How make a game loop on the iPhone without using NSTimer

Question

In order to cleanly port my game to the iPhone, I\'m trying to make a game loop that doesn\'t use NSTimer.

I noticed in some sample code that, if using NSTimer, you\'d s

Answer 1

Regarding CADisplayLink and the Doom for iPhone article by Fabien, I emailed Fabien and I think the best option is subjective. Performance-wise DisplayLink and triple buffering should be the same, but DisplayLink is only available on > OS 3.1. So that should be your determining factor.

Answer 2

Another option with iPhoneOS 3.1 is to use the new CADisplayLink api. This will call the selector you specify when the screen contents needs to be updated.

displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(renderAndUpdate)];
[displayLink setFrameInterval:2];
[displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

The new OpenGL project template in XCode also use the CADisplayLink if you need some more example code.

Answer 3

If you don't wish to use NSTimer you can try running the NSRunLoop manually:

static BOOL shouldContinueGameLoop;
static void RunGameLoop() {
    NSRunLoop *currentRunLoop = [NSRunLoop currentRunLoop];
    NSDate *destDate = [[NSDate alloc] init];
    do {
        // Create an autorelease pool
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        // Run the runloop to process OS events
        [currentRunLoop runUntilDate:destDate];
        // Your logic/draw code goes here
        // Drain the pool
        [pool drain];
        // Calculate the new date
        NSDate *newDate = [[NSDate alloc] initWithTimeInterval:1.0f/45 sinceDate:destDate];
        [destDate release];
        destDate = newDate;
    } while(shouldContinueGameLoop);
    [destDate release];
}

Answer 4

While using CADisplayLink is a really good alternative for 3.1 based games,
anything using "Timer" is a really bad idea.

The best approach is the good old "tripple buffering" to decouple the GPU work.

Fabien has a very good explanation in his Doom Iphone review:
http://fabiensanglard.net/doomIphone/

Answer 5

Take care using self as a target for displayLinkWithTarget, the manual says "The newly constructed display link retains the target". Martin