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Flightgear very slow to look left and right

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Flightgear very slow to look left and right

Postby mahela007 » Wed Feb 26, 2020 12:53 pm

Hi guys.
I recently installed flightgear on an AMD Ryzgen 3400G based PC.
I get good frame rates exceeding 50 (sometimes even with high graphics settings) and the game is by and large playable.
However, just after loading up, panning the view left / right and up / down causes the game to temporarily freeze for a few seconds. Then it resumes working until I pan further.
It then freezes again for a few seconds and then resumes. Moving the view around in the areas I have already panned to doesn't cause any freezes. It seems like FG is taking time to load up new scenery (or something else which depends on the view direction) into RAM because once I do this process several times and ''cover" the entire 360 degree field of view, the sim works smoothly. This whole process takes several minutes every time I start up the game and I'd really love to fix it so that I can use FG..

(If it's relevant, the spalsh screen looks very glitchy with bad colours and pixels while FG is loading up... however, since this doesn't seem to be causing any functional problems, I can deal with it. )
Thanks for any help!
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Re: Flightgear very slow to look left and right

Postby wkitty42 » Wed Feb 26, 2020 1:32 pm

yes, this sounds like the engine loading the scenery objects for the area you are headed to... it is normal as you don't need to load those objects if you're not going to look at them, right? ;)
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Re: Flightgear very slow to look left and right

Postby Hooray » Wed Feb 26, 2020 1:43 pm

as has been said, there is the equivalent of a scenery/tile cache that is populated "on demand" - admittedly, this is somewhat conservative apparently, but changing the defaults would also change memory occupancy accordingly.

Depending on how much RAM you have, you could tweak fgfs to pre-load such tiles and/or simply move them to a RAM disk (or SSD) to speed up loading from disk, I'd guess you will at least want to have 6-8 gb of dedicated RAM and at least 2gb of VRAM to tinker with those options.
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Re: Flightgear very slow to look left and right

Postby mahela007 » Thu Feb 27, 2020 5:33 am

wkitty42 wrote in Wed Feb 26, 2020 1:32 pm:yes, this sounds like the engine loading the scenery objects for the area you are headed to... it is normal as you don't need to load those objects if you're not going to look at them, right? ;)


Just to clarify, it doesn't happen when I'm actually moving the aircraft to a new area .. just when I'm looking left it right.

@Hooray I have 16GB if RAM of which about 2 is used for the VRAM. I think I should be able to tweak the settings you mentioned. Where can I find them?
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Re: Flightgear very slow to look left and right

Postby Thorsten » Thu Feb 27, 2020 7:26 am

I suspect it might rather be the GPU getting a new batch of objects into video ram - I believe we should all be able to force such behavior by increasing vegetation density to pretty large values. The bottleneck then is not rendering the millions of trees, but getting them in and out of memory as the view pans.

I can force that on a GeForce 1080, so I assume it can be forced on pretty much any architecture.
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Re: Flightgear very slow to look left and right

Postby Hooray » Thu Feb 27, 2020 8:54 am

mahela007 wrote in Thu Feb 27, 2020 5:33 am:Just to clarify, it doesn't happen when I'm actually moving the aircraft to a new area .. just when I'm looking left it right.

given that, Thorsten's theory sounds much more plausible and workable - also, he's much more familiar with the GPU/graphics side of things, so he's much more likely to be right here ;-)

Personally, I am not sure how to come up with a test case to tell what exactly is going on here, maybe Thorsten has an idea ?

But given your specs (AMD Ryzen 3400G, quad core, 16 gbRAM/2gb VRAM), I suppose the machine is doing a good job actually - based on googling your specs, it seems the setup is commonly described as a "multimedia/office system" and that it used an integrated GPU with shared RAM, is that right ?

If in doubt, please do share some more info with us - but my impression is that you are getting pretty good performance, and that the issue you describe might be related to the fact that you are dealing with an integrated graphics card, rather than a dedicated one that has its own VRAM, again it's just a guess -Thorsten would be in a much better position to come up with heuristics to tell what is going on here.

As far as I can tell, the GPU is called "AMD Radeon Vega 11": https://www.notebookcheck.net/AMD-Radeo ... 628.0.html

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Re: Flightgear very slow to look left and right

Postby V12 » Thu Feb 27, 2020 11:31 am

mahela007 wrote in Wed Feb 26, 2020 12:53 pm:(If it's relevant, the spalsh screen looks very glitchy with bad colours and pixels while FG is loading up...

Again AMD GPU driver related problem. Try install other GPU driver.
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Re: Flightgear very slow to look left and right

Postby xcvb » Thu Feb 27, 2020 11:55 am

I have the Ryzen 5 2400GE in my HTPC and the performance in FlightGear is very good. You must note that the Ryzen 5 3400G is quite new and you will need a very new distribution (Linux Mint 18 should not work).
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Re: Flightgear very slow to look left and right

Postby Hooray » Thu Feb 27, 2020 12:04 pm

that's good to hear, you might want to post your kernel/driver details here, or at least show the output from running glxinfo and/or a screen shot showing the help/about dialog
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Re: Flightgear very slow to look left and right

Postby mahela007 » Thu Feb 27, 2020 5:40 pm

Hooray wrote in Thu Feb 27, 2020 12:04 pm:that's good to hear, you might want to post your kernel/driver details here, or at least show the output from running glxinfo and/or a screen shot showing the help/about dialog


Sorry.. my mistake. Although my account says I'm on linux mint, I'm actually running FG on windows 10 (bought a new PC. ;) My Old FG installation was on linux ) . What are the windows equivalents of those commands?

Also, I think this is unlikely to be to due to me using an APU (and thus not having enough GPU power) because I've run flightgear without any issues at all on a much older and much lower speced system.
I play Dirt Rally 2.0 with the my Ryzen system and I get reasonably good frame rates.. usually above 50.
I'd love to provide any more info for you to better analyze the problem.. :) Please let met know how to do so..
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Re: Flightgear very slow to look left and right

Postby mahela007 » Thu Feb 27, 2020 5:56 pm

I also noticed just now that the "view-freezing" also happens when I"m looking around inside the cockpit with no part of the external environment visible. (like looking around at the floor for example)
Doesn't this make it less likely that the issue is caused by environmental objects like trees?
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Re: Flightgear very slow to look left and right

Postby wlbragg » Thu Feb 27, 2020 6:44 pm

Depending on how much RAM you have, you could tweak fgfs to pre-load such tiles

The J3Cub has an option in the UI to "Preload Resources". When left selected on exit, the next time you startup it will cache the views and thus avoid that initial delay. However, It takes more time to load the aircraft initially.
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Re: Flightgear very slow to look left and right

Postby mahela007 » Thu Feb 27, 2020 6:48 pm

Thanks but I'm looking for a more general fix..not just for one particular aircraft
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Re: Flightgear very slow to look left and right

Postby wlbragg » Thu Feb 27, 2020 7:44 pm

That aircraft has a fix that can be extended to any aircraft. It will show you how you can do it in nasal if so desired. But it is not elegant by any stretch.
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Re: Flightgear very slow to look left and right

Postby Richard » Fri Feb 28, 2020 11:14 am

wlbragg wrote in Thu Feb 27, 2020 6:44 pm:
Depending on how much RAM you have, you could tweak fgfs to pre-load such tiles

The J3Cub has an option in the UI to "Preload Resources". When left selected on exit, the next time you startup it will cache the views and thus avoid that initial delay. However, It takes more time to load the aircraft initially.


This is probably the time taken to load the textures - as when not using DDS textures the mipmaps have to be generated on the fly and this takes a lot of time on my system (Windows).

On 2019.x there is an option that I called "Use disk space for faster loading (DDS Texture Cache)" on the view->rendering menu that will dynamically create DDS textures and should improve performance - but may also have side effects

For the record preloading isn't something that I'm happy about because it is a hacky solution to a core problem.
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