Posts Tagged object pooling
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 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.
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.
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…
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%.
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.
I know that for every project I say that it was the most complicated one that I did, but this one really was the most complicated I ever did. There even was a night where I didn’t sleep because I wasn’t sure I could make it happen.
My big challenge was to create an experience that was close to what the design team was imagining but that wasn’t too CPU intensive (like all my other projects). I think I did manage to do that. It runs pretty smoothly even on some bad computers. I let Papervision3D do all the heavy lifting but I kinda trick the user into think that there are a huge load of dominoes while at any time there is only 300 of them max (you could consider this object pooling). A second challenge was to position those 2400 dominoes so the they make the final path. The design was done in Illustrator so what we did was that we exported the .AI file as a .SVG file. SVG is just an XML so I made another program that would read the SVG and output (trace to the console) ActionScript code that I would paste into the main application. Finally, the last challenge was to show a zoom out with all the dominoes fallen revealing the message. As I said earlier, if I had 2000+ dominoes at the same time that would be too hard for the computer and run really slow. So I replaced the scene with a bitmap. To get that final bitmap I had to make yet another program that would render me the final path with all dominoes fall and that a screenshot of it.
So I ended up doing 2 more ActionScript projects to end up with the finished product: The Holiday Humanoes.
Oh yeah, just a little trick to finish up, when you deal with COLLADA models, make sure your 3D guy exports the model without the textures if you don’t want the Flash Player to query the server each time you create a DAE. That is what was happening at first and it really scared me.