by Grant Skinner

The Case of the Disappearing Number

On a current project we were experiencing an issue with a specific numeric ID not working correctly. After some exhaustive debugging, it was isolated it to a seemingly bizarre phenomenon that manifests in both AS3 and Javascript: a missing number.

Specifically, we found that the number 10100401822940525 appears to simply not exist in these programming environment. You can test this for yourself, simply trace or log the following statements:
10100401822940524
10100401822940525
10100401822940524+1
Number(“10100401822940525”)
(10100401822940525).toString()

All of the above statements will output “10100401822940524”, when obviously all but the first one should return “10100401822940525”.

Theres no obvious significance to that value. The binary/hex value isn’t flipping any high level bit, and there are no results for it on google or Wolfram Alpha. Additional testing showed the same result with other numbers in this range.

I thought it might be related to the value being larger than the max 32bit uint value, but adding a decimal (forcing it to use a floating point Number) does not help, it simply rounds it up to “10100401822940526” instead. Number should support much higher values (up to ~1.8e308). I confirmed this with:
Number.MAX_VALUE > 10100401822940526 // outputs true

As it turns out, the issue is a side effect of how Numbers are stored. Only 53bits out of the 64bits in a Number are used to store an accurate value. The remainder are used to represent the magnitude of the value. You can read about this here. So, the maximum accurate value we can store is:
Math.pow(2,53) =
9007199254740992 < 10100401822940525 This means that the precise value is not stored. Knowing this, we can rework our logic to store the value in two uints / Numbers. Thanks to everyone on Twitter that provided input to this article. I'd name contributors individually, but I had a lot of duplicate responses, and don't want to leave anyone out.

by Grant Skinner

TweenJS: Animate, Tween & Sequence in Javascript

There were a lot of requests for tweening support in EaselJS, so to address this I thought I’d try writing a companion tweening library. I started in on this a couple days ago, and just posted the very early results to a new GitHub repo.

This is very much pre-alpha, untested, undocumented, and subject to change, but I thought I’d share it and solicit feedback.

It has a simple but powerful API that uses chained method calls to create complex tweens (similar to Graphics in EaselJS). For example, the following code will create a new tween instance that tweens the target’s x value to 300 for 400ms, waits 500 ms, then tweens the target’s alpha to 0 over 1s, sets its visible to false, and calls the onComplete function.

var myTween = Tween.get(myTarget).to({x:300},400).wait(500).to({alpha:0},1000).set({visible:false}).call(onComplete);

You can also use it to sequence commands, without tweening at all:

var mySeq = Tween.get(target).call(doStuff,[param]).wait(500).set({prop:value}).set({prop:value},foo).call(allDone);

Let me know what you think. We’re still considering whether it should live completely on its own, or be a part of EaselJS. Right now it has no dependencies on EaselJS, but it will use the same Ticker class if available. It should work to tween / sequence just about anything in Javascript, but so far I’ve only tested it with EaselJS and HTML5 canvas.

You can check out an example of TweenJS in action here. Have a look at the source code to get a better sense of how things work.

You can grab the library from the TweenJS GitHub Repo.

by Grant Skinner

Music Visualizer in HTML5 / JS with Source Code

It’s no secret that I like building music visualizers, or that I’ve been playing with HTML5 a fair amount lately. Given that, I thought I’d combine the two interests, and build a music visualizer using JS, the canvas & audio elements in HTML5, and the EaselJS framework.

The primary challenge was that Javascript doesn’t have any built in mechanism for accessing the volume of a playing audio tag. To address this I wrote a little AIR application that will read an MP3 file using Sound.extract() and export peak volume data as a text or JPG image file. I then wrote a JS class called VolumeData.js that reads in these files and provides access to the data via a simple interface (ex. myVolumeData.getVolume(time) ).

With those pieces in place and tested, I started putting together a demo of it in action using EaselJS. Two of the newest features were compositeOperation support (which let me approximate an “add” blend mode), and the drawPolyStar method, both of which I used to excess.

I think the end result is pretty cool, though it requires a fairly modern system, and will still melt your CPU – I was intentionally pushing things hard to try to find the performance limit. It requires an up to date browser to run.

I built two variations: Star Field and Atomic. Occasionally dynamic audio loading seems to break on certain browsers, just reload if it gets stuck on “loading music”.

If you’re interested in building your own music visualizers in HTML5/ Javascript, you can download the demo source, VolumeData.js class (MIT licensed) and VolumeData AIR application here. Also, be sure to check out the latest version of EaselJS (we just released v0.3.2 today).

Please let me know if you build anything cool with the code. I’d love to see it.

by Grant Skinner

EaselJS v0.3.2 Released

I’m happy to announce the release of EaselJS v0.3.2. It provides a few new interaction features, cleans up the docs, and fixes some known issues. Here’s the full list:

– added stage.mouseInBounds
– added DisplayObject.onMouseOver and onMouseOut callbacks
– added stage.enableMouseOver(freq)
– improved support for calculating mouseX/Y in divs with relative positioning
– fixed Graphics.clone()
– fixed an issue with shadows not being reset properly
– migrated to use YUIDocs instead of JSDocs
– fixed an issue that prevented BitmapSequence instances with frameData from working with gotoAndPlay(frameNumber)

I’d like to thank everyone who contributed by providing bug reports, feedback, and edits. In particular I would like to thank Mike Chambers (of Adobe fame) for all his fantastic help on EaselJS. He has been an invaluable resource for bouncing ideas off, providing a critical second perspective, and helping with code / doc edits.

As always, you can get more info and grab the latest zip from easeljs.com, or check it out on the EaselJS GitHub repository.

We’re currently finalizing plans for v0.4 (which looks to be a very aggressive undertaking), and would love any feedback or ideas you can provide here or on GitHub.

by Grant Skinner

Zoë: Export SWF Animation as EaselJS SpriteSheets

Alongside the release of EaselJS v0.3 we’re also releasing the first version of Zoë, a free Adobe AIR application for exporting SWF animations as sprite sheets (single images containing a grid of animation cells), including frame data for use with EaselJS.

This means you can use Flash Pro to lay out your animations then very easily prep them for use with EaselJS and the HTML5 canvas element.

We used an early version of Zoë to prep all of the animations for the Pirates Love Daisies game we released a few weeks ago, which let our illustration team work with a tool they felt comfortable with, using tweens, skeleton constraints, and graphic symbols.

Here’s a quick feature overview:

  • Exports a single sprite sheet image, or individual frames
  • Reads frame labels in the swf to generate frame data.
  • Writes frame data as JSON or EaselJS files
  • Calculates the frame dimensions automatically based on the animation content
  • Saves profiles to make it easy to re-export when art changes

And a screenshot:

You can grab Zoë from easeljs.com/zoe.html. It’s currently not open source, but we’ll likely release the source once we have a chance to fix any major issues that arise with the public release and clean up the code.

by Grant Skinner

EaselJS v0.3 Released!

I’m very happy to announce that version 0.3 of EaselJS has been released. Even better, it’s now on GitHub, so you can fork it to your hearts content.

This version makes it even easier to build compelling content using the HTML5 canvas element and javascript. It has a rewritten rendering engine with support for skewing, an improved and optimized interaction model (5-10x faster), and a slew of other new features and fixes. Here’s the whole list, in no particular order:

  • renamed Tick to Ticker
  • adding a listener to Ticker twice will now move it to the end of the listener list
  • added Ticker.getMeasuredFPS()
  • added Ticker.setFPS()
  • renamed Stage.tick to Stage.update and made Stage.tick point to Stage.update
  • made the pauseable param “true” by default on Ticker.addListener()
  • added Stage.toDataURL(backgroundColor, mimeType)
  • renamed Rectangle.w/h to width/height
  • improvements to commenting and documentation
  • formalized inheritance model to make code more readable
  • changed color to null instead of 0 in Shadow.IDENTITY
  • fixed an error with simple sprite sheets that weren’t set to loop
  • implemented “tiny” instructions for Graphics. (ex. myGraphics.f(“#0FF”).c(x,y,r) )
  • fixed problems with Graphics.clone()
  • fixed bug with passing instructions to a Graphics object constructor
  • complete rewrite of the render engine to be cleaner and more flexible
  • added .decompose() method to Matrix2D
  • added .skew() method to Matrix2D
  • added .skewX/Y on DisplayObject
  • added SpriteSheetUtils.extractFrame(spriteSheet,frame) method
  • added basic multi-line support for Text
  • added DisplayObject.suppressCrossDomainErrors property
  • complete rewrite of the hit testing system to be cleaner and run 5-10x faster
  • improved the interaction model:
    • added .onPress, .onClick callbacks on DisplayObject
    • removed .mouseChildren from Container
    • made .mouseEnabled true by default
    • added .onMouseDown, .onMouseUp, and .onMouseMove callbacks on Stage
    • added MouseEvent
  • Stage.getObjectsUnderPoint() has been moved to Container
  • added Container.contains(child) method
  • added DisplayObject.compositeOperation
  • added appendProperties() and prependProperties methods to Matrix2D
  • added DisplayObject.hitTest() method
  • added stage.snapToPixelEnabled and displayObject.snapToPixel
  • added DisplayObject.updateCache()
  • renamed minified file from easeljs.js to easel.js
  • Re-factored directory layout

Check out EaselJS.com for more info or to grab the latest build.

by Grant Skinner

Update on EaselJS v0.3

EaselJS v0.3 is going to be a very significant update. It will include:

  • a much faster (currently 10-15x) and useful / robust interaction model
  • improved code clarity, documentation, and comments
  • early tool support (ie. the start of an API to allow tooling to export EaselJS content)
  • multi-line text
  • a (theoretically) faster and more flexible drawing engine, with support for skews
  • a public GitHub repo
  • a large number of new features & bug fixes
  • release of a sprite sheet creation tool

I originally expected to have this version released this week, but I’ve broadened the scope of what I’m changing. Given that, I anticipate the release will push out to next week some time, but I’d like to believe it will be worth the wait.

I’m still accepting feedback on bug fixes or minor features for v0.3, and am very open to ideas for v0.4 (which is likely to focus on performance and bounds support).

by Grant Skinner

EaselJS v0.2 Released for HTML5 Canvas

I’m happy to announce that I’ve just released EaselJS v0.2. The focus of this release was on making drawing vector shapes and text to the HTML5 canvas easier with the new Graphics and Text classes. I also added Point and Rectangle classes, some new examples, put in support for multiple params on add/removeChild (ex. addChild(child1, child2, child3) ), added some minor fixes for mobile, and squashed a few bugs.

The next version of Easel will focus on performance improvements, architectural updates (finalizing an inheritance & event model), and improving/formalizing the mouse interaction model. I will likely put 0.3 up on GitHub, and open it for contributions.

As always, you can grab the latest version of the open source EaselJS library from EaselJS.com.