OpenSceneGraph实现的NeHe OpenGL教程 - 第四十八课

来源：互联网发布：ubuntu terminal替换编辑：程序博客网时间：2024/06/06 12:30

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：

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

将两者添加到场景根节点中

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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：

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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）

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#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();  
}  

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OpenSceneGraph实现的NeHe OpenGL教程 - 第四十八课

简介

实现