[osg-users] problem zooming using mouse middle scroll in trackballmanipulator

[Srikanth Bemineni]

I am experimenting with the osgQTviewer.I am not able to zoom in when 
the mouse wheel is scrolled.I am using trackballmanipulator.I am not 
able to find a good documentation about camera manipulators.Even the 
Reference doc doesn't mention the explanation of manipulators.

AdapterWidget::AdapterWidget( ViewerQT *source ,QWidget * parent, const 
char * name, const QGLWidget * shareWidget, WindowFlags f):
#if USE_QT4
    QGLWidget(parent, shareWidget, f)
#else
    QGLWidget(parent, name, shareWidget, f)
#endif
{
    m_source = source;
    resize( 800 ,600 );
    /* To Remove this */
    /*
     * // create the window to draw to.
     * */
    osg::ref_ptr<osg::GraphicsContext::Traits> traits = new 
osg::GraphicsContext::Traits;
    traits->x = 200;
    traits->y = 200;
    traits->width = 800;
    traits->height = 600;
    traits->windowDecoration = true;
    traits->doubleBuffer = true;
    traits->sharedContext = 0;

    osg::ref_ptr<osg::GraphicsContext> gc = 
osg::GraphicsContext::createGraphicsContext(traits.get());
  

    _gw = new osgViewer::GraphicsWindowEmbedded(traits.get());
#if USE_QT4
    setFocusPolicy(Qt::ClickFocus);
#else
    setFocusPolicy(QWidget::ClickFocus);
#endif
}
..
... all the other event handling
...



void AdapterWidget::mouseMoveEvent( QMouseEvent* event )
{
    _gw->getEventQueue()->mouseMotion(event->x(), event->y());
}

void AdapterWidget::wheelEvent( QWheelEvent *event )
{
    //m_source->wheelEvent( event );
   
    if( event->delta() > 0 )
      _gw->getEventQueue()->mouseScroll(osgGA::GUIEventAdapter::SCROLL_UP );
    else
      
_gw->getEventQueue()->mouseScroll(osgGA::GUIEventAdapter::SCROLL_DOWN );
   
   
}

ViewerQT::
ViewerQT(QWidget * parent, const char * name, const QGLWidget * 
shareWidget , WindowFlags f ):
    AdapterWidget( this , parent, name, shareWidget, f )
    {

    znear = 1.0f;
    zfar = 10000.0f;
    getCamera()->setViewport(new osg::Viewport(0,0,width(),height()));
   
    //getCamera()->setProjectionMatrixAsPerspective(30.0f, 
static_cast<double>(width())/static_cast<double>(height()), 1.0f, 10000.0f);


    getCamera()->setGraphicsContext(getGraphicsWindow());
    /* To Remove*/
    osg::ref_ptr<osgGA::StateSetManipulator> statesetManipulator = new 
osgGA::StateSetManipulator(getCamera()->getStateSet());
    addEventHandler(statesetManipulator.get());
    /*to remove end*/

    addEventHandler(new PickHandler());

    setThreadingModel(osgViewer::Viewer::SingleThreaded);

    connect(&_timer, SIGNAL(timeout()), this, SLOT(updateGL()));
    _timer.start(10);
   
    _manipulator = new osgGA::TrackballManipulator;
    setCameraManipulator(_manipulator);
    cout<<"Minimum distance "<<_manipulator->getMinimumDistance()<<endl;
    cout<<"Homepostion 
compute"<<_manipulator->getAutoComputeHomePosition()<<endl;
    //_manipulator->setAutoComputeHomePosition(false);
    _manipulator->setMinimumDistance(1000);
    osg::Vec3d eye;
    osg::Vec3d center;
    osg::Vec3d up;
    _manipulator->getHomePosition( eye , center , up );
    cout<<"x y z "<< eye.x()<<eye.y()<<eye.z()<<endl;
    cout<<"x y z "<< center.x()<<center.y()<<center.z()<<endl;
    cout<<"x y z "<< up.x()<<up.y()<<up.z()<<endl;
   
}
       
void
ViewerQT::
VwheelEvent( QWheelEvent *event )
{

    cout<<event->delta()<<endl;
    if( event->delta() > 0 )
    {
        znear = znear + 120.0f;
    }
    else
    {
        if( (znear - 120) >= 1.0 )
        {
            znear = znear - 120;
        }
    }

}

void
ViewerQT::
paintGL()
{
    osg::Vec3d eye;
    osg::Vec3d center;
    osg::Vec3d up;
    _manipulator->getHomePosition( eye , center , up );
    cout<<"eye x y z "<< eye.x()<<" "<<eye.y()<<" "<<eye.z()<<endl;
    cout<<"center x y z "<<center.x()<<" "<<center.y()<<" 
"<<center.z()<<endl;
    cout<<"up x y z "<< up.x()<<" "<<up.y()<<" "<<up.z()<<endl;
    frame();
}


and this is how I am creating the Viewer window.
I tried to move the perspective view.
I tried to translate the camera matrix.
I tried to set the home positon
but none of the above things seems to work in moving the camera or 
zooming.I am new to opengl and open scene graph any guide would be 
really helpful.

Thank You

-- 
With Regards
Srikanth Bemineni
Geotrace Technologies
281-497-8440 extn 228