这是游戏循环的一个很好的实现吗 [英] Is this a good implementation of the gameloop

问题描述

我已经在 Flash/Actionscript/Starling 中实现了一个游戏循环，我想把它扔给你看看这是否是一个有效的实现.我想采用可变时间步长方法.

I have implemented a gameloop in Flash/Actionscript/Starling and I want to throw it at you to see if this is a valid implementation. I wanted to have a variable time step approach.

private var _deltaTime:Number = 0;
private var _lastTime:Number = 0;
private var _speed = 1000 / 40;

private function onEnterFrame() {
    var now = new Date().getTime();
    var delta = now - _lastTime;
    _deltaTime += delta - _speed;
    _lastTime = now;

    //skip if frame rate to fast
    if (_deltaTime <= -_speed) {
        _deltaTime += _speed;
        return;
    }
    update();
}

private function update() {
    updateGameState();

    if (_deltaTime >= _speed) {
        _deltaTime -= _speed;
        update();
    }
}

到目前为止我得到的是我有一个恒定的速度(或多或少).

What I got sofar is that I have a constant speed (more or less).

我的问题是有没有更好的方法可以让动作看起来更均匀更流畅.

My question is is there a better approach so that the movements will appear even smoother.

令我惊讶的是，即使您的 FPS 也几乎是恒定的(60FPS)与天真的游戏循环相比，移动有时会崎岖不平，但更流畅.

What is really surprising to me is that even thou the FPS is pretty much constant (60FPS) the movement is sometimes bumpy yet smoother than with the naive gameloop.

推荐答案

您走在正确的轨道上 - 假设 onEnterFrame 以某种方式由 Event.ENTER_FRAME 触发 - 而不是跳过更新，而是在每一帧上调用它，但传入时间过去了:

Youre on the right track - assuming that onEnterFrame is triggered in some way by Event.ENTER_FRAME - instead of skipping update, call it on every frame but pass in the time elapsed:

private function onEnterFrame() {
    var now = new Date().getTime();
    var delta = now - _lastTime;
    _lastTime = now;
    updateGameState(delta/1000);//divide by 1000 to give time in seconds
}

在 updateGameState 中，您可以使用 'delta' 来计算移动等，例如:

In updateGameState, you can utilise 'delta' to calculate movement etc, eg:

function updateGameState(timeElapsed:Number):void {
    myAlien.x += myAlienSpeedPerSecond*timeElapsed;
}

这样，即使帧速率发生变化，您也能获得流畅的运动.

This way you get smooth movement even when frame rate varies.

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