cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   ddeaco
   Member

   Hi,

   I need to time players in a section of my game, but how do i create a timer that isn't linked to the frame rate.

   My first thoughts would be doing something like this

   - (id) init{
   	[self schedule: @selector(tick:)];
   	[self schedule: @selector(timer:) interval:1/60];
   	return self;
   }
   
   -(void) timer: (ccTime) delta2 {
   	time++;
   }
   -(void) tick: (ccTime) delta {
   //do game stuff
   }

   But the time is still not running in real-time. I'm sure there must be a simple solution.

   Thanks in advance,
   Dave

   Posted 2 years ago #
2. 

   hactar
   Member

   Not quite sure I understand the issue, but I'll try none the less.

   The iPhone is not a real time system, as such you cannot create a timer that is guaranteed to go off in a particular interval. It does its best though to meet your settings. The above code is a cocos timer, and it provides you with delta, which is the amount of time since the last tick occured. You can use this to calculate how much time has passed:

   -(void) timer: (ccTime) delta2 {
   	NSLog(@"%f seconds have passed since the last time this function was run", delta2);
   }

   By adding up these fractions of a second you therefore also know what the total time is since the timer was launched.

   A different approach would be to use an NSTimer (see the iPhone sdk documentation). This allows you to set an interval, but again this will only be a best try by the iPhone, it may be off by milliseconds. This approach also has the disadvantage that if you pause the ccDirector, your NSTimers will continue to fire, so parts of your game will continue running while others are paused.

   Posted 2 years ago #
3. 

   Questor
   Member

   ddeaco/hactar,

   I don't know the solution to the problem but I have seen this behavior as well.

   For example create a timer that runs as often as possible (no interval specified):
   [self schedule: @selector(tick:)];

   then in the tick method, print the delta time passed:
   

   -(void) tick: (ccTime) dt
   {
         CCLOG(@"Delta Time: %.4f", dt);
   }

   Now if you run the above code at a frame rate (animation interval) of 1/60 you will get a tick (on average) about every 0.0166 seconds. If you then change the frame rate to 1/30 and run it again, you will get a tick (on average) every 0.0333 seconds.

   So it appears the schedule/tick interval is somehow related to the frame rate. Note: I am not saying this is a bug, just saying it is what I have experienced.

   Also, there is a (very long and somewhat) related discussion about game-loops/timers, etc, over at the apple developer forums:
   https://devforums.apple.com/thread/16515?start=0&tstart=0

   Regards,
   Q

   Posted 2 years ago #

RSS feed for this topic

Reply

You must log in to post.