用OpenSceneGraph实现的NeHe OpenGL教程 - 第四十八课

• 简介

NeHe教程在这节课向我们介绍了轨迹球技术。轨迹球技术可以让用户使用鼠标直接旋转物体，这是所有交互式3D软件必须提供的最基本的功能。在OSG中已经提供了功能强大的漫游器，包括TrackballManipulator、FirstPersonManipulator、DriveManipulator等等，具体实现的代码可以参看osgGA库中的源码部分。

• 实现

首先创建场景中的两个几何体：

osg::Geode*createSphereGeode()osg::Geode*createTorusGeode(float MinorRadius, float MajorRadius)

将两者添加到场景根节点中

osg::MatrixTransform *torusMT = new osg::MatrixTransform;torusMT->setMatrix(osg::Matrix::translate(-1.5, 0.0, -6.0));torusMT->addChild(createTorusGeode(0.3,1.0));osg::MatrixTransform *sphereMT = new osg::MatrixTransform;sphereMT->setMatrix(osg::Matrix::translate(1.5, 0.0, -6.0));sphereMT->addChild(createSphereGeode());root->addChild(torusMT);root->addChild(sphereMT);

最后只需要添加一行代码，将漫游器添加到场景之中：

this->setCameraManipulator(new osgGA::TrackballManipulator);

编译运行程序：

附：本课源码（源码中可能存在着错误和不足之处，仅供参考）

#include "../osgNeHe.h"#include <QtCore/QTimer>#include <QtGui/QApplication>#include <QtGui/QVBoxLayout>#include <osgViewer/Viewer>#include <osgDB/ReadFile>#include <osgQt/GraphicsWindowQt>#include <osg/MatrixTransform>#include <osg/ShapeDrawable>#include <osgGA/TrackballManipulator>osg::Geode*createSphereGeode(){osg::Geode *sphereGeode = new osg::Geode;osg::ShapeDrawable *shapeDrawable = new osg::ShapeDrawable;shapeDrawable->setShape(new osg::Sphere(osg::Vec3(), 1.3));shapeDrawable->setColor(osg::Vec4(1.0f,0.75f,0.75f, 1.0f));sphereGeode->addDrawable(shapeDrawable);return sphereGeode;}osg::Geode*createTorusGeode(float MinorRadius, float MajorRadius){osg::Geode *geode = new osg::Geode;osg::Geometry *geometry = new osg::Geometry;osg::Vec3Array *vertexArray = new osg::Vec3Array;osg::Vec3Array *normalArray = new osg::Vec3Array;osg::Vec3Array *colorArray = new osg::Vec3Array;colorArray->push_back(osg::Vec3(0.75f,0.75f,1.0f));for (int i=0; i<20; i++ )// Stacks{for (int j=-1; j<20; j++)// Slices{float wrapFrac = (j%20)/(float)20;float phi = 2* osg::PI*wrapFrac;float sinphi = float(sin(phi));float cosphi = float(cos(phi));float r = MajorRadius + MinorRadius*cosphi;normalArray->push_back(osg::Vec3(float(sin(2* osg::PI*(i%20+wrapFrac)/(float)20))*cosphi, sinphi, float(cos(2* osg::PI*(i%20+wrapFrac)/(float)20))*cosphi));vertexArray->push_back(osg::Vec3(float(sin(2* osg::PI*(i%20+wrapFrac)/(float)20))*r,MinorRadius*sinphi,float(cos(2* osg::PI*(i%20+wrapFrac)/(float)20))*r));normalArray->push_back(osg::Vec3(float(sin(2* osg::PI*(i+1%20+wrapFrac)/(float)20))*cosphi, sinphi, float(cos(2* osg::PI*(i+1%20+wrapFrac)/(float)20))*cosphi));vertexArray->push_back(osg::Vec3(float(sin(2* osg::PI*(i+1%20+wrapFrac)/(float)20))*r,MinorRadius*sinphi,float(cos(2* osg::PI*(i+1%20+wrapFrac)/(float)20))*r));}}geometry->setVertexArray(vertexArray);geometry->setNormalArray(normalArray, osg::Array::BIND_PER_VERTEX);geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::TRIANGLE_STRIP, 0, vertexArray->size()));geode->addDrawable(geometry);return geode;}class ViewerWidget : public QWidget, public osgViewer::Viewer{public:ViewerWidget(osg::Node *scene = NULL){QWidget* renderWidget = getRenderWidget( createGraphicsWindow(0,0,100,100), scene);QVBoxLayout* layout = new QVBoxLayout;layout->addWidget(renderWidget);layout->setContentsMargins(0, 0, 0, 1);setLayout( layout );connect( &_timer, SIGNAL(timeout()), this, SLOT(update()) );_timer.start( 10 );}QWidget* getRenderWidget( osgQt::GraphicsWindowQt* gw, osg::Node* scene ){osg::Camera* camera = this->getCamera();camera->setGraphicsContext( gw );const osg::GraphicsContext::Traits* traits = gw->getTraits();camera->setClearColor( osg::Vec4(0.0, 0.0, 0.0, 1.0) );camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );camera->setProjectionMatrixAsPerspective(45.0f, static_cast<double>(traits->width)/static_cast<double>(traits->height), 0.1f, 100.0f );camera->setViewMatrixAsLookAt(osg::Vec3d(0, 0, 1), osg::Vec3d(0, 0, 0), osg::Vec3d(0, 1, 0));this->setSceneData( scene );//添加轨迹球this->setCameraManipulator(new osgGA::TrackballManipulator);return gw->getGLWidget();}osgQt::GraphicsWindowQt* createGraphicsWindow( int x, int y, int w, int h, const std::string& name="", bool windowDecoration=false ){osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();osg::ref_ptr<osg::GraphicsContext::Traits> 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();return new osgQt::GraphicsWindowQt(traits.get());}virtual void paintEvent( QPaintEvent* event ){ frame(); }protected:QTimer _timer;};osg::Node*buildScene(){osg::Group *root = new osg::Group;osg::MatrixTransform *torusMT = new osg::MatrixTransform;torusMT->setMatrix(osg::Matrix::translate(-1.5, 0.0, -6.0));torusMT->addChild(createTorusGeode(0.3,1.0));osg::MatrixTransform *sphereMT = new osg::MatrixTransform;sphereMT->setMatrix(osg::Matrix::translate(1.5, 0.0, -6.0));sphereMT->addChild(createSphereGeode());root->addChild(torusMT);root->addChild(sphereMT);return root;}int main( int argc, char** argv ){QApplication app(argc, argv);ViewerWidget* viewWidget = new ViewerWidget(buildScene());viewWidget->setGeometry( 100, 100, 640, 480 );viewWidget->show();return app.exec();}