glwidget.cpp Example File
^{opengl/grabber/glwidget.cpp}

    /****************************************************************************
    **
    ** Copyright (C) 2005-2006 Trolltech ASA. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
    ** http://www.trolltech.com/products/qt/licensing.html or contact the
    ** sales department at sales@trolltech.com.
    **
    ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
    **
    ****************************************************************************/

    #include <QtGui>
    #include <QtOpenGL>

    #include <math.h>

    #include "glwidget.h"

    GLWidget::GLWidget(QWidget *parent)
        : QGLWidget(parent)
    {
        gear1 = 0;
        gear2 = 0;
        gear3 = 0;
        xRot = 0;
        yRot = 0;
        zRot = 0;
        gear1Rot = 0;

        QTimer *timer = new QTimer(this);
        connect(timer, SIGNAL(timeout()), this, SLOT(advanceGears()));
        timer->start(20);
    }

    GLWidget::~GLWidget()
    {
        makeCurrent();
        glDeleteLists(gear1, 1);
        glDeleteLists(gear2, 1);
        glDeleteLists(gear3, 1);
    }

    void GLWidget::setXRotation(int angle)
    {
        normalizeAngle(&angle);
        if (angle != xRot) {
            xRot = angle;
            emit xRotationChanged(angle);
            updateGL();
        }
    }

    void GLWidget::setYRotation(int angle)
    {
        normalizeAngle(&angle);
        if (angle != yRot) {
            yRot = angle;
            emit yRotationChanged(angle);
            updateGL();
        }
    }

    void GLWidget::setZRotation(int angle)
    {
        normalizeAngle(&angle);
        if (angle != zRot) {
            zRot = angle;
            emit zRotationChanged(angle);
            updateGL();
        }
    }

    void GLWidget::initializeGL()
    {
        static const GLfloat lightPos[4] = { 5.0f, 5.0f, 10.0f, 1.0f };
        static const GLfloat reflectance1[4] = { 0.8f, 0.1f, 0.0f, 1.0f };
        static const GLfloat reflectance2[4] = { 0.0f, 0.8f, 0.2f, 1.0f };
        static const GLfloat reflectance3[4] = { 0.2f, 0.2f, 1.0f, 1.0f };

        glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
        glEnable(GL_LIGHTING);
        glEnable(GL_LIGHT0);
        glEnable(GL_DEPTH_TEST);

        gear1 = makeGear(reflectance1, 1.0, 4.0, 1.0, 0.7, 20);
        gear2 = makeGear(reflectance2, 0.5, 2.0, 2.0, 0.7, 10);
        gear3 = makeGear(reflectance3, 1.3, 2.0, 0.5, 0.7, 10);

        glEnable(GL_NORMALIZE);
    }

    void GLWidget::paintGL()
    {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glPushMatrix();
        glRotated(xRot / 16.0, 1.0, 0.0, 0.0);
        glRotated(yRot / 16.0, 0.0, 1.0, 0.0);
        glRotated(zRot / 16.0, 0.0, 0.0, 1.0);

        drawGear(gear1, -3.0, -2.0, 0.0, gear1Rot / 16.0);
        drawGear(gear2, +3.1, -2.0, 0.0, -2.0 * (gear1Rot / 16.0) - 9.0);

        glRotated(+90.0, 1.0, 0.0, 0.0);
        drawGear(gear3, -3.1, -1.8, -2.2, +2.0 * (gear1Rot / 16.0) - 2.0);

        glPopMatrix();
    }

    void GLWidget::resizeGL(int width, int height)
    {
        int side = qMin(width, height);
        glViewport((width - side) / 2, (height - side) / 2, side, side);

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glFrustum(-1.0, +1.0, -1.0, 1.0, 5.0, 60.0);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glTranslated(0.0, 0.0, -40.0);
    }

    void GLWidget::mousePressEvent(QMouseEvent *event)
    {
        lastPos = event->pos();
    }

    void GLWidget::mouseMoveEvent(QMouseEvent *event)
    {
        int dx = event->x() - lastPos.x();
        int dy = event->y() - lastPos.y();

        if (event->buttons() & Qt::LeftButton) {
            setXRotation(xRot + 8 * dy);
            setYRotation(yRot + 8 * dx);
        } else if (event->buttons() & Qt::RightButton) {
            setXRotation(xRot + 8 * dy);
            setZRotation(zRot + 8 * dx);
        }
        lastPos = event->pos();
    }

    void GLWidget::advanceGears()
    {
        gear1Rot += 2 * 16;
        updateGL();
    }

    GLuint GLWidget::makeGear(const GLfloat *reflectance, GLdouble innerRadius,
                              GLdouble outerRadius, GLdouble thickness,
                              GLdouble toothSize, GLint toothCount)
    {
        const double Pi = 3.14159265358979323846;

        GLuint list = glGenLists(1);
        glNewList(list, GL_COMPILE);
        glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, reflectance);

        GLdouble r0 = innerRadius;
        GLdouble r1 = outerRadius - toothSize / 2.0;
        GLdouble r2 = outerRadius + toothSize / 2.0;
        GLdouble delta = (2.0 * Pi / toothCount) / 4.0;
        GLdouble z = thickness / 2.0;
        int i, j;

        glShadeModel(GL_FLAT);

        for (i = 0; i < 2; ++i) {
            GLdouble sign = (i == 0) ? +1.0 : -1.0;

            glNormal3d(0.0, 0.0, sign);

            glBegin(GL_QUAD_STRIP);
            for (j = 0; j <= toothCount; ++j) {
                GLdouble angle = 2.0 * Pi * j / toothCount;
                glVertex3d(r0 * cos(angle), r0 * sin(angle), sign * z);
                glVertex3d(r1 * cos(angle), r1 * sin(angle), sign * z);
                glVertex3d(r0 * cos(angle), r0 * sin(angle), sign * z);
                glVertex3d(r1 * cos(angle + 3 * delta), r1 * sin(angle + 3 * delta),
                           sign * z);
            }
            glEnd();

            glBegin(GL_QUADS);
            for (j = 0; j < toothCount; ++j) {
                GLdouble angle = 2.0 * Pi * j / toothCount;
                glVertex3d(r1 * cos(angle), r1 * sin(angle), sign * z);
                glVertex3d(r2 * cos(angle + delta), r2 * sin(angle + delta),
                           sign * z);
                glVertex3d(r2 * cos(angle + 2 * delta), r2 * sin(angle + 2 * delta),
                           sign * z);
                glVertex3d(r1 * cos(angle + 3 * delta), r1 * sin(angle + 3 * delta),
                           sign * z);
            }
            glEnd();
        }

        glBegin(GL_QUAD_STRIP);
        for (i = 0; i < toothCount; ++i) {
            for (j = 0; j < 2; ++j) {
                GLdouble angle = 2.0 * Pi * (i + (j / 2.0)) / toothCount;
                GLdouble s1 = r1;
                GLdouble s2 = r2;
                if (j == 1)
                    qSwap(s1, s2);

                glNormal3d(cos(angle), sin(angle), 0.0);
                glVertex3d(s1 * cos(angle), s1 * sin(angle), +z);
                glVertex3d(s1 * cos(angle), s1 * sin(angle), -z);

                glNormal3d(s2 * sin(angle + delta) - s1 * sin(angle),
                           s1 * cos(angle) - s2 * cos(angle + delta), 0.0);
                glVertex3d(s2 * cos(angle + delta), s2 * sin(angle + delta), +z);
                glVertex3d(s2 * cos(angle + delta), s2 * sin(angle + delta), -z);
            }
        }
        glVertex3d(r1, 0.0, +z);
        glVertex3d(r1, 0.0, -z);
        glEnd();

        glShadeModel(GL_SMOOTH);

        glBegin(GL_QUAD_STRIP);
        for (i = 0; i <= toothCount; ++i) {
            GLdouble angle = i * 2.0 * Pi / toothCount;
            glNormal3d(-cos(angle), -sin(angle), 0.0);
            glVertex3d(r0 * cos(angle), r0 * sin(angle), +z);
            glVertex3d(r0 * cos(angle), r0 * sin(angle), -z);
        }
        glEnd();

        glEndList();

        return list;
    }

    void GLWidget::drawGear(GLuint gear, GLdouble dx, GLdouble dy, GLdouble dz,
                            GLdouble angle)
    {
        glPushMatrix();
        glTranslated(dx, dy, dz);
        glRotated(angle, 0.0, 0.0, 1.0);
        glCallList(gear);
        glPopMatrix();
    }

    void GLWidget::normalizeAngle(int *angle)
    {
        while (*angle < 0)
            *angle += 360 * 16;
        while (*angle > 360 * 16)
            *angle -= 360 * 16;
    }