PixelBlitz first hands-on

Norm Soule has released the first version of PixelBlitz, his 2D AS3 library that’s geared towards helping you create fast 2D “sprite” based games. I’ve had a good play with it today and this is definitely one to keep an eye on. It allows you turn any movieclip into a PixelSprite, which is essentially an extended bitmapData object upon which you can perform pixel accurate hit detection. PixelClips are similar to sprites except you have rudimentary timeline controls which are useful for animations.

PixelSprites/Clips are then added to a RenderLayer. Items in the Render Layer can be z-depth sorted, have effects applied to them, and be set to enable parallax scrolling. There are 4 effects in the current build, including trails, glowing, fog and a grid effect. To be honest they’re not a massive deal of use as they exist due to the speed hit involved, but you can easily customise them as you see fit.

RenderLayers (and you can have more than one of them) are added to the 2DRenderer, which does all the donkey work and needs to have its update() method called each frame.

This is just the first release, so I’d expect some changes to happen internally, driven by design decisions made post-v1. The system is nice and fast (when you don’t mess with the effects at least!) and is a good starting point if you’ve never worked like this before. It does have some serious limitations though, for example the PixelSprites cannot be rotated, scaled or have their alpha set. You also can’t use masks on them, which is a great shame. I believe this is mostly due to PB internally using the bitmapData’s hitTest method, which itself cannot handle scaled or rotated bitmaps.

It’s lacking in other areas that would make it truly useful right now – for example there’s no way to quickly check for regional collision (i.e. a quad tree system) which means you’re performing pixel level collision on every single object, against every single other possible object and you need to create your own functions to avoid this. As PixelSprites extend the EventDispatcher base class of all things (a truly strange design decision imho!) you don’t have access to methods like hitObject that could speed this up for you.

I’m not knocking the release – it takes a brave developer to throw a library out to the wolf packs of the internet – but I do feel it certainly needs further work before it becomes truly useful for a full game. I’ve already contacted Norm to offer my help, if you’re reading this and would like to see PB turned into a really killer library, then it would be wise to do the same!

Posted on August 27th 2008 at 6:15 pm by Rich.
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