Hello,
I red in some sources/answers different opinions about frame (in)dependent timers.
However when I’m running my timer on server - it’s actually depend on frames. I’ve compared it with delay node - which looks like independent on frames.
So my question - am I doing something wrong or Timer “Time” input node uses not seconds like it written?
If it’s really frame-dependent what alternatives I can use beside delays?
Hello,
Timers and Delays are not the same thing, and they shouldn’t be.
Timers are Frame-Dependent pauses.
Delays are Frame-Independent pauses.
That’s it.
Use Timers when the sequence of events matters.
Use Delays for random, untethered events.
(Aside: I’ve tested this, and these are the results I’ve come up with, because the documentation doesn’t seem to confirm or deny this.)
This is not true. The Delay node, which only works in blueprint event graphs, are a shallow wrapper on top of the underlying unreal engine timer system.
The real cause for the observed behavior, is that the unreal game loop is single threaded, and it will actually only execute your code “between” frames, during ticks. It renders a frame, then updates time to whatever “now” is, and then expires/fires any timer or delay that would have expired up to this new “now” time. So, the jitter of when your timer/delay happens, is dependent on the frame time of the frame right before it happens. However, the overall duration is not frame rate dependent – if you set it to 3.5 seconds, it will happen after 3.5 seconds plus maybe a little bit of jitter, no matter whether you run at 10 fps or 100 fps.
And would this occur with a delay as well(?), because that means I misinterpreted the jitter as a frame dependence.
I didn’t have that issue with the delay, but I want to know if you have.
Delays just run inside the main game loop, like any invoked event.
If you set a delay for 0.01 seconds, and your frame rate is 10 fps, your delay will actually continue after 0.1 seconds.
Okay, then I stand corrected.
Thank you, but how you will explain that 1 second of Delay equals to 1.7sec of Timer in my example? And when I changed engine fixed FPS - timer also was affected by this - but delay not.
Hi, are you sure your TESTDelay variable is not set to 1 by default? As I would definitely expect 1 second timer to take something around 7 x 0.1s delay, but not 17 x 0.1 delay.
This is because of the thing explained above, delays end a frame after passed time.
Yes, I’m sure. I’ve recorded video comparing looping Timer with interval 0.1s vs Delay. Both increment their values by 0.1 every 0.1 sec.
The timer and the delay may run in different run queues, but they are both run in the main thread, serially, between individual rendered frames. The exact way they calculate the game time at which to run, seems to vary. I agree it’s a bit surprising, but neither timers nor delays are real-time accurate features.
Thanks for this, because I thought I was losing my mind.
Again, I’ll take J’s word for it, but I had this same result.
Ah well.
This is more than a bit surprising. Also, I cannot reproduce it.
As far as I can tell, looping timer will always trigger more often than a Delay-loop of the same interval.
This is because looping timers look back in time, can trigger multiple times per frame if necessary, and apply overtime to the next interval. For example with a looping timer of 0.1, if a frame takes 0.4s then the timer will trigger 4 times at once.
Delays on the other hand are like timers with no looping, so they’ll trigger once the interval has passed, and the extra frametime is lost as jwatte said in first post. So little by little the Delay-loop will derive away from the looping timer.
Example Timer :
Example Delay :
Running both gives me same expected results - I cannot reproduce your issue.
Thank you,
I tested on Listen Server and was playing with Fixed Frame Rate of engine in Project Settings.
