OSG例程(3) 利用更新回调制作路径动画

OSG程序设计教程 第七章 

#include <osg/MatrixTransform>
#include <osg/PositionAttitudeTransform>
#include <osg/Geode>
#include <osgDB/Registry>
#include <osgDB/ReadFile>
#include <osgGA/TrackballManipulator>
#include <osgViewer/Viewer>

// create a animation path
osg::AnimationPath * createAnimationPath(const osg::Vec3 &center, float radius,double looptime)
{
    // declare animation path
    osg::AnimationPath * animationPath = new osg::AnimationPath;
    // set loop
    animationPath->setLoopMode(osg::AnimationPath::LOOP);
    // set the number of control points
    int numSamples = 40;
    float yaw = 0.0f;
    float yaw_delta = 2.0f * osg::PI/((float)numSamples - 1.0f);
    float roll = osg::inDegrees(30.0f);
    // set interval between control points
    double time = 0.0f;
    double time_delta = looptime/(double)numSamples;
    // insert cocntrol points
    for (int i=0; i< numSamples; ++i)
    {
        osg::Vec3 position(0,0,0);
        osg::Quat rotation( osg::Quat(roll, osg::Vec3(0.0,1.0,0.0)) * osg::Quat(-(yaw+osg::inDegrees(90.0f)), osg::Vec3(0.0,0.0,1.0)) );
        animationPath->insert(time, osg::AnimationPath::ControlPoint(position,rotation));
        yaw += yaw_delta;
        time += time_delta;
    }
    return animationPath;
}

osg::Node * createMovingModel(const osg::Vec3 &center,float radius)
{
    float animationLength = 10.0f;
    // animation path
    osg::AnimationPath *animationPath =  createAnimationPath(center,radius,animationLength);
    osg::Group * model = new osg::Group;
    // read model, and hide the first child node
    osg::Node * fountain = osgDB::readNodeFile("fountain.osg");
    fountain->asGroup()->getChild(0)->setNodeMask(0);
    // if fountain, update its nanimation path
    if (fountain)
    {
        osg::PositionAttitudeTransform *xform = new osg::PositionAttitudeTransform;
        // set update callback
        xform->setUpdateCallback(new osg::AnimationPathCallback(animationPath,0.0,1.0));
        // add children node
        xform->addChild(fountain);
        model->addChild(xform);
    }
    return model;
}

osg::Node * createModel()
{
    osg::Vec3 center(0.0f,0.0f,0.0f);
    float radius = 1.0f;
    osg::Group *root = new osg::Group;
    // create moving node, with radius
    osg::Node *movingModel = createMovingModel(center, radius *0.8f);
    // add node to root
    root->addChild(movingModel);
    return root;
}


int main()
{

    osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();

    viewer->setSceneData(createModel());
    viewer->setCameraManipulator(new osgGA::TrackballManipulator());

    viewer->realize();
    viewer->run();

}

TrackballManipulator貌似没有用。