Adobe 38039336 - Flash CS3 Professional User Manual page 494

Animation frame rate and performance
When you add animation to an application, consider the frame rate that you set your FLA file to. Frame rate 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 faster than it does at 12 fps, so the total duration (in seconds) is shorter.
Therefore, to make a 5-second animation using a higher frame rate, you must add additional frames to fill those five
seconds than at a lower frame rate (and thus, 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.
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 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.
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. High frame rates (more than 30 to 40 fps) put a lot of stress on
processors, and do not change the appearance of the animation much or at all at runtime.
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.
Filters and SWF file performance
If you use too many filters in an application, you can use large amounts of memory and cause Flash Player perfor-
mance to suffer. Because a movie clip with filters attached has two bitmaps that are both 32-bit, these bitmaps can
cause your application to use a significant amount of memory if you use many bitmaps. The computer's operating
system might generate an out-of-memory error. On a modern computer, out-of-memory errors should be rare,
unless you are using filter effects extensively in an application (for example, you have thousands of bitmaps on the
Stage).
However, if you do encounter an out-of-memory error, the following occurs:
• The filters array is ignored.
• The movie clip is drawn using the regular vector renderer.
• No bitmaps are cached for the movie clip.
After an out-of-memory error occurs, a movie clip never attempts to use a filters array or a bitmap cache. Another
factor that affects player performance is the value that you use for the quality parameter for each filter that you apply.
Higher values require more CPU and memory for the effect to render, whereas setting the quality parameter to a
lower value requires fewer computer resources. Avoid using an excessive number of filters, and use a lower quality
setting when possible.
Important: If a 100 pixel by 100 pixel object is zoomed in once, it uses four times the memory since the content's dimen-
sions are now 200 pixels by 200 pixels. If you zoom another two times, the shape is drawn as an 800 pixel by 800 pixel
object which uses 64 times the memory as the original 100 pixel by 100 pixel object. Whenever you use filters in a SWF
file, disable the zoom menu options from the SWF file's context menu.
FLASH CS3 488
User Guide