osgEarth嵌入QT的QWidget

一直比较推崇QT这个界面库，所以打算把osg嵌入到QT里面做一个QWidget的子控件。
在查阅了官方的osgViewerQT后，决定写一个子类，同时继承osgViewer::Viewer和QGLWidget，用一个Widget来显示osg的单Viewer的场景。

class OsgQtWidget : public QGLWidget, public osgViewer::Viewer

{

Q_OBJECT

public:

OsgQtWidget(QWidget *parent = 0, const QGLWidget * shareWidget = 0, Qt::WFlags flags = 0);

OsgQtWidget(osgViewer::ViewerBase::ThreadingModel threadingModel = osgViewer::Viewer::SingleThreaded);

~OsgQtWidget();

void setScene();

osg::Camera* createCamera( int x, int y, int w, int h, const std::string& name="", bool windowDecoration=false );

virtual void paintGL();

private:

protected:

QTimer timer;

};

其中setScene()的关键代码

osg::Camera *camera = new osg::Camera();

camera = createCamera(0,0,100,100); //创建一个相机，具体实现见下文

this->setCamera( camera );  //使用上述相机

this->setSceneData( osgDB::readNodeFile("feature_geom.earth") ); //加载场景

this->addEventHandler( new osgViewer::StatsHandler );

this->setCameraManipulator( new osgEarth::Util::EarthManipulator() );  //设置漫游器为osgearth的漫游器

//将相机中管理的图形设备提供给QGLWidget当一个部件。

osgQt::GraphicsWindowQt* gw = dynamic_cast( camera->getGraphicsContext() );

QWidget* widget1 = gw->getGLWidget();

QGridLayout* grid = new QGridLayout;

grid->addWidget( widget1, 0, 0 );

this->setLayout( grid );

//通过定义一个Timer使QWidge实时（每10毫秒）更新窗口，也即触发paintGL事件，在paintGL事件中，调用frame方法来重绘帧。

connect( &timer, SIGNAL(timeout()), this, SLOT(update()) );

timer.start( 10 );

 

createCarema的代码

如上图所示，在一个Viewer中，相机拍摄的内容是用图形设备（GraphicsContext）做为载体来显示渲染结果

osg::Camera* OsgQtWidget::createCamera( int x, int y, int w, int h, const std::string& name, bool windowDecoration)

{

        osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();
        //定义渲染窗口的属性此窗口可以被各个平台实现。

        osg::ref_ptr traits = new osg::GraphicsContext::Traits;

        traits->windowName = name;

        traits->windowDecoration = windowDecoration;

        traits->x = x;

        traits->y = y;

        traits->width = w;

        traits->height = h;

        traits->doubleBuffer = true;

        traits->alpha = ds->getMinimumNumAlphaBits();

        traits->stencil = ds->getMinimumNumStencilBits();

        traits->sampleBuffers = ds->getMultiSamples();

        traits->samples = ds->getNumMultiSamples();

        

        osg::ref_ptr camera = new osg::Camera;

        camera->setGraphicsContext( new osgQt::GraphicsWindowQt(traits.get()) );

        
       //设置相机所看到的背景颜色

        camera->setClearColor( osg::Vec4(0.2, 0.2, 0.6, 1.0) );

        //设置视口

        camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );
        //设置投影矩阵为透视投影

        camera->setProjectionMatrixAsPerspective(

            30.0f, static_cast(traits->width)/static_cast(traits->height), 1.0f, 10000.0f );

        return camera.release();

}