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# glwidget.cpp Example File
opengl/grabber/glwidget.cpp

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        #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;
        }