Re: CoreAnimation with and manual animation...

FROM : Jesse Grosjean
DATE : Wed Apr 02 00:54:21 2008

Jens,

Thanks for your reply.

What I'm doing now is something like this:

   [CATransaction begin];
   [CATransaction setValue:[NSNumber numberWithFloat:0] 
forKey:kCATransactionAnimationDuration];
   
   for (CALayer *each in [rootLayer.sublayers copy]) {        
       [each step]; // calculate and assign self new position
   }

   [CATransaction commit];

I've also looked at the physics engine stuff, looks like great fun, 
but this project is actually super simple so I probably won't bother 
with including a physics engine for now.

Jesse

On Apr 1, 2008, at 6:17 PM, Jens Alfke wrote:
>
> On 1 Apr '08, at 10:44 AM, Jesse Grosjean wrote:
>

>> n my app it seems like it would be simpler to just setup a timer 
>> and just directly update the ships position based on it's velocity 
>> for each time interval from my timer. I'd still want to use the 
>> built in core animation animations for other properties such as 
>> transparency, filters, etc. But for layer position it seems like it 
>> would be easiest to control that directly...

>
> You're right. Last year I was fooling around with hooking CA up to a 
> 2D physics engine, and I just let the engine tell me where and when 
> to position the objects, and set their position properties 
> accordingly.
>
> For best results, disable animations for this, otherwise CA will try 
> to interpolate positions and things won't move correctly. I was 
> doing this by using a CATransaction to disable all animations, but I 
> think in hindsight it might be better just to to adjust the layers' 
> animation dictionaries to clear out the animation for the "position" 
> key.
>
> (Using an existing physics engine is a great way to go, if you want 
> to do this. I was using Box2D, but there's another similar one 
> called Chipmunk. The math for this stuff gets really hairy — I've 
> just started reading "Physics For Game Developers", and it's 
> fascinating but I'm so glad I don't have to implement that myself!)
>
> —Jens