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PixelBender for game developers
This week I found the time to take a look at PixelBender. And of course my first thought was, how to use it in my next game.
In praxis PixelBender is used for two thing. On one hand it's used for what it's supposed to - visual effects. On the other hand it's used for calculation. In this post I am talking just about visual effects.
For my games in the past I used movieclip animations for visual effects. With visual effects I mean brain death effects. That means the effect is played and doesn't have any back coupling to the logic or the game environment. That's nice to use, because you trigger the effect and don't have to care about the rest. The movieclip removes itself from the stage with a short script in the last frame.
This mechanism had got the following characteristics:
- Effect has to be easy to start.
- The effect should be animated automatically.
- When the effect is finished everything should be cleaned up automatically.
For PixelBender effects I wanted a mechanism doing exactly the same, but things are a bit more complicated.
- For flash games all recourses should be compiled into one swf. There are some issues to get the PixelBenders effect into the swf file.
- PixelBender effects are not designed to be animated.
- The filters array of the Displayobject object is not able to be manipulated.
Getting PixelBender effects into the swf file
Exporting the PixelBender kernel in the PixelBender toolkit created a .pbj file. This file is used by the flash player at runtime. There are three methods get the .pbj file into the swf file.
1. loading at runtime
I will not discuss this solution here, because it isn't practical for flash games. Flash games are mostly spread over a lot a sites and servers. You would need your own server to store all your effects, what would cause a lot of traffic and work to maintain.
2. [embed]
The embed tag allows you to embed the .pbj file into your swf file. There is just one drawback about it. The embed tag in not part of the AS3 specifications, it's part of the flex framework. So, if you use this tag the flex framework is involved.
3. PixelBender to Actionscript converter
I have found this tool, that converts your .pbj file into an actionscript class containing the .pbj file as a byte array. With this method the .pbj file is embedded into the swf file without involving the flex framework. But there is a drawback too. This method makes it necessary to convert the .pbj file newly every time you change it.
http://blog.brun.pl/2008/05/pixel-bender-pbj-file-to-actionscript-class-converter/
I decided to use the embed tag in my class, because from my point of view it's the best solution.
I won't explain the source of the classes here. They should be easily understood and where it's needed the source is documented.
The main class is the effectManager. You have to call it's main function in your main game loop. You may now ask why I didn't use timer objects for the animations. The solution is simple: I design all my programs to be driven by one force based on the ENTER_FRAME event. It's simply easier to handle.
In the download file you will find the logic for the effect management, an example PixelBender project and an example how it's used in the swf file.
download: pixelbender1.zip
- package {
- import classes.at.lueftenegger.effects.EffectsManager;
- import classes.at.lueftenegger.effects.fx.ShockWave;
- import flash.display.Sprite;
- import flash.events.Event;
- import flash.events.MouseEvent;
- public class Main extends Sprite{
- // Embed is not part of the AS3 specification.
- // It's part of the Flex framework.
- // So this framework is involved here,
- // but there is no other solution.
- [Embed("./assets/shockwave.pbj", mimeType = "application/octet-stream")]
- public static var fxShockWave:Class;
- private var _fm:EffectsManager;
- public function Main(){
- _fm = new EffectsManager();
- addEventListener(MouseEvent.CLICK, doShockwave);
- addEventListener(Event.ENTER_FRAME, main);
- // you have to write a Class implementing IEffect for every single effect
- // you create in your game.
- // This line gives the effect class a reference
- // to the embeded pbj file
- ShockWave.effect = fxShockWave;
- }
- private function doShockwave(e:MouseEvent):void {
- // this line of code triggers the effect. That's all you have to do.
- _fm.AddEffect(new ShockWave(stage.mouseX, stage.mouseY), image);
- }
- private function main(e:Event):void {
- // game main loop
- // ... your game runs here
- // in your game main loop call the effect manager's
- // main function to run the effects.
- _fm.main();
- }
- }
- }
