OSG学习：场景图形管理（三）——多视图相机渲染

ゝ一纸荒年。 2022-05-18 02:59 179阅读 0赞

> 以下内容来自： 
> 
> 1、《OpenSceneGraph三维渲染引擎编程指南》肖鹏 刘更代 徐明亮 清华大学出版社 
> 
> 2、《OpenSceneGraph三维渲染引擎设计与实践》王锐 钱学雷 清华大学出版社
> 
> 3、自己的总结

> [下载完整工程OSG\_18\_MultipleViewCameras][OSG_18_MultipleViewCameras]
> 
> 创建C++项目后，首先需要配置OSG环境，具体步骤看[OSG学习：WIN10系统下OSG+VS2017编译及运行][OSG_WIN10_OSG_VS2017]第六步：新建OSG项目测试。

// stdafx.h
     
    #include <osg/Node>
    #include <osg/Geode>  
    #include <osg/Geometry>
    #include <osg/Group>
     
    #include <osg/MatrixTransform> //移动节点的矩阵类，最常用的移动节点的类。可随动、旋转控制节点
    #include <osg/PositionAttitudeTransform> //位置变换节点类，提供模型的位置变换、大小缩放、原点位置的设置、坐标系的变换
    #include <osg/Camera>  //相机节点，管理OSG中的模型——视图矩阵，相机的管理主要是通过各种变换实现的
     
    #include <osgGA/TrackballManipulator> 
     
    #include <osgDB/ReadFile>
    #include <osgDB/WriteFile>
     
    #include <osgUtil/Optimizer>
    #include <osgViewer/Viewer>
    #include <osgViewer/ViewerEventHandlers> //事件监听
    #include <osgViewer/CompositeViewer>

//.cpp
     
    /*
    *多视图相机渲染
    *
    *在OSG中，多视图的管理是通过osgViewer::CompositeViewer来实现的，它负责多个视图的管理及同步工作，继承自osgViewer::ViewerBase类
    *
    *视图的创建：
    *设置图形环境特性
    *创建图形环境特性
    *创建视图
    *设置视图场景数据
    *（根据分辨率确定合适的投影来保证显示的图形不变形）
    *设置相机视口及图形环境
    *设置操作器
    *（添加事件处理）
    */
     
     
    osg::ref_ptr<osg::GraphicsContext> CreateGraphicsContext(osg::ref_ptr<osg::GraphicsContext::Traits> traits)
    {
    	//设置图形环境特性
    	//osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits();
    	traits->x = 100;
    	traits->y = 100;
    	traits->width = 900;
    	traits->height = 700;
    	traits->windowDecoration = true;
    	traits->doubleBuffer = true;
    	traits->sharedContext = 0;
     
    	//创建图形环境特性
    	osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext(traits.get());
    	if (gc->valid())
    	{
    		osg::notify(osg::INFO) << "GraphicsWindow has been created successfully." << std::endl;
     
    		//清除窗口颜色及颜色和深度缓冲
    		gc->setClearColor(osg::Vec4f(0.2f, 0.2f, 1.6f, 1.0f));
    		gc->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    	}
    	else
    	{
    		osg::notify(osg::NOTICE) << "GraphicsWindow has not been created successfully." << std::endl;
    	}
     
    	return gc.get();
    }
     
    //视图一
    void View1(osg::ref_ptr<osgViewer::CompositeViewer> viewer, osg::ref_ptr<osg::Node> node, osg::ref_ptr<osg::GraphicsContext::Traits> traits, osg::ref_ptr<osg::GraphicsContext> gc)
    {
    	//创建视图一
    	osg::ref_ptr<osgViewer::View> view = new osgViewer::View();
    	viewer->addView(view.get());
     
    	//设置视图场景数据
    	view->setSceneData(node.get());
     
    	//设置相机视口及图形环境
    	view->getCamera()->setViewport(new osg::Viewport(0, 0, traits->width / 2, traits->height / 2));
    	view->getCamera()->setGraphicsContext(gc.get());
     
    	//设置操作器
    	view->setCameraManipulator(new osgGA::TrackballManipulator);
     
    	//添加事件处理
    	view->addEventHandler(new osgViewer::StatsHandler);
    	view->addEventHandler(new osgViewer::WindowSizeHandler);
    	view->addEventHandler(new osgViewer::ThreadingHandler);
    	view->addEventHandler(new osgViewer::RecordCameraPathHandler);
    }
     
    //视图二
    void View2(osg::ref_ptr<osgViewer::CompositeViewer> viewer, osg::ref_ptr<osg::Node> node, osg::ref_ptr<osg::GraphicsContext::Traits> traits, osg::ref_ptr<osg::GraphicsContext> gc)
    {
    	//创建视图二
    	osg::ref_ptr<osgViewer::View> view = new osgViewer::View();
    	viewer->addView(view.get());
     
    	//设置视图场景数据
    	view->setSceneData(node.get());
     
    	//设置相机视口及图形环境
    	view->getCamera()->setViewport(new osg::Viewport(traits->width / 2, 0, traits->width / 2, traits->height / 2));
    	view->getCamera()->setGraphicsContext(gc.get());
    	
    	//设置操作器
    	view->setCameraManipulator(new osgGA::TrackballManipulator);
    }
     
    //视图三
    void View3(osg::ref_ptr<osgViewer::CompositeViewer> viewer, osg::ref_ptr<osg::Node> node, osg::ref_ptr<osg::GraphicsContext::Traits> traits, osg::ref_ptr<osg::GraphicsContext> gc)
    {
    	//创建视图三
    	osg::ref_ptr<osgViewer::View> view = new osgViewer::View();
    	viewer->addView(view.get());
     
    	//设置视图场景数据
    	view->setSceneData(node.get());
     
    	//根据分辨率确定合适的投影来保证显示的图形不变形
    	double fovy, aspectRatio, zNear, zFar;
    	view->getCamera()->getProjectionMatrixAsPerspective(fovy, aspectRatio, zNear, zFar);
    	double newAspectRatio = double(traits->width) / double(traits->height / 2);
    	double aspectRatioChange = newAspectRatio / aspectRatio;
    	if (aspectRatioChange != 1.0)
    	{
    		view->getCamera()->getProjectionMatrix() *= osg::Matrix::scale(1.0 / aspectRatioChange, 1.0, 1.0);
    	}
     
    	//设置相机视口及图形环境
    	view->getCamera()->setViewport(new osg::Viewport(0, traits->height / 2, traits->width / 2, traits->height / 2));
    	view->getCamera()->setGraphicsContext(gc.get());
    	
    	//设置操作器
    	view->setCameraManipulator(new osgGA::TrackballManipulator);
    }
     
    int main()
    {
    	//读取模型
    	osg::ref_ptr<osg::Node> cow = osgDB::readNodeFile("cow.osg");
    	osg::ref_ptr<osg::Node> cessna = osgDB::readNodeFile("cessna.osg");
     
    	//优化场景数据
    	osgUtil::Optimizer optimizer;
    	optimizer.optimize(cow.get());
    	optimizer.optimize(cessna.get());
     
    	//设置并创建图形环境
    	osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits();
    	osg::ref_ptr<osg::GraphicsContext> gc = CreateGraphicsContext(traits);
     
    	//创建CompositeViewer对象
    	osg::ref_ptr<osgViewer::CompositeViewer> viewer = new osgViewer::CompositeViewer();
    	View1(viewer, cow.get(), traits.get(), gc.get());
    	View2(viewer, cessna.get(), traits.get(), gc.get());
    	View3(viewer, cessna.get(), traits.get(), gc.get());
     
    	viewer->realize();
     
    	return viewer->run();
    }

![70][]

[OSG_18_MultipleViewCameras]: https://github.com/Epulari/osg-exercise
[OSG_WIN10_OSG_VS2017]: https://blog.csdn.net/u013719339/article/details/78415685
[70]: /images/20220518/f3db0fd1ae9e474393ffc0683c21a99e.png