Optimizing Flash for the iPad

You might know that I am making a game for the iPad and it’s nearly done. The thing is, I also want to publish it on the web, you know, make money from sponsorship too. Actually, I think it might be the only way I make money with the game as the iPad app market seems really hard. Plus it will also cost me money to publish in the Apple app store (developer account), so I think I might be loosing money going that way. Anyway, I was testing my game for the web first and everything was working fine. I tested on the iPad after and that is when things started to get hairy.

Yeah, an iPad (iPad 2) is not a full fledged computer (funny to say this considering my first computer was a 486), so it is not as fast. Well I have seen some pretty crazy shit on the iPad, like the Dead Space game so I guess it can be pretty strong. This only means that the Flash player isn’t that great on it, probably because it doesn’t use the GPU. So as I was testing my game on the iPad, it started out working really great, but as the game went on, more and more objects got drawn onto the screen and that is when the performance started to go down. So I set out to optimize my code.

Object pooling

Object creation in Flash is an operation that is costly and since I hadn’t optimized anything yet, I was recreating every object on the screen every frame. There is a possibility of having 240 objects on the screen at the same time, so that’s a lot of object creating every frame. To minimize this, you can do object pooling, which is having a pool of already created objects and change their properties instead of creating new ones. I did just that and it went really fast to implement. The thing is, when I tested it on the iPad, it made no difference at all.

Blitting

Another thing that is heavy on the CPU in Flash is updating graphics, so I tried to optimize that part. Blitting is a technique by which you compress all your visual into only one Bitmap that you draw on the screen. So instead of having multiple display objects being redrawn (in my case 240), you only have one. Read more about blitting here. Blitting doesn’t fit well with every project (like those relying on vector graphics) , but mine was based on Bitmaps and didn’t have a lot of rotations (it did, but only 90 degrees one) so I could easily do it. I was pretty sure that this would help a lot, but it actually did nothing noticeable. I was a bit baffled here, maybe my redrawn zone is too big… It is a game for iPad so I have a full resolution of 1024 x 768, maybe that is too heavy for the Flash Player.

Code Optimization

So if it wasn’t the creation of objects or the graphics, than maybe it was the code. I had used Arrays everywhere cause it is just simpler to use than Vectors, so I changed them all. I also did some loop optimization and replaced some divisions by multiplications ( like /2 to *0.5). Also didn’t change anything…

Last Resort

My last resort was to change the game dynamics so that the game is less intensive on the CPU and that is the only thing that made any impact on performance. My game is a puzzle, so I removed 3 rows and 1 column from it thus reducing the possible maximum number of object on the screen (and also the redrawn region size, and probably also the number of computations) by 20%.

Conclusions

I’m pretty sad at this point, changing the game dynamics to optimize is not a really good decision, it’s kinda like saying let’s make the game less fun to make it run faster. What I liked about Flash is that I could compile for the web, iOs and Android with limited changes (in this case all I changed was different layouts based on size (height and width) of the game). Turns out it is not fast enough on iOs (iPad). Maybe when they put Stage3D on iOs that will do it, but till than there is no true cross development platform. I meant to look into Corona, but it does only mobile. And I really don’t want to fall into the HTML5 mess. I would really like to hear about a dev story about HTML5 and a game built for web and mobile and most importantly how much time it took to do.

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  1. #1 by jim - January 19th, 2012 at 06:54

    try haxe nme, they facilitate cross platform dev pretty damn good and with a as3 like syntax.

  2. #2 by Miguel Moraleda - January 19th, 2012 at 08:52

    Hi,

    Are you working with PNG or JPG images ? PNG works much better on the ipad, because they really use GPU. I recommend you try to use all your images as PNG and set your flash to use GPU mode. Remember to set as loosless on Flash to.. and never compress the images to jpg.

    Best regards,

    Miguel

  3. #3 by Mat Janson Blanchet - January 23rd, 2012 at 12:07

    I haven’t tried it personally, but how about looking into Starling (http://www.starling-framework.org/) or ND2D (https://github.com/nulldesign/nd2d)? Would leveraging the GPU with these be possible if you target iOS?

  4. #4 by zedia.net - January 23rd, 2012 at 14:20

    Starling and ND2D both use Stage3D which can’t be used as of yet in AIR for mobile. Really hope they fix that soon.

  5. #6 by ArcadeHype.com - June 7th, 2012 at 11:26

    I recommend you read the book Flash for iOS apps cookbook. It greatly clarifies how you should develop for mobile with Flash CS 5.5 and Air for iOS 3.2. Ive been running tests on my iphone 3gs and im cranking out 200 sprites on screen with 30 frames of animation in each sprite (all blitted) and im getting a solid 45fps. The book outlines exactly what you should avoid doing and how to optimize your code efficiently.

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