OSG多屏显示问题

// testMultiScreen.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <osg/Camera>
#include <osgDB/ReadFile>
#include <osgGA/TrackballManipulator>
#include <osgViewer/CompositeViewer>

osgViewer::View* createView( int screenNum )
{

unsigned int width = 800, height = 600;

//判断了当前是否存在窗体接口
 osg::GraphicsContext::WindowingSystemInterface* wsi = osg::GraphicsContext::getWindowingSystemInterface();
 if ( wsi )
 wsi->getScreenResolution( osg::GraphicsContext::ScreenIdentifier(screenNum), width, height );
//创建Traits

osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
 traits->screenNum = screenNum;
 traits->x = 0;
 traits->y = 0;
 traits->width = width;
 traits->height = height;
 traits->windowDecoration = false;
 traits->doubleBuffer = true;
 traits->sharedContext = 0;

//创建一个图形上下文

osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext( traits.get() );
 if ( !gc ) return NULL;
 osg::ref_ptr<osg::Camera> camera = new osg::Camera;
 camera->setGraphicsContext( gc.get() );
 camera->setViewport( new osg::Viewport(0, 0, width, height) );
 camera->setProjectionMatrixAsPerspective(30.0f, static_cast<double>(width)/static_cast<double>(height),1.0f, 10000.0f );
 GLenum buffer = traits->doubleBuffer ? GL_BACK : GL_FRONT;
 camera->setDrawBuffer( buffer );
 camera->setReadBuffer( buffer );

osg::ref_ptr<osgViewer::View> view = new osgViewer::View;
 view->setCamera( camera.get() );
 view->setCameraManipulator( new osgGA::TrackballManipulator );
 return view.release();
}

int _tmain(int argc, _TCHAR* argv[])
{
 osgViewer::CompositeViewer viewer;

osgViewer::View* view1 = createView( 0 );
 if ( view1 )
 {
  view1->setSceneData( osgDB::readNodeFile("cessna.osg") );
  viewer.addView( view1 );
 }

osgViewer::View* view2 = createView( 1 );
 if ( view2 )
 {
  view2->setSceneData( osgDB::readNodeFile("cow.osg") );
  viewer.addView( view2 );
 }

return viewer.run();

}