FPS

FPS stands for frames per second, or on average, how many different frames of animation are displayed in a game over the course of one second. This number can vary wildly depending on the complexity of a game (at any given moment) and the hardware used to run it; in fact, a fractional FPS number would result in frames that actually take more than one second to display, akin to a slideshow.

Many people say that having high FPS in games is not necessary, citing the fact that films are typically recorded at 24 FPS and American television runs at 30 FPS (or technically, 29.97 FPS). What these people fail to realize, is that cameras record more than one perfect "instant" on film; depending on their shutter speed, they actually record an entire interval of time which captures any motion which occurred within it--which is why even the best films on DVD are blurred to some degree when paused, as the entire range of motion was compressed into that image. In a film, every second of actual time is represented and accounted for in the recording. However, in a computer game, each screen you see is indeed only an "instant" and each must be constructed and displayed individually.

How many FPS required for a game to appear smoothly varies wildly depending on the genre. For an extreme example, a game of checkers would barely require any, the screen only needing to be changed upon the completion of a move. On the other hand, most flight simulators and racing games need at least 24-30 FPS to give the illusion of reality, though need more to be especially convincing.

However, 60 FPS is largely agreed upon for being a desirable number across the board to guarantee smooth play. Remember, we are talking about the average FPS here. Not every second of game play is the same, as some scenes or levels are more stressful on the computer than others meaning that the number of frames it is rendering is always going up and down. A higher average FPS usually means that the minimum FPS level is also higher, making a game less likely to "bog down" or get choppy during particularly frantic moments.

In fact, for first-person shooter games (which coincidentally, and confusingly, are also commonly abbreviated "FPS"), having a high FPS is even more important--especially if a player is involved in online gaming against others on the internet.

To illustrate this: a player in a game might quickly turn all the way around to survey the virtual landscape. This would be a rotation of 360 degrees in one second. That means, at 30 FPS, that each time the screen was updated the player had already turned 12 degrees. At 60 FPS, the player would get an update every six degrees--and at 120 FPS, the player's target reticule would track a mere three degrees between updates. This allows for much more precise movement and tracking of opponents as play moves very quickly. Very competitive online gamers often turn down the detail settings of their games to achieve extremely high frame rates for this reason.

However, there is another factor besides the speed of your computer and video card: your monitor. Monitors only update a certain number of times a second as well, and this frequency is measured in Hz. This becomes more confusing, because depending on the resolution, monitors are capable of refreshing at different speeds. For example, a monitor might be able to refresh 120 times per second, or 120 Hz, at the resolution of 640x480 pixels, but 75 Hz at 1024x768, and yet only 60 Hz at 1600x1200. So while your monitor might be capable of gaming at high resolution, it might not be as capable as you think.

60 Hz should be considered a bare minimum because it causes fatigue and eyestrain in nearly all people. 70-75 Hz should be an acceptable minimum for most users, while for some, 85 Hz is much more comfortable. Anything beyond that is just gravy--at 160 Hz, for example, a digital photograph of your monitor would likely not reveal a scan-line or half drawn image. Pushing the status button on most modern monitors will display the refresh information, at any given moment.

The refresh rate of the monitor is also connected to FPS in games because the game can only draw a new frame as the monitor also begins to draw a new frame. If your monitor is only running at 60 Hz, it would then be impossible for it to display over 60 FPS, even if your computer were generating them. In fact, you would often be seeing far less than 60 FPS as the computer can only draw a new frame when the monitor is also beginning to draw a new frame. If another frame is ready to be drawn and the monitor is still in the process of drawing the last, this new frame is lost, and so would any others that were created during the interval of drawing that frame. This can sometimes result in a significant number of dropped frames.

This picture simulates the effect of "tearing"
which is produced when v-sync is turned off
with a low monitor refresh rate.

To get around this limitation, gamers often disable a feature called "v-sync" or "vertical sync" in their video drivers (the function is usually buried several layers deep in their computer's display properties). By turning v-sync off, the monitor is then effectively fed partial frames, as it begins drawing the latest frame available without waiting for a new cycle to "sync." But as only partial frames are drawn, this can sometimes result in "tearing" (this is more noticeable in games that use DirectX rather than those which use OpenGl, as the latter actually does not contain a v-sync function and handles the feature differently) where "seams" appear when there is fast motion in games--though this is encountered far less with modern video cards than it was in the past as it is more evident in displays with lower refresh rates (60-72 HZ.)..