UPDATE: This post is here for historical purposes. The SWF has been moved to a new location.
I’ve been messing around with particles, particularly the blitted, traily kind I guess. Click on the image below to pop and watch it. Grab the source at the bottom and let me know if you do something cool with it.
The particle trails you see are actually all on one bitmap that I draw to after updating each particle in sequence, per frame tick. The particles themselves are a simple class that keeps track of a few variables such as velocity and position. The class doesn’t extend anything, instead the Main class of the swf draws a line from where the particle was in the previous frame to where it is in the current frame.
To make them fade over time I simply did a colorTransform on the whole bitmap at the begining of the tick method. I didn’t alter any hues obviously, I just subtracted the alpha value of the bitmap a little. So the longer the pixel has been in the bitmap, the lower it’s opacity. I wish I can claim that cleverness but I actually got the idea from somewhere else… probably 8bitRocket.
This method of graphics manipulation, called blitting, is the way to get a metric fuck-ton more performance out of Flash than is possible with mere Sprites. You can see there’s 600 “particles” in the demo — had I simply extended the Sprite class and used that to render the scene, I probably would have only been allowed a few hundred sprites while keeping the framerate at around 30.
If you want to see some great examples of blitting, check out 8bitRocket’s posts on the subject. You can even find a blitting engine called PixelBlitz — check out this badass schmup demo of his!
