当帧速率受到限制时，对象移动不稳定
我在游戏中遇到了一些物体移动不稳定的问题。
如果帧速率不受限制，游戏运行会很流畅。
如果我将帧速率限制为 60 fps，则运动会变得不稳定。
对象的运动看起来像这样...
m_distance += m_speed * GetFrameTime()
其中速度以每秒像素为单位，GetFrameTime() 返回自上一帧以来经过的时间。请注意，对象仅沿 x 和 y 方向移动。
我正在使用 SFML，其中包含函数 SetFramerateLimit(60) 和 UseVerticalSync(true)。在尝试解决不稳定的运动问题时，我阅读了 XNA 开发人员的一篇文章，介绍了它们如何更新一次、渲染一次，以及游戏循环中是否还有剩余时间。帧速率（即 1/60），然后他们将在该时间段的剩余时间内睡眠。我相信这就是 SFML 所做的，因为我禁用了这些功能并写入了该行为，并且我得到了相同的症状。
我并不是说上述方法是一件坏事。事实上，我喜欢应用程序没有做不必要的工作（在设置帧限制和没有设置帧限制的情况下运行应用程序时，资源使用情况存在明显差异）。不过，我实在不知道为什么动作会断断续续。我读过 gafferongames 的文章，但它们似乎不适用于这里。
如有任何帮助，我们将不胜感激，谢谢。
编辑：我已经确定了问题，现在只是不知道如何解决。
在对象“跳跃”的帧上，m_distance 明显大于其他帧中的距离。仔细观察，GetFrameTime() 也明显大于之前帧之间的时间（显着差异约为 2-3 毫秒）。
Edit2：我相信我已经想出了一个解决方案，感谢 http://gafferongames。 com/game-physicals/fix-your-timestep/ 。设置固定的增量时间而不是使用 GetFrameTime。
I've been having some trouble with choppy movement of objects in a game.
If the frame rate isn't capped, the game runs smooth.
If I cap the frame rate at say, 60 fps, the movement is choppy.
An object's movement looks like this...
m_distance += m_speed * GetFrameTime()
Where speed is in pixels per second, and GetFrameTime() returns the time elapsed since the last frame. Note that objects only move in x and y directions.
I'm using SFML, with the functions SetFramerateLimit(60) and UseVerticalSync(true). While trying to address the choppy movement issue, I read an article from an XNA developer about how they update once, render once, and then if there is time left in the game loop < the frame rate (i.e. 1/60) then they'll sleep for the rest of that period. I believe this is what SFML does, because I disabled those functions and wrote in that behavior and I got the same symptoms.
Now I'm not saying the above approach is a bad thing. In fact, I like that the application isn't doing needless work (there is a noticeable difference in resource usage when running the application with a set frame limit and without one). However, I really don't know why the movement is choppy. I've read the gafferongames articles but they don't seem to apply here.
Any assistance is appreciated, thanks.
Edit: I've identified the the issue, now just not sure how to solve it.
On the frames where the object "jumps", the m_distance is significantly greater than distances in other frames. On closer inspection, the GetFrameTime() is also significantly greater than previous times between frames (significant is like 2-3 ms difference).
Edit2: I believe I've come up with a solution thanks to http://gafferongames.com/game-physics/fix-your-timestep/ . Set a fixed delta time instead of using GetFrameTime.
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使用的唯一原因
是：如果您想获得与帧无关的运动。在这种情况下，没有理由限制 FPS。
当您有 FPS 上限（例如 SFML 实现的）时，我建议保持每帧的运动恒定。也就是说，像这样：
The only reason to ever use:
is if you're trying to get frame-independent movement. In this case, there's no reason to cap your FPS.
When you have a FPS cap such as what SFML implements, I recommend keeping movement constant per frame. That is to say, something like this: