"

                          "<tr><td>Close:<td>ı<td>i<td>u<td>&uuml;"

                          "<tr><td>Front:<td>e<td>i<td>&ouml;<td>&uuml;"

                          "<tr><td>Back:<td>a<td>ı<td>o<td>u"

                          "<tr><td>Round:<td>o<td>&ouml;<td>u<td>&uuml;"

                          "<tr><td>Unround:<td>a<td>e<td>ı<td>i"

                          "</table>");

     textDocument.setTextWidth(textDocument.size().width());

     QRect rect(QPoint(, ), textDocument.size().toSize()

                              + QSize( * Padding,  * Padding));

     painter->translate(width() - rect.width() - Margin,

                        height() - rect.height() - Margin);

     painter->setPen(QColor(, , ));

     painter->setBrush(QColor(, , , ));

     painter->drawRect(rect);

     painter->translate(Padding, Padding);

     textDocument.drawContents(painter);

 }

巴特西

46.Qt 使用OpenGL绘制立方体

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