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How to fix lag in flightgear

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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How to fix lag in flightgear

Postby theBestgie2007 » Fri Sep 27, 2019 6:15 am

Hi, I have just recently just started playing flight gear. But when I started playing it was laggy when I would move the camera around.

I am currently playing on Windows 10 home.
I use version 2019.1.1.
My graphics card is Intel(R) HD Graphics 520.
It lags at any airplane at any airport.

What should I do

Thanks
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Re: How to fix lag in flightgear

Postby Thorsten » Fri Sep 27, 2019 6:29 am

Get a real graphics card, the Intels are nice for watching movies and similar things, but for really heavy 3d rendering applications like FG they're seriously overworked.
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Re: How to fix lag in flightgear

Postby WoodSTokk » Fri Sep 27, 2019 12:27 pm

I have a nVidia GTX1060 (6MB) and have also lags. If i rotate the view in a direction where i have not looked until now, it lags.
After starting the sim, i rotate the view slowly over 360°. This load all models and scenery around the aircraft.
After that, i have no lags.
I think this comes from loading the scenery and models from the HDD. I think, if we store the data files on a SSD, the lags become very short or will disappear.
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Re: How to fix lag in flightgear

Postby enrogue » Fri Sep 27, 2019 12:33 pm

I use an Intel NUC for mucking about with. It has a Core i5-7300U with HD620 graphics & 8GB ram which is fine for what I do, and does suffer from lag when rotating the view with the mouse at first. I find though, that once I've viewed all around that stops - it may be loading textures causing the issue.

One tweak to make to fix frame rate issues (for me at least) is to select Debug->Cycle GUI Style to change to the gui with antialiased fonts - this has a big effect for me
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Re: How to fix lag in flightgear

Postby Parnikkapore » Fri Sep 27, 2019 12:59 pm

Just to report in, yes, FG lags when you turn views or change to external view too. Turn around once and no longer lags (but took ~6GB of RAM from 7... oof)

[technicalese] I believe it is due to loading new scenery chunks, possibly especially models. From what I've heard, FG is super single-threaded, and I wouldn't be surprised if the loading routines block the main loop and cause it to "freeze"... [/technicalese]
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Re: How to fix lag in flightgear

Postby Thorsten » Fri Sep 27, 2019 1:54 pm

Then for god's sake switch OSG multi-threading in in the config file if that is a bottleneck for you...
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Re: How to fix lag in flightgear

Postby enrogue » Fri Sep 27, 2019 3:12 pm

I always have multithreading turned on - Intel HD graphics still lags a bit.

AMD Vega integrated graphics doesn't seem to have the issue so much, but then again it is quite a bit more powerful than the Intel on the graphics side
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Re: How to fix lag in flightgear

Postby legoboyvdlp » Fri Sep 27, 2019 4:08 pm

It's loading textures that is the problem - switch the DDS cache on (using a binary that has NVTT support - that is an official release, nightly, or a self-compiled binary with NVTT built) and the problem goes away.
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Re: How to fix lag in flightgear

Postby enrogue » Fri Sep 27, 2019 8:06 pm

lego: that will only work in Windows (I realise the poster is on windows but...)

I've compiled NVTT into OSG myself on Linux & it does reduce the lag but there are serious visual artifacts due to varying DDS texture compression support in linux drivers. I have the DDS cache turned on in any case - it works ok without compression

On macos it's a different story - using DDS textures results in shiny black surfaces everywhere (as far as I remember it's the mipmapping that macos doesn't support). I can't even get OSG to compile at all with NVTT support on macOS
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Re: How to fix lag in flightgear

Postby Parnikkapore » Fri Sep 27, 2019 10:58 pm

I didn't realize OSG handles loading too!

I have both OSG multithreading enabled and DDS cache on (daily PPA), and the "loading lag" is now very slight, although still noticeable (~0.5s, compared to ~3s). It seems to be slower when less RAM is available though.
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Re: How to fix lag in flightgear

Postby wkitty42 » Sat Sep 28, 2019 11:25 am

legoboyvdlp wrote in Fri Sep 27, 2019 4:08 pm:It's loading textures that is the problem - switch the DDS cache on (using a binary that has NVTT support - that is an official release, nightly, or a self-compiled binary with NVTT built) and the problem goes away.

FWIW: you don't need NVTT... the texture cache will use it to compress the textures if it is available otherwise they will be cached uncompressed... so mainly NVTT will help save drive space only... i don't have NVTT here and the DDS cache works fine...
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"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: How to fix lag in flightgear

Postby V12 » Sat Sep 28, 2019 8:17 pm

When I turn on DDS texture cache, on my Concorde (and probably not only on this plane) I lost graphics on some objects.

EDIT :
Strange, problem is only with some .png textures. When I one problematic texture converted into .jpg, it was displayed correctly.
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Re: How to fix lag in flightgear

Postby wkitty42 » Sun Sep 29, 2019 2:03 pm

investigation might include studying the failing pngs' format and compare them with working pngs' format...

maybe something like having the alpha channel or not may be involved?
"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: How to fix lag in flightgear

Postby V12 » Sun Sep 29, 2019 5:31 pm

Thank You for advice. Problematic .pngs was not in RGB, but only in grayscale.
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