所以读者大概。就行明确博主为什么要在类内部定义的当前时间了。我们通过这个所谓的当前时间来与系统实际的当前时间进行比較，计算出时间间隔，从而控制节点进行移动。

        想要实现自己的Animator是不是十分的简单啊？？？仅仅要掌握了这个主要的规则。我们就能够发挥我们自己的想象来制作出十分复杂的Animator出来。

大家能够借鉴下cocos2d-x里面的Action,试着在Irrlicht中也实现它们，而且将代码共享出来给大家使用。假设有空的话，博主可能会自己实现一些Animator共享给大家使用。

       完整的代码和教程4中的代码一致。所不同的是将FlyCircleAnimator换成我们这里自定义的Animator而已，例如以下所看到的：

#include<irrlicht.h>
#include"MyEventReceiver.h"
#include"CMyRollAnimator.h"
using namespace irr;
using namespace core;
using namespace gui;
using namespace scene;
using namespace video;

#ifdef _IRR_WINDOWS_
#pragma comment(lib,"irrlicht.lib")
#pragma comment(linker,"/subsystem:windows /ENTRY:mainCRTStartup")
#endif

int main()
{
	//Create the irrdevice
	MyEventReceiver _receiver;
	IrrlichtDevice* _pDevice = createDevice(EDT_DIRECT3D9,dimension2d<u32>(800,640),32U,
		false,
		false,
		false,
		&_receiver);

	//Check if create successfully
	if(NULL == _pDevice)
		return 1 ;

	//Get the video driver and scene manager
	IVideoDriver* _pVideoDriver = _pDevice->getVideoDriver();
	ISceneManager* _pSceneManager = _pDevice->getSceneManager();

	//Create a sphere node
	ISceneNode* _pNode = _pSceneManager->addSphereSceneNode();

	//Check if create successfully
	if(NULL == _pNode)
		return 1 ;
	_pNode->setPosition(vector3df(0,0,30));
	_pNode->setMaterialTexture(0,_pVideoDriver->getTexture("wall.bmp"));
	_pNode->setMaterialFlag(EMF_LIGHTING,false);

	//Create a cube node
	ISceneNode* _pCubeNode = _pSceneManager->addCubeSceneNode();

	//Check if create successfully
	if(NULL == _pCubeNode)
		return 1 ;
	_pCubeNode->setMaterialTexture(0,_pVideoDriver->getTexture("t351sml.jpg"));
	_pCubeNode->setMaterialFlag(EMF_LIGHTING, false);

	//Create a scene node animator for cube node
	//ISceneNodeAnimator* _pAnimator = _pSceneManager->createFlyCircleAnimator(vector3df(0,0,30),
	//	20.0f);
	CMyRollAnimator * _pAnimator = new CMyRollAnimator(vector3df(-20,0,30), vector3df(20,0,30),
		10.0f);

	//Check if create successfully
	if(NULL == _pAnimator)
		return 1 ;

	_pCubeNode->addAnimator(_pAnimator);
	
	//Drop the animator
	_pAnimator->drop();

	//Add one camera node
	_pSceneManager->addCameraSceneNode();

	int _nlastFPS = -1 ;

	u32 _uLastTime = _pDevice->getTimer()->getTime();

	const f32 MOVEMENT_SPEED = 5.0f ;

	//Do loop
	while(_pDevice->run())
	{
		const u32 _now = _pDevice->getTimer()->getTime();
		const f32 _frameDeltaTime = (f32)(_now - _uLastTime)/1000.0f;
		_uLastTime = _now ;

		vector3df _pos = _pNode->getPosition();

		if(_receiver.IsKeyDown(KEY_KEY_W))
			_pos.Y += MOVEMENT_SPEED * _frameDeltaTime ;
		else if(_receiver.IsKeyDown(KEY_KEY_S))
			_pos.Y -= MOVEMENT_SPEED * _frameDeltaTime ;

		if(_receiver.IsKeyDown(KEY_KEY_A))
			_pos.X -= MOVEMENT_SPEED * _frameDeltaTime ;
		else if(_receiver.IsKeyDown(KEY_KEY_D))
			_pos.X += MOVEMENT_SPEED * _frameDeltaTime ;

		_pNode->setPosition(_pos);

		//Draw the scene
		_pVideoDriver->beginScene();
		_pSceneManager->drawAll();
		_pVideoDriver->endScene();
	}// end while

	_pDevice->drop();

	return 0 ;
}// end 

Referenced Counter

             博主在编写这个实验程序的时候。发现当我们调用_pAnimator->drop的时候，animator并没有销毁。所以，博主对于引擎内部是怎样保存一个对象技术感到好奇。决心研究一下。

           在Irrlicht引擎中，通过一个十分简单的引用技术（Referenced Counter）系统来对系统中的对象进行跟踪。

这个功能是通过一个名为IReferenceCounted接口来实现的，引擎中大部分的类都继承了这个接口。从而实现了引用技术操作。以下来看下。这个类的申明：

// Copyright (C) 2002-2012 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h

#ifndef __I_IREFERENCE_COUNTED_H_INCLUDED__
#define __I_IREFERENCE_COUNTED_H_INCLUDED__

#include "irrTypes.h"

namespace irr
{

	//! Base class of most objects of the Irrlicht Engine.
	/** This class provides reference counting through the methods grab() and drop().
	It also is able to store a debug string for every instance of an object.
	Most objects of the Irrlicht
	Engine are derived from IReferenceCounted, and so they are reference counted.

	When you create an object in the Irrlicht engine, calling a method
	which starts with 'create', an object is created, and you get a pointer
	to the new object. If you no longer need the object, you have
	to call drop(). This will destroy the object, if grab() was not called
	in another part of you program, because this part still needs the object.
	Note, that you only need to call drop() to the object, if you created it,
	and the method had a 'create' in it.

	A simple example:

	If you want to create a texture, you may want to call an imaginable method
	IDriver::createTexture. You call
	ITexture* texture = driver->createTexture(dimension2d<u32>(128, 128));
	If you no longer need the texture, call texture->drop().

	If you want to load a texture, you may want to call imaginable method
	IDriver::loadTexture. You do this like
	ITexture* texture = driver->loadTexture("example.jpg");
	You will not have to drop the pointer to the loaded texture, because
	the name of the method does not start with 'create'. The texture
	is stored somewhere by the driver.
	*/
	class IReferenceCounted
	{
	public:

		//! Constructor.
		IReferenceCounted()
			: DebugName(0), ReferenceCounter(1)
		{
		}

		//! Destructor.
		virtual ~IReferenceCounted()
		{
		}

		//! Grabs the object. Increments the reference counter by one.
		/** Someone who calls grab() to an object, should later also
		call drop() to it. If an object never gets as much drop() as
		grab() calls, it will never be destroyed. The
		IReferenceCounted class provides a basic reference counting
		mechanism with its methods grab() and drop(). Most objects of
		the Irrlicht Engine are derived from IReferenceCounted, and so
		they are reference counted.

		When you create an object in the Irrlicht engine, calling a
		method which starts with 'create', an object is created, and
		you get a pointer to the new object. If you no longer need the
		object, you have to call drop(). This will destroy the object,
		if grab() was not called in another part of you program,
		because this part still needs the object. Note, that you only
		need to call drop() to the object, if you created it, and the
		method had a 'create' in it.

		A simple example:

		If you want to create a texture, you may want to call an
		imaginable method IDriver::createTexture. You call
		ITexture* texture = driver->createTexture(dimension2d<u32>(128, 128));
		If you no longer need the texture, call texture->drop().
		If you want to load a texture, you may want to call imaginable
		method IDriver::loadTexture. You do this like
		ITexture* texture = driver->loadTexture("example.jpg");
		You will not have to drop the pointer to the loaded texture,
		because the name of the method does not start with 'create'.
		The texture is stored somewhere by the driver. */
		void grab() const { ++ReferenceCounter; }

		//! Drops the object. Decrements the reference counter by one.
		/** The IReferenceCounted class provides a basic reference
		counting mechanism with its methods grab() and drop(). Most
		objects of the Irrlicht Engine are derived from
		IReferenceCounted, and so they are reference counted.

		When you create an object in the Irrlicht engine, calling a
		method which starts with 'create', an object is created, and
		you get a pointer to the new object. If you no longer need the
		object, you have to call drop(). This will destroy the object,
		if grab() was not called in another part of you program,
		because this part still needs the object. Note, that you only
		need to call drop() to the object, if you created it, and the
		method had a 'create' in it.

		A simple example:

		If you want to create a texture, you may want to call an
		imaginable method IDriver::createTexture. You call
		ITexture* texture = driver->createTexture(dimension2d<u32>(128, 128));
		If you no longer need the texture, call texture->drop().
		If you want to load a texture, you may want to call imaginable
		method IDriver::loadTexture. You do this like
		ITexture* texture = driver->loadTexture("example.jpg");
		You will not have to drop the pointer to the loaded texture,
		because the name of the method does not start with 'create'.
		The texture is stored somewhere by the driver.
		\return True, if the object was deleted. */
		bool drop() const
		{
			// someone is doing bad reference counting.
			_IRR_DEBUG_BREAK_IF(ReferenceCounter <= 0)

			--ReferenceCounter;
			if (!ReferenceCounter)
			{
				delete this;
				return true;
			}

			return false;
		}

		//! Get the reference count.
		/** \return Current value of the reference counter. */
		s32 getReferenceCount() const
		{
			return ReferenceCounter;
		}

		//! Returns the debug name of the object.
		/** The Debugname may only be set and changed by the object
		itself. This method should only be used in Debug mode.
		\return Returns a string, previously set by setDebugName(); */
		const c8* getDebugName() const
		{
			return DebugName;
		}

	protected:

		//! Sets the debug name of the object.
		/** The Debugname may only be set and changed by the object
		itself. This method should only be used in Debug mode.
		\param newName: New debug name to set. */
		void setDebugName(const c8* newName)
		{
			DebugName = newName;
		}

	private:

		//! The debug name.
		const c8* DebugName;

		//! The reference counter. Mutable to do reference counting on const objects.
		mutable s32 ReferenceCounter;
	};

} // end namespace irr

#endif

CIrrDeviceStub::~CIrrDeviceStub()
{
	VideoModeList->drop();
	FileSystem->drop();

	if (GUIEnvironment)
		GUIEnvironment->drop();

	if (VideoDriver)
		VideoDriver->drop();

	if (SceneManager)
		SceneManager->drop();

	if (InputReceivingSceneManager)
		InputReceivingSceneManager->drop();

	if (CursorControl)
		CursorControl->drop();

	if (Operator)
		Operator->drop();

	if (Randomizer)
		Randomizer->drop();

	CursorControl = 0;

	if (Timer)
		Timer->drop();

	if (Logger->drop())
		os::Printer::Logger = 0;
}

//! destructor
CSceneManager::~CSceneManager()
{
	clearDeletionList();

	//! force to remove hardwareTextures from the driver
	//! because Scenes may hold internally data bounded to sceneNodes
	//! which may be destroyed twice
	if (Driver)
		Driver->removeAllHardwareBuffers();

	if (FileSystem)
		FileSystem->drop();

	if (CursorControl)
		CursorControl->drop();

	if (CollisionManager)
		CollisionManager->drop();

	if (GeometryCreator)
		GeometryCreator->drop();

	if (GUIEnvironment)
		GUIEnvironment->drop();

	u32 i;
	for (i=0; i<MeshLoaderList.size(); ++i)
		MeshLoaderList[i]->drop();

	for (i=0; i<SceneLoaderList.size(); ++i)
		SceneLoaderList[i]->drop();

	if (ActiveCamera)
		ActiveCamera->drop();
	ActiveCamera = 0;

	if (MeshCache)
		MeshCache->drop();

	for (i=0; i<SceneNodeFactoryList.size(); ++i)
		SceneNodeFactoryList[i]->drop();

	for (i=0; i<SceneNodeAnimatorFactoryList.size(); ++i)
		SceneNodeAnimatorFactoryList[i]->drop();

	if (LightManager)
		LightManager->drop();

	// remove all nodes and animators before dropping the driver
	// as render targets may be destroyed twice

	removeAll();
	removeAnimators();

	if (Driver)
		Driver->drop();
}

		//! Removes all animators from this scene node.
		/** The animators might also be deleted if no other grab exists
		for them. */
		virtual void removeAnimators()
		{
			ISceneNodeAnimatorList::Iterator it = Animators.begin();
			for (; it != Animators.end(); ++it)
				(*it)->drop();

			Animators.clear();
		}