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Lag Spiking in Flightgear

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Lag Spiking in Flightgear

Postby reece0306 » Sun Oct 18, 2020 5:21 pm

I am having an issue with my Flightgear when you move around the cockpit, the frame rate drops. I am running Windows 10 64bit. I was using 2018.3.6 Flightgear version, my graphics card is an NVIDIA GeForce 930M with Intel HD Graphics 5500. Is there any way to fix this? My graphics settings are already at the lowest in the sim.
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Re: Lag Spiking in Flightgear

Postby wkitty42 » Sun Oct 18, 2020 5:28 pm

which craft? some are quite detailed and do consume FPS at times...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Lag Spiking in Flightgear

Postby legoboyvdlp » Sun Oct 18, 2020 6:30 pm

Make sure you are in fact using the Nividia, not the Intel graphics card.
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Re: Lag Spiking in Flightgear

Postby reece0306 » Mon Oct 19, 2020 5:01 am

I was setting FlightGear to use NVIDIA Graphics.
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Re: Lag Spiking in Flightgear

Postby Parnikkapore » Mon Oct 19, 2020 11:13 pm

I'm on Intel graphics, but I have similar lag spikes when turning around too. You can reproduce by turning the camera around once right after opening the simulator.

Subsequent camera turns don't result in lag though, so maybe the lag is caused by the scenery loading process?
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Re: Lag Spiking in Flightgear

Postby wkitty42 » Mon Oct 19, 2020 11:50 pm

yes, this ^^^^^

i generally wait several minutes when i load FG before i start doing much of anything... especially if i have AI enabled... loading 200000+ flights takes a while... at some point, i generally switch views and look around... then i go back to my standard view and start my workflow in my craft...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Lag Spiking in Flightgear

Postby Johan G » Tue Oct 20, 2020 12:16 am

wkitty42 wrote in Mon Oct 19, 2020 11:50 pm:a[...] at some point, i generally switch views and look around... then i go back to my standard view and start my workflow in my craft...

That is a tip I have seen now and then over the years.

Another tip I have seen to remove some lag spikes is to throttle the fps in the rendering options dialog.
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Re: Lag Spiking in Flightgear

Postby wkitty42 » Tue Oct 20, 2020 1:00 pm

throttling the FPS to the vertical sync is possible and valid if your GPU achieves 60 FPS to start with... if it cannot, throttling won't do any good at all ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Lag Spiking in Flightgear

Postby Johan G » Tue Oct 20, 2020 4:41 pm

What it throttling at say 25 or even 15 fps?
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Re: Lag Spiking in Flightgear

Postby wkitty42 » Tue Oct 20, 2020 5:24 pm

i'm only aware of throttling to vertical sync... not sure i've seen actual numbers being given...

so if a monitor's vertical sync is at 60Hz, 60FPS is max... if the vsync is 70Hz, then 70FPS is the max...

i think i got that right... today's monitors are a little different than the CRTs of yesteryear...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Lag Spiking in Flightgear

Postby Parnikkapore » Tue Oct 20, 2020 11:18 pm

My "startup routine" is to turn around in cockpit view, go to helicopter view, turn around there, then go back to cockpit view.
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Re: Lag Spiking in Flightgear

Postby V12 » Wed Oct 21, 2020 3:08 am

I looked around in the cockpit, in my case that helped much.
There is not very well documented trick with OSG parameter OSG_NUM_DATABASE_THREADS, specialy on modern 4 and more core CPU. In windows use this environmental parameter with
SET OSG_NUM_DATABASE_THREADS=X
on Linux
EXPORT OSG_NUM_DATABASE_THREADS=X
where X is thread count. I tested with X between 2 and 16, best result for my 8 core CPU was 6. It removed almost all stuttering on scenery load.
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Re: Lag Spiking in Flightgear

Postby Husky Dynamics » Thu Oct 22, 2020 5:47 am

^^ Details on how to do this?

Also, I typically look around in the cockpit first, then swap to helicopter or model view and do a 360 degree pan, then toggle through all the other views (some of which lag quite a bit themselves, *cough cough* 707 engineering panel)
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Re: Lag Spiking in Flightgear

Postby V12 » Thu Oct 22, 2020 6:57 am

Set environment variable. That is all.
In windows - right mouse on This computer, Properties, Advanced properties (I'm not sure, I have not EN Win), then click on Environment variables, add new OSG_NUM_DATABASE_THREADS
In Linux I tested it from console :
EXPORT OSG_NUM_DATABASE_THREADS=X
fgfs --launcher
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Re: Lag Spiking in Flightgear

Postby wkitty42 » Thu Oct 22, 2020 2:36 pm

you really only need to set it in the one session running FG, not the entire system ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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