FRAME RATE

T&F

Frame rate (also known as frame frequency) is the frequency (rate) at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems. Frame rate is most often expressed in frames per second (FPS), and is also expressed in progressive scan monitors as hertz (Hz).

Frame rates in video games refer to the speed at which the image is refreshed (typically in frames per second, or FPS). Many underlying processes, such as collision detection and network processing, run at different or inconsistent frequencies or in different physical components of a computer. FPS affect the experience in two ways: low FPS does not give the illusion of motion effectively and affects the user's capacity to interact with the game, while FPS that vary substantially from one second to the next depending on computational load produce uneven, “choppy” animation. Many games lock their frame rate at lower but more sustainable levels to give consistently smooth motion.

The first 3D first-person shooter game for a personal computer, 3D Monster Maze, had a frame rate of approximately 6 FPS, and was still a success. In modern action-oriented games where players must visually track animated objects and react quickly, frame rates of between 30 to 60 FPS are considered acceptable by most, though this can vary significantly from game to game. Modern action games, including popular console shooters such as Halo 3, are locked at 30 FPS maximum, while others, such as Unreal Tournament 3, can run well in excess of 100 FPS on sufficient hardware. The frame rate within games varies considerably depending upon what is currently happening at a given moment, or with the hardware configuration (especially in PC games.) When the computation of a frame consumes more time than is alloted between frames, the frame rate decreases.

A culture of competition has arisen among game enthusiasts with regard to frame rates, with players striving to obtain the highest FPS possible, due to their utility in demonstrating a system's power and efficiency. Indeed, many benchmarks (such as 3DMark) released by the marketing departments of hardware manufacturers and published in hardware reviews focus on the FPS measurement. Even though the typical LCD monitors of today are locked at 60 FPS, making extremely high frame rates impossible to see in realtime, playthroughs of game “timedemos” at hundreds or thousands of FPS for benchmarking purposes are still common.

Beyond measurement and bragging rights, such exercises do have practical bearing in some cases. A certain amount of discarded “headroom” frames are beneficial for the elimination of uneven (“choppy” or “jumpy”) output, and to prevent FPS from plummeting during the intense sequences when players need smooth feedback most.

Aside from frame rate, a separate but related factor unique to interactive applications such as gaming is latency. Excessive preprocessing can result in a noticeable delay between player commands and computer feedback, even when a full frame rate is maintained, often referred to as input lag.

Without realistic motion blurring, video games and computer animations do not look as fluid as film, even with a higher frame rate. When a fast moving object is present on two consecutive frames, a gap between the images on the two frames contributes to a noticeable separation of the object and its afterimage in the eye. Motion blurring mitigates this effect, since it tends to reduce the image gap when the two frames are strung together The effect of motion blurring is essentially superimposing multiple images of the fast-moving object on a single frame. Motion blurring makes the motion more fluid to the human eye, even as the image of the object becomes blurry on each individual frame.

A high frame rate still does not guarantee fluid movements, especially on hardware with more than one GPU. This effect is known as micro stuttering.