OpenSceneGraph中osgDB.PropByValSerializer的使用指南

概述

osgDB.PropByValSerializer是OpenSceneGraph中的一个序列化工具类，它可以将场景图节点的属性序列化成一个字符串，并保存到文件中。这个字符串可以被反序列化成节点的属性。

用法

下面是osgDB.PropByValSerializer主要的使用方法：

1. 包含头文件：

   #include <osgDB/PropByValSerializer>
   

2. 创建一个PropByValSerializer对象

   osgDB::PropByValSerializer serializer;
   

3. 将一个节点的属性序列化成一个字符串：

   std::string propString;
   osg::ref_ptr<osg::Node> node;
   node->getUserData()->write(serializer);
   propString = serializer.getString();
   

4. 将序列化后的字符串反序列化到一个节点的属性中：

   osg::ref_ptr<osg::Node> node;
   std::string propString;
   node->getUserData()->read(serializer);
   const char* propStringPtr = propString.c_str();
   serializer.readString(node->getOrCreateUserData(), propStringPtr);
   

5. 将序列化后的字符串保存到文件中：

   std::ofstream outfile("propString.dat", std::ios::binary);
   outfile.write(propString.c_str(), propString.size());
   outfile.close();
   

示例

下面是一个简单的例子，演示了如何使用osgDB.PropByValSerializer。

#include <osg/Group>
#include <osgDB/WriteFile>
#include <osgDB/FileUtils>
#include <osgDB/PropByValSerializer>

int main()
{
    osg::ref_ptr<osg::Group> root = new osg::Group;
    root->setUserData(new osg::UserData);

    osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array;
    vertices->push_back(osg::Vec3(0, 0, 0));
    vertices->push_back(osg::Vec3(1, 0, 0));
    vertices->push_back(osg::Vec3(0, 1, 0));

    osg::ref_ptr<osg::Geode> geode = new osg::Geode;
    geode->setUserValue("color", osg::Vec4(1.0f, 1.0f, 0.0f, 1.0f));
    {
        osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry;
        geometry->setVertexArray(vertices);

        osg::ref_ptr<osg::DrawElementsUInt> indices = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);
        indices->push_back(0);
        indices->push_back(1);
        indices->push_back(2);

        geometry->addPrimitiveSet(indices);

        geode->addDrawable(geometry);
    }

    root->addChild(geode);

    // 将节点的属性序列化成一个字符串
    osgDB::PropByValSerializer serializer;
    root->getUserData()->write(serializer);
    std::string propString = serializer.getString();

    // 将序列化后的字符串保存到文件中
    std::ofstream outfile("propString.dat", std::ios::binary);
    outfile.write(propString.c_str(), propString.size());
    outfile.close();

    // 将序列化后的字符串反序列化到一个节点的属性中
    osg::ref_ptr<osg::Group> root2 = new osg::Group;
    root2->setUserData(new osg::UserData);

    osg::ref_ptr<osgDB::ReaderWriter::Options> options = new osgDB::ReaderWriter::Options;
    std::string filename = "propString.dat";
    std::string extension = osgDB::getLowerCaseFileExtension(filename);
    osg::ref_ptr<osgDB::ReaderWriter> rw = osgDB::Registry::instance()->getReaderWriterForExtension(extension, options.get());
    osgDB::ReaderWriter::ReadResult rr = rw->readNodeFile(filename, options.get());
    if (rr.validNode())
    {
        root2->addChild(rr.getNode());
    }
    else
    {
        std::cout << "Could not load node from file: " << filename << std::endl;
    }

    const char* propStringPtr = propString.c_str();
    serializer.readString(root2->getOrCreateUserData(), propStringPtr);

    return osgDB::writeNodeFile(*root2, "propString.osgt");
}

参考资料

OpenSceneGraph 3.6.5 Documentation

• https://openthreads.github.io/documentation/classosgDB_1_1PropByValSerializer.html