OpenGL实现二维图的平移

来源：互联网发布：淘宝投放手机详情编辑：程序博客网时间：2024/06/06 20:07

在前面的博客《OpenGL实现二维图的缩放》中，我提到了gluLookAt的作用是定义观察者的位置和视线方向。在本文中，我们正好利用这个功能来实现二维图的平移。

#ifndef WIDGET_H#define WIDGET_H#include <QGLWidget>#include <QWheelEvent>#include <QMouseEvent>class Widget : public QGLWidget{    Q_OBJECTpublic:    explicit Widget(QWidget *parent = 0);    ~Widget();    int           m_iWidth;    int           m_iHeight;    float           m_fXOffset;    float           m_fYOffset;    float           m_fPrevXPos;    float           m_fPrevYPos;    int             m_iXPos;    int             m_iYPos;    bool            m_bMoved;    int           m_iMag;private:protected:    virtual void initializeGL();    virtual void paintGL();    virtual void resizeGL(int, int);    virtual void wheelEvent(QWheelEvent *);    virtual void mouseMoveEvent(QMouseEvent *);    virtual void mousePressEvent(QMouseEvent *);    virtual void mouseReleaseEvent(QMouseEvent *);};#endif // WIDGET_H

#include "widget.h"#include <GL/glu.h>Widget::Widget(QWidget *parent) :    QGLWidget(parent){    setMouseTracking(false);    m_fPrevXPos = m_fPrevYPos = 0.0;    m_fXOffset = m_fYOffset = 0.0;    m_bMoved = false;}Widget::~Widget(){}void Widget::wheelEvent(QWheelEvent *e){    QPoint qpMag = e->angleDelta();    int iMag = qpMag.y();    bool bUpdate = false;    if(iMag > 0)    {        if(m_iMag < 8)        {            m_iMag *= 2;            bUpdate = true;        }    }    if(iMag < 0)    {        if(m_iMag > 1)        {            m_iMag /= 2;            bUpdate = true;        }    }    if(bUpdate)    {        updateGL();    }}void Widget::initializeGL(){    glClearColor(0.0, 1.0, 1.0, 0);    m_iMag = 1;}void Widget::resizeGL(int w, int h){    if(w > 0 && h >0)    {        glViewport(0, 0, (GLint)w, (GLint)h);//这句话把显示的范围跟glWindow范围划了等号        m_iWidth = w;        m_iHeight = h;    }}void Widget::paintGL(){    //clear放在初始化里面会造成闪烁    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);    glMatrixMode(GL_PROJECTION);    glLoadIdentity();    gluPerspective(10.0 * m_iMag, m_iWidth / m_iHeight, -8.0, 8.0);    glMatrixMode(GL_MODELVIEW);    glLoadIdentity();    gluLookAt(m_fPrevXPos + m_fXOffset * 0.01, m_fPrevYPos + m_fYOffset * 0.01, 50.0,              m_fPrevXPos + m_fXOffset * 0.01, m_fPrevYPos + m_fYOffset * 0.01, 0.0,              0.0, 1.0, 0.0);    glBegin(GL_QUADS);    glVertex2f(-0.5, -0.5);    glVertex2f(0.5, -0.5);    glVertex2f(0.5, 0.5);    glVertex2f(-0.5, 0.5);    glEnd();}void Widget::mouseMoveEvent(QMouseEvent *e){    if(m_bMoved)    {        m_fXOffset = m_iXPos - e->x();        m_fYOffset = e->y() - m_iYPos;//widget对Y方向的定义和opengl坐标系相反        updateGL();    }}void Widget::mouseReleaseEvent(QMouseEvent *e){    Q_UNUSED(e);    m_fPrevXPos += m_fXOffset * 0.01;    m_fPrevYPos += m_fYOffset * 0.01;    m_fXOffset = m_fYOffset = 0.0;    m_bMoved = false;}void Widget::mousePressEvent(QMouseEvent *e){    m_iXPos = e->x();    m_iYPos = e->y();    m_bMoved = true;}

运行程序，可见白色正方形随着鼠标拖动而移动

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