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Jittery

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Jittery

Postby Praxxus » Fri May 25, 2018 8:21 pm

I find the simulation gets very jittery/jumpy at or above 110 Fps, the only other option is to limit FG to 70Hz which I find a little inflexible wise. Is there going to be some sort of update to accommodate faster GFX cards/setups ?
I appeciate you can delve into GFX card driver settings etc. Especially nVidia settings wise. Anyone wanna call a solution out ?

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Re: Jittery

Postby legoboyvdlp » Fri May 25, 2018 8:50 pm

The FDM runs at 120HZ as far as I remember. I am wondering if the graphics are updating faster than the FDM and causing this?
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Re: Jittery

Postby Praxxus » Fri May 25, 2018 9:02 pm

That is the general point I would be making....

Is there anything that can be done to Fg to open up faster fps without upsetting the fdm refresh rate ?

iirc the old launcher could be tuned fdm refresh rate wise ? On a 2:1 ratio would be ok ie 2 fdm to 1 fps ? or viceversa ?

I'm probably wishing for Unicorns but it might be something to consider for a future release as people upgrade to much faster machines....

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Re: Jittery

Postby lomar » Fri May 25, 2018 9:21 pm

i'm pretty sure it's possible to change the FDM frequency, i just don't know where is this function(i've seen it in the old launcher but it's gone in the new one)
try playing with the command line perhaps and see if you discover something
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Re: Jittery

Postby Praxxus » Fri May 25, 2018 9:24 pm

Hasn't someone put out a *user friendly* new launcher ?
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Re: Jittery

Postby lomar » Fri May 25, 2018 11:04 pm

Praxxus wrote in Fri May 25, 2018 9:24 pm:Hasn't someone put out a *user friendly* new launcher ?


The new launcher is more "user friendly" and a bit more good looking but it lacks a lot of advanced features of the old FGRun
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Re: Jittery

Postby PINTO » Sat May 26, 2018 1:02 am

In the advanced options, use --model-hz=n where n is the hertz you want the FDM to run at. JSBSim is default at 120. Be warned that this could break some planes.

edit: for all command line options available see http://wiki.flightgear.org/Command_line_options
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Re: Jittery

Postby Praxxus » Sat May 26, 2018 1:48 pm

Thanks PINTO - I broke the first rule of posting queries I'm afraid !

I did'nt look in the WIKI first :( Stoopid me....

I see that you can run the FDM n times faster with --speed=n. So will give it some experimentation...

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Re: Jittery

Postby wkitty42 » Sat May 26, 2018 5:05 pm

i don't understand why folks want to run their FPS faster than the human eye can see... ~30fps is all the human eye can see and register changes... anything more is just pure overkill for overkill's sake...
"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: Jittery

Postby Thorsten » Sat May 26, 2018 5:27 pm

Well, yeah - and I don't think too many monitors do more than 60 Hz.

So it actually makes sense to throttle framerate to 60 (or 70) Hz...
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Re: Jittery

Postby wkitty42 » Sat May 26, 2018 5:30 pm

yeah, that's my thoughts, too... however, i do see quite a few ""gamer"" monitors touting 144Hz as their refresh rate... in some ways, it kinda makes me think of the marketeers that got folks to buy "pet rocks" ;)
Last edited by wkitty42 on Sun May 27, 2018 9:30 am, edited 1 time in total.
"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: Jittery

Postby Praxxus » Sat May 26, 2018 7:53 pm

Oh yeah, Sorry, my monitor is 144Hz but i got it running at 120Hz.

Should've mentioned that as well. My bad.

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Re: Jittery

Postby Thorsten » Mon May 28, 2018 5:12 pm

Hm, I guess your eyes still only update at around 30 Hz, so the monitor seems a marketing gag (unless you're an insect of course, their eyes can see much faster rates).

Bottomline - throttle at 60 Hz, that's comfortably above what you can see, there's no point in the rest.
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Re: Jittery

Postby PINTO » Mon May 28, 2018 8:14 pm

The eyes-can-only-see-30Hz thing is largely believed to be a myth. The USAF studied this by flashing a picture of an aircraft for 1/220th if a second - participants were able to ID the plane repeatedly and reliably.

Heres a gif with text scrolling at 15FPS, 30FPS, and 60FPS. There is a plain difference between all three.
Image
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Re: Jittery

Postby WoodSTokk » Mon May 28, 2018 8:18 pm

wkitty42 wrote in Sat May 26, 2018 5:05 pm:i don't understand why folks want to run their FPS faster than the human eye can see... ~30fps is all the human eye can see and register changes... anything more is just pure overkill for overkill's sake...

This comes from the old shooter games. The calculation of the physics in the old game engines was made every frame.
This means, if you jump, the ballistic curve was only calculated at the same rate as frames will be shown. If a player jump, he/she reach the maximum high only if the calculation will be done exactly at the moment where the ballistic curve is on top.
As example the IDtech3 engine (Quake3Arena, Return to Castle Wolfenstein, Enemy Territory, etc..) reach the top of the curve with 43, 76, 125 and 333 (maximum) FPS. So the most player configured there game for a constant frame rate one of the above values.
I think there are many gamer they dont know the relation between physics and framerate in the old engines, so they only say: "higher framerate is better".
But in FG (as well as in other newer games and simulators), the physic (FDM) and framerate isn't bounded.
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