Modules

When writing a project with Bang you keep your code separated in modules. Each module exposes a Javascript Object, like a constructor function. The modules object is passed into each module definition, exposing your module to other modules that depend on it. Keeping your code in modules like this means you need only expose one global variable, the list of modules. Any modules loaded this way are essentially sandboxed in that modules object.
You define a module in a similar manner to RequireJS and the AMD:

The module system is another project of mine called Mod. I’ve written about it before. It’s very small and simple and it gets the job done (the job of code separation and later compilation).
Bang adds support for Google’s Closure Compiler to Mod, so once your project is ready to ship you can compile (in a sense), compress, obfuscate and pack your code down into a deployable script or a neato mosquito PNG. I like the PNG method because it’s slightly more obfuscated and adds further sandboxing, but that’s a topic for a later post.

It’s like Flash, but not too much like Flash…

Bang is enough like Flash/AS3 to be familiar, but sacrifices some AS3 similarities in exchange for simplicity and consistency. The complexity in Bang is very small. There aren’t any tricks to make it more Flash-like than it has to be and it won’t protect you from learning canvas operations. In fact, you’ll have to learn about the CanvasRenderingContext2D to do any real drawing. I’m not aliasing those calls and hiding it in a mock Graphics object for you! And you should be learning these new technologies without crutches. Think of Bang not as a set of crutches, but as a set of wings, or at least a hammer and chisel. No one likes masonry-by-hand.

It is fast.

The original pre-alpha version of Bang takes Douglas Crockford‘s extremism literally. There are no uses of the keywords ‘this’ or ‘new’. It accomplishes (multiple) inheritance through special constructor functions that add functions and closures to objects (or creates new ones). This, although a departure from AS3 at first, actually gives projects written in Bang an AS3++ feel. Multiple inheritance is awesome. Private variables are awesome. With prototypal inheritance you lose private variables so by using special constructor functions we can create private variables through closures. These features are awesome, but as Martin Hunt of GameClosure pointed out to me, it’s not fast. Processing time will go up linearly with the number of properties and methods created in the class. This means that if you’re creating a lot of complex game objects every frame tick, the project will likely start chugging. This is not fast. Apps have to be fast! For this reason I started a new branch of Bang that uses traditional prototypal inheritance. This branch will include a dirty rectangles implementation for really lazy redrawing, and I have plans for using WebGL for rendering down the line. Stay tuned!

A tiny demo

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]]> http://efnx.com/bang-pre-alpha/feed/ 0 http://efnx.com/as3-creating-a-convex-polygon-from-unordered-points/ http://efnx.com/as3-creating-a-convex-polygon-from-unordered-points/#comments Mon, 21 Sep 2009 23:24:58 +0000 Schell http://blog.efnx.com/?p=215 Let’s pretend you have an application that lets users create shapes to be used in a physics simulation and that the user must click on the screen to set the vertices of the shape. Many physics engines only support convex polygons, or shapes that don’t have inlets, bites, or coves, basically shapes that don’t have inward facing edges. With this limitation we have to be able to restrict [read as "guide"] the user to make only convex polygons. For this we are going to need an algorithm that takes an unordered set of points and finds the convex hull that encloses those points. This way the user can click and add points at random, if desired, and your program will keep track of what points create a convex polygon, while the others are thrown away [or dealt with however you see fit].

The Graham Scan Algorithm is a process of ordering a random set of points and then calculating jumps to the points in that set that constitute a convex polygon. In this algorithm there are three steps. First is to find a corner point, usually the topmost, leftmost point in the set. The second step is to order all other points by the polar angle between the corner point and the point in question. The last step is to traverse the set, taking each proceeding subset of three points (n, n-1, n-2) to determine whether the angle made by these three points is a left turn, right turn, or a straight line. If the turn made is our desired turn [which is usually left - but in Flash it's right, due to the flipped y-axis] then we add that point to the convex hull. If the turn is not our desired turn, we get rid of that point and move on.

Here is an example that shows first the data set drawn from point to point. Each successive line gets progressively whiter. In the second step we find the corner point, order the other points and then show the outer polygon.

Example

Here’s the code for the class:

We create a new GraphicsStroke [the line], a new GraphicsSolidFill [the fill], a new GraphicsPath [the path] and an IGraphicsData Vector to store them all in.

Now what we’ll need to do is populate the path with some commands and some points. To do this, we can use GraphicsPath’s familiar functions moveTo, lineTo and curveTo. These functions will fill path.command and path.data with commands and data, respectively. The parameters to each command are stored in the data array, where as a number representing each command are stored in the command array. You can read more about it here. So here is a function that will fill your path with points and commands to form a circle.

In this function _x and _y represent the center of the circle, r is the radius and path is your GraphicsPath. numPoints refers to the number of points you’d like to use for approximating your circle. The more points, the more “perfect” the circle will look, although more points will tax your frameRate. We can get a pretty nice looking circle with 8 points. 4 looks a little boxy, but around 8 is nice. Experiment. Here’s the next step – we’ll add the points to our path and then add the stroke, fill and path to our Vector and then have a sprite draw our graphics data:

This should draw 4 circle approximations of different resolution. This is what it looks like:

approximated circles

You can see that as n [numPoints] increases, the closer to an actual circle our object becomes. I hope this entry helps some of you out there save a little time.

Actionscript 3 Leopard GUI

The source and documentation are in their usual spots -> My classes. I’ll be updating them pretty regularly. Here’s the source for the project itself -> project source

Screen Capture of Waveform Plot

Thanks to the Summit Projects Flash Blog and Thibault Imbert at ByteArray for their posts on the different techniques that went into my class.

Source
Here is the source for my TextMate project: Sources
Documentation: class and event

And here is a Flex version (made in windows): // Thanks dem!
Sources (Flex version)

Digital audio in it’s rawest form [PCM wave data] is a long list of numbers from 1 to -1, which represent the sound’s amplitude. Another way of thinking about this is that each number represents your speaker’s distance away from it’s rest position. At 1 the speaker is fully extended, blowing out your ears and scaring your cats, while at -1 it is fully retracted, blowing out your ears and scaring your cats. To make a meaningful visual out of this we just set up a graph where time is plotted on the horizontal axis and amplitude on the vertical. So at a really high resolution, that might look like this:

Okay, maybe it would look like that if you were living in the 80′s. Or if you were really into oscilloscopes. In reality with most popular songs being two to five minutes long, we’d be looking at HUGE graphs. One three minute song sampled at 44.1kHz/s comes out to be eight million samples per channel. Per channel. Since most modern music is in stereo, we’re looking at two graphs now. So how do we compress this data and view it in a meaningful way? We cheat a little. We kinda scrap the whole graph/function thing. Well kinda. Let’s say you have a window 1000 pixels wide and a sound 3 minutes long. We have to compress enough samples together in order to represent them using each pixel [about 7,938 samples per pixel]. Averaging doesn’t work because with values oscillating between -1 and 1 the mean is usually zero. We could take one sample every so often to represent an entire chunk and plot that, but that’s just resampling at a much lower resolution, which results in aliasing and all sorts of bogus stuff. Take this video for instance:

Just instead of helicopter blades not moving, it’ll be your data points. No, instead what we do is we scan every single sample and pick out the largest and the smallest numbers from the chunk, which in our case means running through every 7,938 samples and picking the biggest and smallest ones. Then we plot them on top of each other, maybe with a line connecting them. Flash gets a little slow working with lists and arrays this big, but I’m sure we’ll figure out some neat tricks to get this stuff working fast. That said, here’s a little demo. If you can figure out the song I’ll give you a million bucks. [Let it chug for a while, Flash is a slow beast]:

pcm wave data plotted in flash

Project Source

ps – don’t cheat, guess the song before you download the source, goofball.

I’ve created a number of tools for people to use in the past, most of which I update regularly. In this post I’d like to revisit some of my old classes and post new updated code for those classes, as in their current form they don’t much represent my coding style. Please note that my class hierarchy has also changed, so make sure to update your includes if you are using these in your projects.

Button
I posted code for a button class here ->here about a year ago, since then I’ve changed things and really cleaned up that class. It’s simpler than before and faster. Given one to three images this class will create a clickable button that has the option to trigger up to four functions [on roll over, mouse down, mouse up and roll out]. Here is a snippet showing its use:

Calculating Frames Per Second
The next class I’d like to revisit is my FPS counter. It’s basically a textfield that displays an instantaneous fps count, and an averaged count. I have now removed the average frames per second and included a display of used memory in MB. Before I had used a timer to calculate the fps, which wasn’t quite accurate enough. Now the class uses flash.utils.getTimer() and is very precise and accurate. The class extends TextField so custom coloring, etc is very straightforward:

MultiLoader and MultiLoaderEvent
The next entry is a class created for downloading and importing files from your server or local file system into your flash application. It is what I use in place of my Multiple Bitmap Loader and my Bitmap Resource Handler. MultiLoader extends Loader to support multiple asynchronous downloads of images/swfs. They trigger specific (read “specially named”) ProgressEvents based on the names of entries supplied by you in their load functions. Alternatively, they also trigger a MultiLoaderEvent for every ProgressEvent or complete Event dispatched. One can access the bytesLoaded and bytesTotal for each event, as well as the entry name of the event (which matches the entry name given to MultiLoader). For example, to load a gif and listen to progress and complete events, code the following:

In this example my entry name is “efnx” and so MultiLoader triggers events of type “efnx_Progress” and “efnx_Complete”. By listening for these events, we can get updated information about our downloads. Another option is to listen for “progress” and “complete,” which will trigger an event of type MultiLoaderEvent, which extends ProgressEvent to include an “entry” member. The value of event.entry will be the name of the entry triggering the event, in this case “efnx.” Now to use our images we “get” the resource from MultiLoader, which has been storing it for us. A great feature of this class is being able to specify what the return type of your loaded object when calling the “get” function. Here I’m going to want to return a Bitmap object, so for the third parameter of the “load” function I’ll pass the string “Bitmap”. Here’s an example:

Now inside my efnxComplete function I’ll add the get function to get my Bitmap and display it.

Using the third parameter of the load() function is optional and if omitted Multiloader will by default choose an appropriate return type, here is a list of the valid strings to pass as a return type:

MovieClip
Sprite
Bitmap
BitmapData

If no third parameter is supplied, MultiLoader will return a type it thinks is appropriate, given the extension of the loaded material. For example loading a .swf will return a MovieClip, where as loading a .jpeg, .png or .gif will return a BitmapData.

Example App and Project Source
Here is a project that shows all three updated classes being used:

And here is the source to my classes:
Example Project and Source [includes classes]

Here is a little example:
updatedExample

And as always you can find the classes by themselves [along with all my other classes] here efnx AS3 classes, as well as some limited documentation efnx Class Documentation

The mouse position in x controls the frequency of a sine wave [from 220Hz to 440Hz or A3 to A4], while the y position controls volume. There’s some tearing that occurs when modulating volume, I haven’t figured that out how to fix that yet. As you move your mouse the wave that is generated is plotted on the stage. The pink dots represent sampled data points [which correspond to speaker movement] while the purple lines are approximations of the in-betweens [just lines drawn from point to point]. After playing with that for a while I wrote a class that matches note names to frequencies and drew markers indicating where on the x-axis of the stage one would have to place the cursor to generate a given note between A3 and A4. This is just a small example of the possibilities of sound in flash, and one way to interact with it. I’m looking forward to building on the classes I made for this example. I’ve included my entire TextMate project and source below [which will be the foundation of many more experiments], you can chop it up and use it however you want, although I didn’t copy any license to it, but trust me I won’t sue.

src -> Theremin Project/Visualizing Wave Data

1. Download installer from Adobe’s svn repository and select your OS [the rest of these steps are for mac, mind you, but you'll get the idea].
2. Unarchive and mount “Install Flash Player 10 UB.dmg”
3. Here’s the funny part, I couldn’t install the package. I got an error saying “nothing to install”, so instead, right click on “Adobe Flash Player.pkg” and choose “Show Package Contents”. It should show two archives, a plist, pkginfo and a resources folder.
4. Unarchive “Archive.pax.gz” to your desktop.
5. Inside you’ll find “Flash Player.plugin,” “flashplayer.xpt” and “version.txt.” The version.txt file says the player is version 9.0.45.0, but after looking at the info for “Flash Player.plugin” you’ll see it’s version 10.0.0.525, which isn’t the newest, but it traces and that’s what I need it for.
6. Copy “Flash Player.plugin” and “flashplayer.xpt” to your internet plugin folder, on my machine that’s /Library/Internet Plug-Ins
7. Restart FireFox/Safari/whatever.

That’s it!

I’m sorry if this info is un-needed, I definitely needed it, maybe everyone else can simply install that package, but I couldn’t, so that’s the fix. Happy coding.