Problem with Time based game (tick counter's acting wierd.. )

08-03-2006, 05:24 PM

RonenNess

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Join Date: Mar 2006

Location: Israel

Posts: 150

Problem with Time based game (tick counter's acting wierd.. )

hi everyone.
im working on an rpg game engine, and im having a problem with the time based system.
i got like this :

Code:

'world time stuff
Private Declare Function QueryPerformanceFrequency Lib "kernel32" (lpFrequency As Currency) As Long
Private Declare Function QueryPerformanceCounter Lib "kernel32" (lpPerformanceCount As Currency) As Long

'time system stuff
Dim Freq As Currency
Dim StartTime As Currency
Dim EndTime As Currency
Dim TimeElapse As Double

and in my main loop i have this :

Code:

Do While Running = True
 QueryPerformanceCounter StartTime

' all the game stuff comes here...

    QueryPerformanceCounter EndTime
    QueryPerformanceFrequency Freq
    TimeElapse = ((EndTime - StartTime) / Freq)
DoEvents
Loop

so now i basicly have "TimeElapse" which should be the time passed between eatch frame.
so i suppose to double everything in that value, right?
like Player.x = player.x + speed.x * TimeElapse

Now, the wired part is.. its somtimes work fast, and sometimes works really slow.. and i dont know why...

i mean, it sould work fine, and always at the same speed...
thats the whole idea of it now isnt it?
im using DX btw, maybe it has anything to do with it.

so anyone knows what can somehow effect the speed, or what im doing wrong?

thanks.

08-04-2006, 01:44 AM

AdrianDeAngelis AdrianDeAngelis is offline

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Join Date: May 2005

Location: Australia

Posts: 549

1) Are the variables you multiply by TimeElapse single or greater precision? If Speed * TimeElapse is really small then it will look like things are moving fast/slow... that is the most obvious thing I can think of

2) No the TimeElapse will NEVER be exactly the same between processing cycles... If you do what I do and always have the TimeElapsed & FPS showing on the screen somewhere you will notice it often flits back and forth between increments of about n to n+15/20 milliseconds... use this to test if time is really running weird in your program or if it is just a variable rounding error.

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08-04-2006, 02:48 AM

RonenNess

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Join Date: Mar 2006

Location: Israel

Posts: 150

arr found the problem.
i forgot to do TimeElapse as public in my moudle and im using that TimeElapse in other classes, so VB just didnt find the variable and created new one with random left-over values in it.

but thanks anyway.

08-04-2006, 12:19 PM

passel

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Posts: 7,714

VB shouldn't create new ones if you use Option Explicit at the top of all your modules.
This helps prevent problems like this.

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08-04-2006, 03:06 PM

Alkatran

Contributor

Join Date: Jun 2003

Posts: 539

Option explicit is a MUST for programming anything decent! There is nothing more annoying than looking for an error only to find out you misspelled "chioce."

As soon as you read this, open VB and:
tools -> options -> turn on "Require Variable Declaration"