Re: FLASH: Bitmap Motion Tweens not smooth enough

[Marc Hoffman, Poison Dart Frog Media]

At 09:36 AM 8/28/2000, you wrote:

>Hi everyone,

>

>I have a client who wants me to create a 20 minute flash 

>presentation.  There will need to be a constant stream of large, slow 

>moving bitmaps, motion tweening from the right side of the screen to the 

>left.  (to display their new product line) No matter what I try, the 

>pictures are just not smooth enough as they move.  I have already tried 

>different types of JPEG quality on export; checking/unchecking the "Allow 

>Smoothing" button and different frame rates with limited results.

>

>Anyone have any tips on this?

>

>Thanks a lot

>

>Diana



Diana,


The reason your bitmaps don't tween faster has to do with the number of 

pixels the playback computer must render every frame. If you use bitmaps 

that take up the whole screen, and they're constantly moving, an 800x600 

display is forced to redraw 480,000 pixels every frame. At 12 fps this 

means nearly 6 million pixel renderings per second! At 1024x768 the number 

goes up to 9.4 million renderings per second -- a whole lot of 

computations, especially for an older machine.


The solution is to move fewer pixels per frame. This can be achieved by 

reducing the dimensions of your movie. Set the movie to display at a fixed 

pixel size or at 100% (rather than full-screen), or at just a percentage of 

the screen size (for the Web, control this settting in the publisher 

settings or in the HTML code). Or you can redesign the Flash, making the 

bitmaps smaller within the movie so the playback computer doesn't have to 

redraw the entire stage area, just the areas that are moving. Look at 

http://www.hillmancurtis.com to see how beautifully Flash can animate 

bitmaps when their size is constrained. I realize your client might be 

married to the idea of larger bitmaps, but do consider that smaller can be 

more effective, especially if used to draw the eye where it needs to go.


Director is better at rendering bitmap movement than is Flash, but produces 

larger file sizes. It might be a better choice for your project, especially 

if for local (non-Web) delivery.


By the way, if this is for Web playback, I hope you're giving thought to 

how much content must be streamed to keep up with a constant delivery of 

large bitmaps. 28.8Kbps modems can download about 2.3k of content per 

second. If your movie uses content at a faster rate than that, you'll need 

to build in preloaders or the movie will simply stall from time to time 

while the next required image loads. This will be a problem only the first 

time it loads; thereafter the movie will play from the browser cache.


Hope this is helpful. I have a bit more discussion at 

http://www.dartfrogmedia.com/wsa.




Marc Hoffman


Poison Dart Frog Media: Web Animation and Multimedia Design

Flash portfolio: http://www.dartfrogmedia.com/portfolio



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