Created by Leonhard Lichtschlag (leonhard@lichtschlag.net) on 9/Feb/12.
Copyright (c) 2012 Leonhard Lichtschlag. All rights reserved.
Dazzle is a demo of some effects one can do with Core Animation in iOS 5 with the CAEmitterCell and CAEmitterLayer classes:
- The "info" tab shows a linear emitter with a shadow applied to all cells to create an emboss effect.
- In the "hearts" tab the emitters are triggered by an animation to create the "burst" animation.
- In the "fire" tab, additive overlaying of cell creates a somewhat realistic impression of fire. The source code here has been adapted from the corresponding Apple sample code for Mac.
- In the fourth tab, I show how emitted cells can in turn again emit cells: the triangles sent away from the touch send two kinds of cells sideways and back to the touch location. The emitted cells start with their visual values set to those of their parents.
- Emitters can also be invisible, but there seems to be a bug in CAEmitterLayer: setting the birthrate lower than 1.0 creates huge spawn rates even though it should be less. To still create the fireworks with it, the explosion can therefore only happen at most 1 sec after the rocket launches.
Performance-wise, setting the flame height to maximum will really stress the iPhone4's graphics to its max, resulting at about ~30 fps. Likewise a constant triggering of new touches in the frouth tab will average at about 22 fps.
Update: In iOS6 the behaviour of the birthrate property seems to have changed, a fireworks explosion is triggered at t= 0s. This is no longer the case in iOS7.
Update: In iOS7 the behaviour of the birthrate property seems to have changed, it now acts as if the objects would have been spawned in the past... (rdar:14413481)