ogre 3d 1.7 beginner’s guide 第四章 第三小节 中文翻译 帧监听

FrameListener

【 帧监听 】

The new concept we have encountered here is the concept of FrameListeners. As the name suggests, a FrameListener is based on the observer pattern. We can add a class instance which inherits from the Ogre::FrameListener interface to our Ogre 3D root instance using the addFrameListener() method of Ogre::Root. When this class instance is added, our class gets notified when certain events happen. In this example, we overrode the frameStarted() method.

【 我们在此遇到的一个新概念就是帧监听。顾名思义，帧监听是基于一个观察者的模式。我们可以添加一个类的实例。你可以使用Ogre::Root的addFrameListener()方法，通过继承自Ogre::FrameListener的接口，添加一个对象到我们的Ogre3D根对象中。当对象被添加时，在确定的事件发生时我们的类就会得到通知。在这个例子中，我们重写了frameStarted()方法。】

Before a frame (by frame, we mean a single picture of the scene) is rendered, Ogre::Root iterates over all added FrameListeners and calls the frameStarted() method of each one. In our implementation (see step 4) of this function, we translated the node 0.1 units on the x-axis. This node was passed to the Framelistener in its constructor. Therefore, each time the scene is rendered, the node is translated a bit, and as a result, the model moves. As we have seen during the running of the application, we can't move our camera or exit our application using the Escape key. This is because these things were done by the FrameListener, which comes with the ExampleApplication framework. The ExampleApplication framework comes with the SDK. Now that we have replaced it with our own implementation, we can't use the functions the FrameListener offers any longer.

But we will reimplement most of them in this chapter, so no worries. If needed, we could still

call the functions of the base class to get our default behavior back.In step 4, our function returns true. If it returned false, Ogre 3D would interpret this as a signal to drop out of the render loop, and with this, the application would be closed. We will use this fact to reimplement the "press Escape to exit the application" function.

【 在帧（帧，意思是指场景中的单个图像）被渲染之前，Ogre::Root 遍历所有添加的Framelistener并调用每个的frameStarted()方法。我们第四步中的函数定义中，我们沿X轴每帧0.1单位的速率变换结点。这个结点通过Example25FrameListener构造函数的返回地址传递给Framelistener。因此，场景每次被渲染的时候，结点就变换一点位置。结果，模型就移动了。正如我们在程序运行时看到的，我们不能移动摄像机或使用Escape 键退出。这是因为这些是由Framelistener来操作的，而这个FrameListener是ExampleApplication 框架自带的。ExampleApplication是SDK自带的。现在我们代替其原有的FrameListener，使用我们自己定义的实现过程。这样我们就不能使用自带的Framelistener，但是这章我们将会重新实现他们中的大部分，所以不用担心。如果需要，我们可能仍然调用基类的成员函数来获得默认的行为。在第四步中，我们函数返回true。如果返回false，Ogre 3D 将会解释false为退出渲染循环的标志，而与此同时，程序就会结束。我们将会使用重新实现“按Escape键退出”的函数。】

Pop quiz – design pattern of FrameListener

【 简单测试 —— FrameListener的设计模式 】

1.  On which design pattern is the FrameListener concept based?

【 1. Framelistener概念的模式是基于?】

a.  Decorator 【装饰者】

b.  Bridge     【桥】

c.  Observer 【观察者】