MACROMEDIA FLASH 8-LEARNING ACTIONSCRIPT 2.0 IN FLASH - Page 471

Scripting animation with ActionScript 2.0 471
About animation and frame rate
When you add animation to an application, consider the frame rate that you set your FLA file
to. You need to think about frame rate when working with animations because it can affect
the performance of your SWF file and the computer that plays it. Setting a frame rate too
high can lead to processor problems, especially when you use many assets or use ActionScript
to create animation.
However, you also need to consider the frame rate setting, because it affects how smoothly
your animation plays. For example, an animation set to 12 frames per second (fps) in the
Property inspector plays 12 frames each second. If the document’s frame rate is set to 24 fps,
the animation appears to animate more smoothly than if it ran at 12 fps. However, your
animation at 24 fps also plays much faster than it does at 12 fps, so the total duration (in
seconds) is shorter. Therefore, if you need to make a 5-second animation using a higher frame
rate, it means you need to add additional frames to fill those five seconds than at a lower frame
rate (and thus, this raises the total file size of your animation). A 5-second animation at 24 fps
typically has a higher file size than a 5-second animation at 12 fps.
Use the lowest possible frame rate that makes your animation appear to play smoothly at
runtime, which helps reduce the strain on the end-user’s processor. Try not to use a frame rate
that’s more than 30 to 40 fps; high frame rates put a lot of stress on processors, and do not
change the appearance of the animation much or at all at runtime.
Also, especially if you’re working with timeline-based animation, select a frame rate for your
animation as early as possible in the development process. When you test the SWF file, check
the duration, and the SWF file size, of your animation. The frame rate greatly affects the
speed of the animation.
NOTE
When you use an onEnterFrame event handler to create scripted animations, the
animation runs at the document’s frame rate, similar to if you created a motion tween on
a timeline. An alternative to the
onEnterFrame event handler is setInterval (see
setInterval function in the ActionScript 2.0 Language Reference). Instead of
depending on frame rate, you call functions at a specified interval. Like
onEnterFrame, the
more frequently you use
setInterval to call a function, the more resource intensive the
animation is on your processor.