OSG 节点回调示例（旋转的球）

OSG 节点回调示例（旋转的球）

前言：最近开始进一步学习OSG，希望有所回报！

本文代码主要是通过节点回调，实现图元旋转！代码如下：

#include <osgViewer/Viewer>
#include <osg/NodeCallback>
#include <osg/Node>
#include <osg/Group>
#include <osg/Geode>
#include <osg/ShapeDrawable>
#include <osg/MatrixTransform>

#include <osgDB/ReadFile>
#include <osgDB/WriteFile>

#include <osgUtil/Optimizer>

osg::ref_ptr<osg::Geode> createShape()
{
	//创建一个叶节点
	osg::ref_ptr<osg::Geode> geode = new osg::Geode();

	//设置半径
	float radius = 0.8f;
	//创建精细度对象，精细度越高，细分就越多
	osg::ref_ptr<osg::TessellationHints> hints = new osg::TessellationHints();

	hints->setDetailRatio(0.5f);

	//添加一个球体
	geode->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0.0f, 0.0f, 0.0f), radius), hints.get()));

	//添加一个正方体
	geode->addDrawable(new osg::ShapeDrawable(new osg::Box(osg::Vec3(2.0f, 0.0f, 0.0f), 2*radius), hints.get()));
	return geode.get();
}

class SphereCallback : public osg::NodeCallback
{
public:
	SphereCallback():angle(0), scale(1){}

	virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)
	{
		//创建矩阵变换节点
		osg::ref_ptr<osg::MatrixTransform> mt = dynamic_cast<osg::MatrixTransform*>(node);

		//创建矩阵
		osg::Matrix mr;
		mr.makeRotate(angle, osg::Vec3(0.f, 0.f, 1.f));
		//mr.makeScale(scale, scale, scale);
		mt->setMatrix(mr);
		angle += 0.1f;
		//scale -= 0.001f;
		//if (scale == 0.0f)
			//scale = 1.0f;
		traverse(node, nv);
	}

private:
	double angle;
	double scale;
};

int main()
{
	osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();
	osg::ref_ptr<osg::Group> root = new osg::Group();
	osg::ref_ptr<osg::Geode> geode = new osg::Geode();

	geode = createShape();
	//创建矩阵变换节点
 	osg::ref_ptr<osg::MatrixTransform> mt = new osg::MatrixTransform();
	mt->addChild(geode.get());
 	mt->setUpdateCallback(new SphereCallback());
 	root->addChild(mt.get());

	//优化场景数据
	osgUtil::Optimizer optimizer;
	optimizer.optimize(root.get());

	viewer->setSceneData(root.get());
	viewer->realize();
	viewer->run();

	return 0;
}

运行截图：