Sprite spawning at wrong time

I'm not sure what I'm doing wrong here, but I can't seem to get the sprite to spawn at the correct interval.

I have some events that add 0.1 to a global variable every 0.1 seconds. This lets me reset the timespan when a level restarts. At 0.3 seconds I spawn a new sprite, which works fine. But as soon as I pass 0.7 seconds mark, sprites start to spawn with a 0.1 second delay.

<img src="http://i.imgur.com/8VIAU.png" border="0">

Sample Capx

Even stranger, while the 0.3 above appears to work if using >=, this does not (the sprite never spawns):

<img src="http://i.imgur.com/n2Rfq.png" border="0">

Sample Capx

Can anyone spot what I'm doing wrong? It seems this should be working <img src="smileys/smiley5.gif" border="0" align="middle">

Computers cannot represent 0.1 exactly in binary, so a very close approximation a little less than 0.1 is used. That difference increases every time 0.1 is added.

One solution would be to replace the TimeSpan=0.8 condition with:

System Compare abs(TimeSpan-0.8) < 0.0001

Another would be to only add integers to TimeSpan and set the text to TimeSpan/10.

A final idea would be to instead of adding to TimeSpan every 0.1 sec, add dt to TimeSpan every tick and set the text to int(TimeSpan*10)/10.

Setting text to a number rounds the number (to 5 decimal places) which is why it looks like it should be working. Set your text to str(TimeSpan) and you'll see what's happening.

Setting text to a number rounds the number (to 5 decimal places) which is why it looks like it should be working. Set your text to str(TimeSpan) and you'll see what's happening.

OH, that makes sense. I wasn't aware that it rounds it. That's a little annoying =/

R0J0hound: I'll give the dt trick a shot. I can't remember exactly why I didn't do that, I remember running into some weird timing problems but I can't for the life of me remember what they were. I'll give it another try and see how it goes.

My question is why are you changing the system time scale? and do you need to judge your time differnce as you are?

I suggest using something like this.

dl.dropbox.com/u/14087254/wierdtimebug.capx

also keep in mind when you have a constantly incrementing value try to compare with <= or >= not just =.

jayderyu: Changing the timescale was just so I could demonstrate the oddity I was seeing, without the numbers flying by in milliseconds. As for why I'm recording it to a variable, it's so that when I restart the level (when the player dies) I can reset it back to 0.

R0J0hound: I remember the issue I had originally. It was that when I was using dt I was finding it hard to say "every 0.3" because it was rare for the dt to match - it would jump from "0.29897" to "0.31102" and my statement would miss. I thought that by just saying "every 0.1 seconds add 0.1 to my local (and reset-able) timespan" I got around that. I didn't realize it was having the exact same affect, but it was just rounding for me!

I think I've learnt a little bit more about how time works in games. I tells ya, I think understanding time and framerates is one of the trickier subjects to get your head around as an amateur game developer <img src="smileys/smiley9.gif" border="0" align="middle" />

About your dt issue, you can do an "every x second" this way:

+Every ticks 
   -> add dt to timer 
+timer >= x 
   -> substract x from timer 
   -> do things