Game Development Reference
In-Depth Information
plex motion. In other words, by showing individual frames with specific frequency, it
ispossibletofillthemwithbreathandgivethemlife.Thespriteanimationingamesis
based on phi phenomenon as well. Game engines show separate frames in continu-
ous succession, but players perceive it like a live scene. Hence, to create an illusion
of motion on the screen, you need several main phases and the correct frequency,
which is very important because the convincing of the phi phenomenon is directly
related with the time between phases. The illusion can be totally broken if the fre-
quency is too low. For example, when the length of time between frames becomes
longer then 500 ms, it is more likely for images to be interpreted as individual pic-
tures rather than part of a single scene.
The traditional frame rate for motions pictures, which appeared with the introduction
of the sound cinema, is 24 unique frames per second (the projection frame can be
higher, 48 FPS or 72 FPS, which means that each unique frame is shown twice or
thrice). There are many debates about this value, but unquestionably, it gives the fa-
miliar "cinema experience," which looks more genuine than pictures shot on video
cameras; video cameras utilize higher frequencies. You can use 24 FPS for your an-
imation. The result will be spectacular and very smooth, and all gestures will be very
fluent. But, on the other hand, it will require more efforts on animation development
(mainly on its fine tuning) and sprite sheets files will be larger. If everything is critical
to your project, meet the requirements half way: reduce the frame to 12 FPS. For a
long time, many traditional animated masterpieces were "shooting on twos." Despite
the fact that such animation features were played at the normal cinema speed, in
reality, the unique frames were burned on film twice. So, there were only 12 unique
images per second, but they were displayed longer to fit the 24-FPS format. This
was possible because 12 frames is nearly minimum comfort frame rate to perceive
motion. Although it is not ideal, it is considered pretty satisfactory.
