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I started over 50 FPS on the iPhone, but now I'm bellow 30 PFS, I've seen most iPhone games clamped to either 60 or 30 FPS, even when 24 or less would give the illusion of movement.

I've concidered my limit to be a little bit over 15 FPS, in fact my physics simulation is updated at that rate (15.84 steps/s) as that is the lowest that still give fluid movement, a bit lower gives jerky motion.

Is there a practical reason why to clamp FPS way above the lower limit?

Update:

The following image could help to clarify

enter image description here

I can independently set the physic simulation step, frame rate, and simulation interval update.

My concern is why should I clamp any of those to values greater than the minimum?

For instance to conserve battery life I could just to choose the lower limits, but it seems that 60 or 30 FPS are the most used values.

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You can always interpolate between two states of the physics simulation. But really, I would suggest you to optimize your physics code in order to run it more often. –  API-Beast Dec 15 '12 at 12:31
    
Is your question Why have FPS > 24 when already 24 gives illusion of movement? –  Anko Dec 15 '12 at 14:01
    
@Anko Yes, should I care about battery life, for instance. I've updated my question to help clarify. –  rraallvv Dec 15 '12 at 14:31
    
Well, typically 24 is the bare minimum, so anything higher would look better. 30 is a typical fps for mobile. 60 is about the highest most go because of monitor refresh rates as well as the eye's perception –  CobaltHex Dec 15 '12 at 15:01

3 Answers 3

up vote 5 down vote accepted

There is no fixed "lower limit" when motion looks smooth. It's all dependent on the resolution of the display, the amount of movement, the speed of movement, and on high-DPI displays like an iPad 3/4, the resolution of the player's eyes and their distance from the screen.

If nothing in your game moves or reacts more than one pixel every second, you don't need anything more than 1fps. If something in your game moves 25 pixels a second, 25fps will look smoother than 24fps. Conversely, even at 60fps, sufficiently fast or large motion will appear jerky.

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+1, even 10fps may look smooth motion. –  Krom Stern Dec 15 '12 at 17:30
    
So I should playtest among different devices to find the lower limit regarding my particular game. I though there was a kind of common acceptance for 30 or even 60 FPS, those seem to me a waste of CPU/GPU/Battery-Life, and I was curious about the reason for that. –  rraallvv Dec 15 '12 at 19:01
    
-1 the thing with the 60fps doesn't make that much sense because a) at some point it is not anymore perceptable (you can't tell the difference between 120 fps and 300 fps because technically you can't see it)(even if you ignore the fact that your monitor can only display @60hz or @120hz) b) the visual system is far too much delayed that its possible that you can notice a difference between say 60fps/120fps –  Quonux May 22 at 14:19

A framerate which is experienced as "smooth" by the player depends greatly on the perspective of your game.

When you have a 2d game which never moves the viewpoint, 12 fps already seem smooth enough.

When you add scrolling, you need at least 24 to make the scrolling feel smooth.

A 3d first person perspective doesn't seem really smooth unless you have at least 60 fps.

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While I agree with your premise, your data appears to ignore a lot of other factors that weigh in. A fast-paced and action packed FPS will probably need a higher framerate than a slow stealth game or a darkly lit first person horror adventure. A flight simulator could get by with even less frames, despite using a similar perspective. –  Marcks Thomas Dec 16 '12 at 11:40

While 24fps is the framerate of movies and that gives the illusion of movement visually, there are a couple of caveats to consider.

First off, movie frames have motion blur in them naturally and that makes fast movements look more continuous between frames. Games generally don't have motion blur to connect fast movement between frames, so they need higher framerates in order for fast movements to look continuous.

Secondly, our sensitivity to responsiveness is greater than our sensitivity to visuals. In other words, in a fast paced twitchy game the controls will feel sluggish if there is too much of a lag between when you press a button and when the game responds. The difference between 30fps and 60fps in responsiveness isn't going to be noticed on a slower paced puzzle game, but will be noticed on something like a multiplayer first-person shooter.

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Hmm... had not thought of that. My game is kind of at "slow pace", user actions have not so much signiticative influence, because the game tries to assist the user, and tolerates a wide variation in input (think on AngryBirds). Although, if I notice some lack of responsiveness, I can optimize my game logic. –  rraallvv Dec 15 '12 at 15:22
    
Regarding both visual sentitivity and user responce, are you suggesting that users kind of interpolate what position the object sould be in between frames, and try to interac accordingly. So the game sould always "sense" at a faster rate that the FPS. It makes sense. –  rraallvv Dec 15 '12 at 15:23
    
I guess that's what I'm saying, yes. I mean it's very subconscious; I just mean that when someone flicks the mouse right in order to aim at a fast moving target, they'll miss if the game starts turning them a fraction of a second too late. –  jhocking Dec 15 '12 at 16:21

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