osg_输出场景中的顶点

事实上不仅是绘制的图形有顶点，模型也是有顶点的

接下来用visitor取顶点，visitor和回调有所区别的是visitor是直接调用，不需要开始渲染就可以完成计算。

class VertexExtractor : public osg::NodeVisitor
{
public:
	osg::ref_ptr extracted_verts;
	VertexExtractor() : osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN)
	{
		extracted_verts = new osg::Vec3Array;
	}

	void apply(osg::Geode& geode)
	{
		for (int i = 0; i < geode.getNumDrawables(); i++)
		{
			osg::Geometry* geom = dynamic_cast(geode.getDrawable(i));
			if (!geom)
			{
				continue;
			}

			osg::Vec3Array* verts = dynamic_cast(geom->getVertexArray());
			if (!verts)
				continue;
			extracted_verts->insert(extracted_verts->end(), verts->begin(), verts->end());
		}
	}
};
int main()
{
	osg::Node* rootNode = osgDB::readNodeFile("glider.osg");
	VertexExtractor ivea;
	rootNode->accept(ivea);
	int size_t = ivea.extracted_verts.get()->size();
	std::vector::iterator iter = ivea.extracted_verts.get()->begin();
	for (int i = 0; i < size_t; i++)
	{
		std::cout << iter->x() << "" << iter->y() << "" << iter->z() << std::endl;
		iter++;
	}

	return viewer->run();
}