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Lag/Stuttering while flying

Graphics issues like: bad framerates, weird colors, OpenGL errors etc. Bad graphics ar usually the result of bad graphics cards or drivers.
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In order to help you, we need to know a lot of information. Make sure to include answers to at least the following questions in your initial post.

- what OS (Windows Xp/Vista, Mac etc.) are you running?
- what FlightGear version do you use?
- what graphics card do you have?
- does the problem occur with any aircraft, at any airport?
- is there any output printed to the console (black window)?
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Re: Lag/Stuttering while flying

Postby kbecker » Wed May 04, 2011 1:03 pm

I'm still somewhat new to FlightGear. Is there a way to script a 360 degree view rotation and run it at startup, so I don't have to manually do it?
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Re: Lag/Stuttering while flying

Postby clrCoda » Fri Jun 24, 2011 2:34 am

I noticed from your posting of your .fgsrc file that you have the maximum sim loop rate set to 0.01. This can, at least for me, reduce my frame rate dramatically.

I suppose you have tried higher settings? Depending on the plane, I set anywhere between 1.0 and 0.1 . This is something that you can adjust while the sim is running, for testing.

With sim running, open the properties browser, browse down to 'sim' and select it, then about five or six pages down you will find the property, which you can adjust in real time and re-set for testing.

Good luck! hope it helps
Ray
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Re: Lag/Stuttering while flying

Postby clint » Sun Jul 24, 2011 1:48 am

I am encountering the same problem.
And it also does not seem to be an OS issue as I am running Windows Vista on this machine.
It is equipped with an ATI Radeon card.
I know, that those cards produced some other errors. But I don´t think they have got to do with the "hickups" (normally followed by periods of extreme drop in framerates).
I have allready fiddled with a number of properties which I thought could help in this context, but nothing helped so far.
(To be honest: I managed to turn off the runway lighting and could not turn it on again so far, but that is another problem. I fly a lot in daylight now :D )
My guess is, that the hickups have something to do with the weather system. Changing settings there increase or decrease the occurences of stutters most in my case.

I hope, this can be solved soon,
clint
Happy landings? I had a few...

All the best and many happy landings from clint.
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Re: Lag/Stuttering while flying

Postby Marius » Thu Aug 25, 2011 4:33 pm

I also have this problem, but with FG 2.4.0 on Windows 7. I am also under the impression that it is somehow related to camera movements. When I'm flying straight and level the stuttering is there, but only minimal. But when I start to fly tight turns, FG becomes impossible to play. The intervals between those lags are then shorter and also the time the simulation pauses is a lot longer (up to 1 or 2 seconds long). A look into the Process Explorer shows that during those pauses the CPU usage of FG drops from around 60% to 0% and I cannot see any other activity, so from that point of view I don't see any reason why this is happening.

Here some details about my system:
CPU: Intel Core 2 Duo E8400 3.0 GHz
RAM: 8 GB DDR2-SDRAM
Graphics Card: XFX ATI Radeon 5870, 1 GB DDR5 RAM
OS: Windows 7 Home Premium
FG: 2.4.0

FG 2.0.0 works without any problems though, so I'm afraid for now I'll have to stick with this version.
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Re: Lag/Stuttering while flying

Postby dany93 » Fri Aug 26, 2011 10:54 pm

Marius wrote:When I'm flying straight and level the stuttering is there, but only minimal. But when I start to fly tight turns, FG becomes impossible to play. The intervals between those lags are then shorter and also the time the simulation pauses is a lot longer (up to 1 or 2 seconds long).
My explanation is that when you fly straight, FG is 'prepared' to display the landscape coming. When you turn, FG has to load chunks of landscape it's not prepared to.
A look into the Process Explorer shows that during those pauses the CPU usage of FG drops from around 60% to 0% and I cannot see any other activity, so from that point of view I don't see any reason why this is happening.

I think that's the Graphics Card which is saturated, or being loading; not the CPU. Although I wonder how it can happen with yours (1 GB memory is usually considered as perfect). Updated?
You can read your Graphics Card activity by your ATI Catalyst Control Center > Advanced > Graphics > ATI Overdrive (although I can have brief image freezes or 10 fps on some scenes, like in Paris region, with 20 - 50% activity; memory loading?).
Anyway, I've read this several times. FG 2.4.0 seems very demanding (I still have only FG 2.0.0). That's a pity if you have to uncheck the options...
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Re: Lag/Stuttering while flying

Postby clint » Sun Aug 28, 2011 2:06 am

I have another idea:
The graphic cards are very sensible to heat.
If Your PC or Laptop is about one year old and You never took it apart to clean the ventilation grill and fan(s),
then this could be part of the problem.
I increased framerates by 30% just cleaning the thing.
BUT BE AWARE: Some PCs/Laptops are easy to clean, some are NOT!!!!!
If You are not sure to perform the task, leave it to Your trusted computer dealer!!!!!
(e.g.: it takes about 20 minutes to clean the ventilation grill of an ASUS laptop, but more than two hours to do the same with an HP...)
Happy landings? I had a few...

All the best and many happy landings from clint.
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Re: Lag/Stuttering while flying

Postby clrCoda » Sun Aug 28, 2011 2:14 am

I had spent much of the last two weeks touring all over Canada with out any lag issues in several of the simulators.

As soon as I started flying Europe, yesterday, the lag has been very bad, and for a time yesterday the network bandwidth I was receiving as I approached and departed EDDF was 100 times normal, and got better or improved I should say the further I got away from EDDF, but the frame lag has been terrible this entire time in norther Europe and England.

I'm assuming that there is a some issue with the scenery and the newer 2.4's as I have this problem of lag with the 2.4rc4

Ray
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Re: Lag/Stuttering while flying

Postby Marius » Mon Aug 29, 2011 6:27 pm

Thanks for the ideas, guys! :)

I observed the load on the graphics card and the GPU load was around 20% all of the time, except for the time of a lag, then it dropped to 0%, like the CPU. The ATI control center showed a temperature of around 70°C, which is quite low for this card (it's around 65°C on the Windows desktop), and the fan speed was at 48% all of the time (it's 45% on the Windows desktop). So it does not seem to be a performance issue at all. Btw., I'm using Catalyst 11.6.

The ventilation doesn't seem to be a problem. All fans are working and are quite clean as is the CPU heat sink.

I also tried flying in the USA instead of Europe. I picked Chicago Meigs (KCGX), but I've got exactly the same problem there.

I also made the experience that I don't have lags when all I see is water. Also the lags are really related to the camera, because even when the plane is flying straight and I switch to the fly by camera, when the plane closes to the camera and it starts to pan, the simulation pauses for a few seconds.

@clrCoda: Can you tell me a few airports that worked for you? I'd like to try, just to be sure.
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Re: Lag/Stuttering while flying

Postby clrCoda » Tue Aug 30, 2011 3:06 am

Marius wrote in Mon Aug 29, 2011 6:27 pm:Thanks for the ideas, guys! :)

@clrCoda: Can you tell me a few airports that worked for you? I'd like to try, just to be sure.


CYVR is fairly good. CYYQ in Churchill is very good. CYYC Calgary is good as well as CYWG Winnipeg.

Hope this helps you to find some airports to give you a base of statistics to work with,
Ray
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Re: Lag/Stuttering while flying

Postby Marius » Sat Sep 03, 2011 6:45 pm

I tried all those airports and I got the same effect with all of them. I also tried different aircraft models to be sure it's not a problem related to a model.

Of course I tried virtually all the switches I could find and tried turning off everything, but I couldn't find anything that would make this effect go away. :(

So it looks like it'll still be FG 2.0.0 for me.
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Re: Lag/Stuttering while flying

Postby tomw » Mon Sep 05, 2011 5:31 am

Hi!

I had problems similar to those already described. I have the AMD/ATI HD 6800 series card on my system running Windows 7 Pro.

I just bought my computer and immediately experienced major stuttering and hesitations when running V2.4 (2.0 was OK). I tried updating the video card drivers through Windows and was told I had the latest version. I figured I'd be stuck with FlightGear 2.0 as well.

While poking-around the ATI web site I found an update utility for my card that would auto-sense my hardware and download the supporting drivers. So I tried it, and it worked! It replaced original factory CD drivers installed with my system, and eliminated almost 99% of my stuttering. I could finally use version 2.4.

Here's the link: http://support.amd.com/us/gpudownload/Pages/index.aspx
(look for "Automatically Detect and and Install" on the upper-right side of the screen)

I still get some stuttering and hesitation, but it happens so little now that I ignore it.

The only strange thing I get (it happened twice this month) was a complete crash of the video card. It goes to solid black with some audio noise ... but the computer keeps running! I haven't found a quick recovery method yet - so I'm forced to perform a manual power-down of my system. This only happened twice in the last 30 days, but I have some concerns.

I hope this helps someone....

~Tom

-------------
Note: since I bought my computer a few days prior to trying this, I performed a full hard drive image backup as well as set a restore point. I wasn't sure what this update was going to change/destroy, so I took some extra precautions. I highly recommend you do the same before trying this. :)
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Re: Lag/Stuttering while flying

Postby dany93 » Mon Sep 05, 2011 11:35 am

Hi Tom,

And welcome to the FlightGear forum.

Kind of you giving all these explanations, sure they will be useful to others. Thanks.
I confirm your experience for checking the video card version from Windows or built-in ATI Catalyst Control Center: probably because the version is an OEM one, checking gives a wrong message (if it only works...). The only way is (ATI Radeon) AMD website, check, and probably uninstall the OEM version to replace it by the AMD last version (or a previous one if the last one is flawed or FG doesn't work with it).

Cheers,

Dany
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Re: Lag/Stuttering while flying

Postby Marius » Tue Sep 06, 2011 4:38 pm

I updated my video drivers from 11.6 to 11.8 and that did the trick. The stuttering is gone completely. :) I wouldn't have thought that a minor version update in a video driver would fix this effect. It's really kind of embarrassing that I did not try that before. :oops:

However, now I've got this problem. :roll: But at least FG 2.4.0 is now playable. :)
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Re: Lag/Stuttering while flying

Postby nicegood » Wed Sep 07, 2011 4:49 am

I have tested your case,I download the ati 5870 driver ,install the fg 2.4.0 and still met the same problems:stutter(the large terrain:the ive format),why? please tell me how to load the format "ive"(using the vpb) in the tilemanager?
thanks
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Re: Lag/Stuttering while flying

Postby wrostek » Tue Feb 28, 2012 8:23 pm

Hi all,

I'm as well struggling with stutter for some time now.
I was hoping that FG2.6/OSG3.0 would improve the situation
but I still see serious stutter.

Months ago I started with FG2.0.0/OSG2.8.2 on Suse Linux
with ATI graphics. I had stutter of various degree. Digging
down I found at least two different sources. A stutter of
far more than 1 sec I could track down by OSG trace to see
it related to tile loading. This one is easier to address.

For the other type I setup a 20min reproducable circle.
In OSG I spawned a watchdog thread to raise a core if not
retriggered within 200msec.

Even if limited on OSG level the ATI fglrx driver spawns
multiple threads. Looking at the coredump it seems to me
that one of the driver threads is awaiting a timed call
for a futex. This matches my observation that this stutter
is very accurate about 1 second. I didn't see that OSG
is doing any work at that time.

On a second machine with NVidia card the situation is far
better. But even here I encounter stutter of about 100-300msec
within the same scenario.

Looking at some high-end YouTube videos I saw stutter several
times. I'm not an expert in debugging at that level . But may
be this info is of any help.
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