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problem with scenery appearing and disappearing...

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problem with scenery appearing and disappearing...

Postby trulyone » Thu Jul 30, 2009 6:12 pm

Hello Everybody,

I am having a strange problem with the scenery. Flightgear only shows scenery within a few miles of where I am at any one time.
This is not a scenery installation problem, as it happens with default scenery as well as that which I have installed manually.

These screenshots should illustrate the problem:

fgfs-screen-003.jpg

fgfs-screen-002.jpg

fgfs-screen-001.jpg


When I am above an area the scenery appears, but all around my location there is nothing, not even ocean. As I approach an area, the scenery appears ahead of me, and disappears behind me. It is noticable as low as 3000ft, these shots were taken at 40,000ft.

In these pictures I have disabled clouds, fog and skyblend for clarity but it happens in all situations.

I am running fgfs under debian lenny, amd64 and a fairly old ATI x200 card on a dell laptop. I have no other
running problems, it runs quite smooth and I can fly with no problems using navaids etc etc.

I have 2 versions of flightgear, the first is the default one thatt comes with lenny, which is 1.0.0 i think, and I downloaded CVS a couple weeks ago: both versions have the same problem.

Things I have tried which make no difference:
- changing weather settings
- changing aircraft
- changing visibility
- changing LOD settings
- changing scenery areas

I have trawled the web, but havnt seen any solutions to this.
Has anyone had the same problem? If so, please let me know if you were able to fix it, and how :)

thanks..
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Re: problem with scenery appearing and disappearing...

Postby MAKG » Thu Jul 30, 2009 8:07 pm

That seems to be just the way scenery works in FG. The last thing you want to do is render an infinite image, as that takes infinite time.

There are other strategies (for instance, decimation based upon distance with tiling limitations based upon horizon distance), but the one chosen here is local tiling. It works fine in decent visibility, but it has problems when the visibility is outstanding, even if the weather isn't turned off. The advantage to the approach taken is that it has strong limits on computational expense.

Said another way, it's a feature, not a bug. Given the simple algorithm, there may or may not be a tunable distance, but computational expense grows FAST with distance (number of vertices should grow as the cube of distance in the absence of decimation).
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Re: problem with scenery appearing and disappearing...

Postby cubeist » Fri Jul 31, 2009 6:53 pm

What you need to do is turn fog back on. Since FG is a sim, not a game, I believe the developers created fog to simulate what it really looks like while flying; and of course to ease the amount of work your computer has to do to render. (I would guess that with your current settings you get low frame rates unless you have a supercomputer).

When flying in the real world there is naturally moisture in the air, which from elevation obscures the ground. So, if you turn fog back on, you can still set your view distance at a long, long way, and get great views while maintaining the sim aspect.
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Re: problem with scenery appearing and disappearing...

Postby MAKG » Fri Jul 31, 2009 7:57 pm

There are some instances where the defaults do not yield correct scenes, even with fog.

I've made a number of light-plane flights around the Rockies and eastern Sierra Nevada, only to have a huge mountain range suddenly appear in my path on a clear day. It makes pilotage very difficult when your landmarks aren't there.

Is there a tunable rendering distance I can turn up?
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Re: problem with scenery appearing and disappearing...

Postby VicMar » Sat Aug 01, 2009 7:12 am

Hi,
I don't know if this is the answer, but it is the first thing I would try adjusting.
Picture 2.png

This is at the bottom-right of the Mac Launcher 'features' page (showing the default setting). I can't tell you where to find it in other OSs, but I hope that helps.

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Re: problem with scenery appearing and disappearing...

Postby cubeist » Sun Aug 02, 2009 6:30 pm

You can change the visibility from inside the environment panel if you are not using 'real-weather-fetch'. You can also adjust visibility meters by pressing x/X, but you must have fog turned on.
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Re: problem with scenery appearing and disappearing...

Postby VicMar » Sun Aug 02, 2009 8:39 pm

You can also adjust visibility meters by pressing x/X, but you must have fog turned on.

x/X Zooms in and out on a Mac. Unless it is totally different in other OS , this is something completely different.
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Re: problem with scenery appearing and disappearing...

Postby AndersG » Sun Aug 02, 2009 8:42 pm

VicMar wrote:
You can also adjust visibility meters by pressing x/X, but you must have fog turned on.

x/X Zooms in and out on a Mac. Unless it is totally different in other OS , this is something completely different.
Vic


To change visibility you use z/Z, but, as has already been said, if you use real weather fetch that will (slowly) override your manual adjustments.

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Re: problem with scenery appearing and disappearing...

Postby MAKG » Mon Aug 03, 2009 4:12 pm

You guys are missing the point.

Adjusting the transparency of fog does not affect how far the terrain is rendered. It just affects how saturated it is. This has nothing to do with "real weather fetch."

It doesn't affect the point that 100+ mile visibility on a good day is a fact of life in the West, and hiding that with fog-colored glasses doesn't aid the simulation goal of this software. What it needs is to turn up the tiling distance to be greater than the fog optical depth. Whether that's manual or automatic is an exercise for the reader. Though it's clearly very easy to overdo and whack up the rendering speed. But that's a tradeoff for the operator to make.
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Re: problem with scenery appearing and disappearing...

Postby cubeist » Mon Aug 03, 2009 5:43 pm

MAKG wrote:You guys are missing the point.

Adjusting the transparency of fog does not affect how far the terrain is rendered. It just affects how saturated it is. This has nothing to do with "real weather fetch."

It doesn't affect the point that 100+ mile visibility on a good day is a fact of life in the West, and hiding that with fog-colored glasses doesn't aid the simulation goal of this software. What it needs is to turn up the tiling distance to be greater than the fog optical depth. Whether that's manual or automatic is an exercise for the reader. Though it's clearly very easy to overdo and whack up the rendering speed. But that's a tradeoff for the operator to make.


Your right, only a certain amount of scenery is rendered. I would guess this has evolved to spare framerates on the majority of users computers, but perhaps has not evolved enough as hardware abilities (ie graphic cards) can now render an enormous amount of detail.

However, as it stands now, if you put your visibility up to around 80 - 100 km (which I believe is the furthest you can see from altitude before the curvature of the earth starts blending the horizon and obfuscating details), I think it looks pretty close to realistic. I think what you are forgetting, is that even on the clearest, calmest of days with max visibility, you actually only see clear details below you and perhaps as far away as 20 or 30km... then the ground starts to fade due to moisture/particles in the air.

I would agree that we need a bit more distance for rendering, but to see clear detail at 100 miles... that's not realistic anymore, that's an arcade game.
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Re: problem with scenery appearing and disappearing...

Postby MAKG » Mon Aug 03, 2009 8:17 pm

Clear detail at 100 miles is not physical.

SOME detail at 100 miles is. Especially, large mountain ranges. I've personally seen Mt. Shasta from north of Sacramento, from the ground. Not very clearly, but you could tell it was there. That's more than 100 miles.

The geometric horizon at 35,000 feet is almost 250 miles away.
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Re: problem with scenery appearing and disappearing...

Postby Andrew Kennedy » Sun Apr 19, 2020 4:43 pm

I have a similar problem but I can't find out a way to fix it. My plane is stuck in water. This happens with the default scenery.
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Re: problem with scenery appearing and disappearing...

Postby stuart » Sun Apr 19, 2020 6:35 pm

Andrew - what version are you using?

MAKG - you can control the range at which scenery is _loaded_ using the View->Adjust LOD Ranged dialog. The "Bare" slider controls the range at which scenery is loaded. Try increasing that.

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Re: problem with scenery appearing and disappearing...

Postby Johan G » Sun Apr 19, 2020 6:43 pm

Andrew Kennedy wrote in Sun Apr 19, 2020 4:43 pm:My plane is stuck in water. This happens with the default scenery.

If you are starting from an airport outside of the default scenery it will take FlightGear a little time to download the TerraSync scenery that it will need to show you scenery in paces new to you FlightGear installation.

There are at least two ways to get around that. 1) You can start FlightGear at your desired airport and let it run while you do other things (make sure you enable TerraSync), or 2) use a scenery manager like for example TerraMaster.
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Re: problem with scenery appearing and disappearing...

Postby wlbragg » Sun Apr 19, 2020 6:49 pm

If your starting in water, that is because you have no scenery installed at that location. If you install FG for the first time and try to start anywhere other than Hawaii or the default airport of the release (if there is one) and you have not turned on terrasync, then you will start up in water. FG is delivered with only a small amount of scenery. Turn on automatic scenery download and you should start seeing scenery anywhere you go. Beware it can take a while to load at times.
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