Tag Archives: performance

Fastest way to add multiple elements to an Array / Vector in AS3

In a simple situation, where you wish to add many elements to an Array or Vector, you might just do:

However, the sizes of both Arrays are manipulated for each loop, which will have an adverse impact on speed and memory usage. So, we could cache the length of the input Array and not manipulate it:

But we’re still growing the size of the output Array incrementally, which is very bad. Since we know input.length in advance, we could grow the output Array to its new size just once, before the loop:

This is OK, but still involves a loop. If only we could push multiple elements into the push method in one go. Well, we can – enter the apply method. Since Array.push accepts multiple arguments (something rarely used) and apply allows us to pass an Array of arguments to any Function, one line and we’re done:

This works out faster and more memory efficient than the other methods. It works nicely for Vectors, too. If anyone has a faster method of doing this, do let me know.

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SWFIdle – simple flash idling utility

If you’re still churning out Flash banners, please use this!

swfidleI created this simple utility, called SWFIdle, to enable the Flash Player to lower its CPU usage while the user is not interacting with it. Since it’s possible to have multiple Flash instances embedded in one page (for example, a game and a couple of banners), I recommend using this in your projects, so that Flash instances needn’t fight for CPU and give Flash a worse name than it has already 😉


I know there’s the hasPriority embed attribute now. But:

  • That assumes you have access to the HTML that embeds your SWF
  • If no other players are present, it has no effect
  • There’s still usually little reason to be running your SWF at a high framerate if the user isn’t interacting with it
  • Flash banners with wastefully unoptimised drawing routines are probably one of the key reasons that Flash got poo-pooed off of mobile platforms and disabled on everyone’s laptops – CPU usage = battery usage!

Synchronising animation across multiple player instances

I’ve been asked a few times how to create effects that require multiple instances of the Flash Player on a page to remain ‘in sync’, even with user interaction. Reading and writing to cookies frequently is inefficient and resource heavy. Also, when you have more than 2 SWFs, deciding which SWF updates who becomes tricky – especially if someone decides to change or remove an instance, or an instance which you picked as ‘master’ is not loaded, for some reason.

So, I came up with this solution, using LocalConnection with a twist, which works pretty well. But, if anyone has a better method, drop it in a comment below 🙂

ActionScript performance tips

Here are a few simple tricks that may help the performance of your code/graphics intensive Flash movies. This is not an exhaustive list, by any means, rather some of the more effective performance tweaks to try out on your projects. There are the usual sensible coding tricks, like using local variables for oft-used references within functions, or planning your code loops carefully and breaking out of loops whenever feasible – but you should be doing these already. I’ll be adding to this post as and when I feel necessary, but will generally avoid the more granular tricks, such as bytecode optimisation. Some of those methods are too complex to explain in simple terms here and generally have a low effort-to-benefit ratio anyway:

Use scrollRect in conjunction with cacheAsBitmap. The cacheAsBitmap parameter of a movieclip can improve performance dramatically, but will cause problems if the render area of the movieclip gets too large (e.g. larger than 2880 in width or height), regardless of whether it is cropped by the viewable area of the Flash Player. The solution is to use scrollRect to constrain the rendering area to desired limits, in this example, the stage width/height:

Create bitmap snapshots of complex movieclips. Where you may have a movieclip full of layered graphical effects that isn’t animated, you can save a lot of rendering time by creating a snapshot of the movie. Similar to the cacheAsBitmap parameter, but will improve performance further if your movieclip comprises many lines or alphas. The following function shows a quick and dirty way of duplicating a movieclip as a snapshot of the original:

Use the opaque window mode trick – sparingly! Setting the wmode=opaque HTML parameter of your Flash object can improve rendering performance, but at a potential cost. Not only does it make the rendering order of movieclips and frames more ‘lazy’, but will effect keyboard interaction adversely in some browsers (especially FireFox). Use with caution.

I’ll be updating and tracking back to this post occasionally, so stay tuned…