Papervision 3D Framerate

Let us share some constructive hands-on tips or trix on how to increase framerates. There's a lot of design issues from modeling 3D-objects to bind them to value-/business objects (classes). However, you should also take the rendering principals of the Flashplayer and your 3D-API in consideration! The gems in this topics may be, in no particular order, under clever headlines, so feel free to contribute by comments.

1) Override Flex default framerate of 24 by setting the desired framerate Application property in *.mxml (haven't got it to work from CSS). Try framerate 60, and hope that the Flashplayer may reach the fps of 40 once in a while.

2) Ask your self when and why you need to run onEnterFrame()! Even for a design built with constant movement in mind, it is a good strategy to provide for situations where a 3D world is allowed to freeze for a couple of seconds. If you can make it freeze without the user notice it - good for you. You will need that time to load additional assets or resources.

IMPORTANT!!! Try NOT to use onEnterFrame() at all in your 3D viewport rendering engine! Try the Timer intervall instead. And above all - try NOT to use two or more onEnterFrame()-callbacks in parallell, that will probably sink you application framerate below 10 fps.

In PV3D all DisplayObject3D have a pointer to the scene or context they belong to. Therefor you may choose to use the Scene object as the eventdispatcher for such events as PLAY and STOP to control when to stop or run the onEnterFrame.

3) If you know, or if the 3D object or face itself know that it should be invisible - set its visibility to false. In that way the the culling process does not even need to calculate.

4) Z-depth and culling calculus are process intensive. One finding I had was with a cube, or rather six individual planes, with no awareness of eachother, in a group forming a cubelike shape. I wanted to keep the cube in constant movement of a Perlin noiced sine function in each degree of freedom (DOF). The cube was rotated with in a slow wobbeling motion showing the same three faces to the camera, two sides and the rooftop. I found that the framerate decreased when one face - the rooftop - had it's normal almost perpendicular to the camera. The more the rooftop pointed it's normal direction towards the camera the framerate increased.

Thus, a large surface with a tiny projection to the view plane is more computationally heavy than when the same side projects more of its surface to the view plane! By rotating the default angle of my cube slightly, the culling did not kick in, and I increased the framerate by two times.

5) Over all for FlashPlayer rendering, check how Bitmap Cache Policy can be used in your project..

3D General

Let's talk about how to optimize 3D for Flex. Keep it low poly, and simple texturing to allow more cpu and framerate. You will need the power for animation in both 3D viewport and 2D. There are several 3D API's and their offsprings for Flex/Flash developers out there. I tried Sandy, but got stucked with Papervision - in the summer of 2008 the branch GreatWhite Effects. Whether they are called GreatWhite, Away3D or anything else I believe in general that it really doesn't matter which one you choose. You should try them all, but you can't be an expert on all of them, and you should choose the one targeted to solve your specific problems or design needs.

3D on the web is not to be compared to modern 3D technology for film effects, computer games, or game consols! The open source community mentioned aboved are doing a tremendous job putting effort into making the API's both stable and effectfull, but as long as it is all about software rendering we must consider following when starting a new project:

a) From a technical point of view, keep it simple shading, low poly, and light-weight texturing!
b) From a design point of view - are you sure 3D is going to add to user experience at all?

These are two mayor considerations when first meeting your client. You don't want to end up with a disapointed client stating that you did not live up to their expectations!

... to be continued

AIR Garbage Collection and Memory Leaks

Summary: Following insights came to me when debugging a new AIR application that was built to be used as a printing service, polling a database for printjobs, setting a timeout and then repeatedly poll again. Using Flex Builder Profiler showed first an obvious memory leak as several of the project classes increased in number of instances over time. This resulted in a crash of the Air Debug Launcher (adl.exe). However, after fixing the obvious by best practise as described below, and verifying that the Profilers memory profile was kept constant, I found that the total memory usage given by the Profilers analysis was NOT the same as the trace of flash.system.System.totalMemory!

Best practise in programming AS3, whether you are hacking *.as classes or *.mxml, should always use a destuctor function. Let us use the same convention as for the good example of the BitmapData class, and call it dispose():void. That will also make good sens to you .Net hackers for the same reason. The BitmapData.dispose() function frees memory for garbage collection.

You will have to make sure the dispose functions are called when instantiated objects no longer are in used and need to be referenced. Creating a new Array() of objects, running ArrayCollection.removeAll(), or setting each object to null does not guarantee garbage collection. References within the objects still may be held by listeners and/or other classes.

For *.mxml you will most likely use protected functions as onCreationComplete():void and onAddedToStage():void to do some initialization, bindings, and listening - just as with the class constuctor. Just make sure you also declare a public function dispose():void that eather can be called internally by a remove event, or externally by any controller or command. The function may look something like this:

public function dispose():void {
bitmapData.dispose();
swfLoader.loaderInfo.loader.unload();
removeListener("type", callbackfunction);
CairngormEventdispatcher.getInstance().removeListener(
  "type", callbackfunction);
file.close();
... and so forth
}

Being consequent and thorough will also give you the possibillity to force garbage collection once in a while between two frames by doing the following:

private var gcCount:int;
private function startGCCycle():void{
gcCount = 0;
addEventListener(Event.ENTER_FRAME, doGC);
}

private function doGC(evt:Event):void{
flash.system.System.gc();
if(++gcCount > 1){
   removeEventListener(Event.ENTER_FRAME, doGC);
   clearTimeout(timeOut);
   timeOut = setTimeout(lastGC, 50);
}
}

private function lastGC():void{
clearTimeout(timeOut);
flash.system.System.gc();
}

Thank you Grant skinner. Read more:
www.flexdeveloper.eu
blogs.warwick.ac.uk
www.gskinner.com

AIR and the pitfalls of the Security Sandbox (and eternal damnation of Singletons)

For a few days now I've been working on an AIR application to generate XML for a product called Sound Manager. Sound Manager, which we built for a client of ours - DinahMoe, is a pretty nifty system which allows them to hand over a couple of as-files to their clients through which the end client's developers can dispatch events describing what's going on in the Flash app. DinahMoe can then orchestrate sounds for the app by linking the events to actions playing, stopping, pausing, transforming, jumping and so forth, in sounds.

In order to lower the complexity for the end client, we put all the code that actually does anything into the sound libraries that are compiled by the guys at DinahMoe (or is it just guy, Johan?). The objects in the sound libraries then listen for the Sound Managers events and do what has to be done... and what has to be done is off course described in XML.

So the AIR admin lets DinahMoe build the XML through a rich interface where actions can be categorized in folders, copied, edited and so on. Then it was time for the testing. In short, I wanted the AIR app to instanciate the SoundManager, tell it to load the XML and the sound libs and then fire the events I wanted to test. Here's where everything goes pear shaped. The AIR app lives in the Application Sandbox, the loaded swf:s liv in the Loca file Sandbox. So they each instanciate their own singletons and all communication is lost.

So I built a swf which instanciates the SoundManager, and let the AIR app load the SWF... but as it was placed inside the apps application directory, it was too run in the Application Sandbox. So I copied it to the same directory as the Sound libraries that were to be loaded... and now they all ended up in the same Sandbox... but still they could not communicate. And here's where I lost hope. So now I return handles through the SoundLibraries and call each and everyone of them with each event. Not pretty but It's the best I could com up with.

So what is the deal? Are SWF:s in the Local File Sandbox prohibited from talking to each other? Is there a solution? Anyone?

All Your Base Are Belong To Flex, Flash, AIR, .NET and such

Here we go. This is the official All Your Base blog for sharing our wisdom and experience in developing RIA:s with Flash, Flex, AIR, .NET and all other things cool and nerdy.