Drawing a cube

Hi all,

I have this code based in this another code to draw a cube:

Code:

---

#-------------------------------------------------
#
# Project created by QtCreator 2012-05-28T13:03:04
#
#-------------------------------------------------
 
QT       += core gui opengl
 
TARGET = opengl
TEMPLATE = app
 
 
SOURCES += main.cpp \
    cube.cpp
 
HEADERS  += cube.h

---

Code:

---

#include <QtGui/QApplication>
#include "cube.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    if (!QGLFormat::hasOpenGL())
        qFatal("This system has no OpenGL support");
    Cube cube;
    cube.resize(300, 300);
    cube.show();
    return app.exec();
}

---

Code:

---

#ifndef GLWIDGET_H
#define GLWIDGET_H
 
#include <QGLWidget>
#include <QMouseEvent>
 
class Cube : public QGLWidget
{
public:
    Cube(QWidget *parent = 0);
protected:
    void initializeGL();
    void resizeGL(int width, int height);
    void paintGL();
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mouseDoubleClickEvent(QMouseEvent *event);
private:
    void draw();
    int faceAtPosition(const QPoint &pos);
    GLfloat rotationX;
    GLfloat rotationY;
    GLfloat rotationZ;
    QColor faceColors[6];
    QPoint lastPos;
};
 
#endif // GLWIDGET_H

---

Code:

---

#include "cube.h"
#include <QColorDialog>
#include <GL/glu.h>
 
Cube::Cube(QWidget *parent)
: QGLWidget(parent)
{
    setFormat(QGLFormat(QGL::DoubleBuffer | QGL::DepthBuffer));
    rotationX = 0;
    rotationY = 0;
    rotationZ = 0;
    faceColors[0] = Qt::red;
    faceColors[1] = Qt::green;
    faceColors[2] = Qt::blue;
    faceColors[3] = Qt::cyan;
    faceColors[4] = Qt::yellow;
    faceColors[5] = Qt::magenta;
}
 
void Cube::initializeGL()
{
    qglClearColor(Qt::black);
    glShadeModel(GL_FLAT);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
}
 
void Cube::resizeGL(int width, int height)
{
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    GLfloat x = (GLfloat)width / height;
    glFrustum(-x, x, -1.0, 1.0, 4.0, 15.0);
    glMatrixMode(GL_MODELVIEW);
}
 
void Cube::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    draw();
}
 
void Cube::draw()
{
    static const GLfloat coords[6] [4] [3] = {
        { { +1.0, -1.0, +1.0 }, { +1.0, -1.0, -1.0 },
        { +1.0, +1.0, -1.0 }, { +1.0, +1.0, +1.0 } },
        { { -1.0, -1.0, -1.0 }, { -1.0, -1.0, +1.0 },
        { -1.0, +1.0, +1.0 }, { -1.0, +1.0, -1.0 } },
        { { +1.0, -1.0, -1.0 }, { -1.0, -1.0, -1.0 },
        { -1.0, +1.0, -1.0 }, { +1.0, +1.0, -1.0 } },
        { { -1.0, -1.0, +1.0 }, { +1.0, -1.0, +1.0 },
        { +1.0, +1.0, +1.0 }, { -1.0, +1.0, +1.0 } },
        { { -1.0, -1.0, -1.0 }, { +1.0, -1.0, -1.0 },
        { +1.0, -1.0, +1.0 }, { -1.0, -1.0, +1.0 } },
        { { -1.0, +1.0, +1.0 }, { +1.0, +1.0, +1.0 },
        { +1.0, +1.0, -1.0 }, { -1.0, +1.0, -1.0 } }
    };
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -10.0);
    glRotatef(rotationX, 1.0, 0.0, 0.0);
    glRotatef(rotationY, 0.0, 1.0, 0.0);
    glRotatef(rotationZ, 0.0, 0.0, 1.0);
    for (int i = 0; i < 6; ++i) {
        glLoadName(i);
        glBegin(GL_QUADS);
        qglColor(faceColors[i]);
        for (int j = 0; j < 4; ++j) {
            glVertex3f(coords[i] [j] [0], coords[i] [j] [1],
            coords[i] [j] [2]);
        }
        glEnd();
    }
}
 
void Cube::mousePressEvent(QMouseEvent *event)
{
    lastPos = event->pos();
}
 
void Cube::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 += 180 * dy;
        rotationY += 180 * dx;
        updateGL();
    } else if (event->buttons() & Qt::RightButton) {
        rotationX += 180 * dy;
        rotationZ += 180 * dx;
        updateGL();
    }
    lastPos = event->pos();
}
 
void Cube::mouseDoubleClickEvent(QMouseEvent *event)
{
    int face = faceAtPosition(event->pos());
    if (face != -1) {
        QColor color = QColorDialog::getColor(faceColors[face],
        this);
        if (color.isValid()) {
            faceColors[face] = color;
            updateGL();
        }
    }
}
 
int Cube::faceAtPosition(const QPoint &pos)
{
    const int MaxSize = 512;
    GLuint buffer[MaxSize];
    GLint viewport[4];
    glGetIntegerv(GL_VIEWPORT, viewport);
    glSelectBuffer(MaxSize, buffer);
    glRenderMode(GL_SELECT);
    glInitNames();
    glPushName(0);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    gluPickMatrix((GLdouble)pos.x(),
    (GLdouble) (viewport[3] - pos.y()),
    5.0, 5.0, viewport);
    GLfloat x = (GLfloat)width() / height();
    glFrustum(-x, x, -1.0, 1.0, 4.0, 15.0);
    draw();
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    if (!glRenderMode(GL_RENDER))
        return -1;
    return buffer[3];
}

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There are any native implementation in Qt C++ that encapsulates all of this to simplify the 3D usage? I think that the above code is a very low level code to draw a cube. I have used Ogre in Qt and it's simplify a bit the 3D usage.

Regards.

See your earlier thread