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Thermal spawning, ridge wind and weather configuration

Everything related to weather simulation, visuals should be discussed in the shader subforum.

Re: Thermal spawning, ridge wind and weather configuration

Postby Ysop » Sat May 15, 2021 4:55 pm

Thanks Thorsten, that was really helpful in a number of ways!
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Re: Thermal spawning, ridge wind and weather configuration

Postby benih » Sat May 15, 2021 6:09 pm

Yes indeeed!
So understood correctly, for me (absolute beginner) i would tune turbulences down to 0 and so can expect the thermals, but without the shaking?

The GUI is good to adjust; it’s just that i had no idea „what“ to dial in. We need this explanation on the soaring wiki entry :)
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Re: Thermal spawning, ridge wind and weather configuration

Postby benih » Sat May 15, 2021 6:10 pm

@Ysop and DECHO: could the inertia be the reason it’s so easy to overtake the tow plane with the ask21-jsbim?
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Re: Thermal spawning, ridge wind and weather configuration

Postby Ysop » Sat May 15, 2021 6:31 pm

@Ysop and DECHO: could the inertia be the reason it’s so easy to overtake the tow plane with the ask21-jsbim?


Could be a consequence of being off course, when the stored energy from the rope propels you forward.
Maybe different matter to be looked at (no forces transmitted if distance smaller than rope length?).

Or just an indication of the aerodynamic "quality" of a motorplane ;-)
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Re: Thermal spawning, ridge wind and weather configuration

Postby S&J » Sat May 15, 2021 6:50 pm

So advanced weather is correct for neither jsbsim or yasim flight model, you have to manually adjust either up or down depending upon the flight model used.

Yet flight gear has a property that defines which fdm is being used and so advanced weather could easily have used an adjustment factor depending upon which flight model was used to get 'closer' to more realism.

And used the GUI adjustment for any fine-tuning desired by the user.

So I think I'll stand by my statement.
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Re: Thermal spawning, ridge wind and weather configuration

Postby GinGin » Sat May 15, 2021 8:57 pm

advanced weather is correct for neither jsbsim or yasim flight model


I think it was written a couple of times that advanced weather was independent of the fdm used . Which is quite a proof of sanity for a weather engine ( in my opinion ).

Neither tailored for jsb sim nor ysim nor whateverfdmsim etc.
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Re: Thermal spawning, ridge wind and weather configuration

Postby portreekid » Sat May 15, 2021 10:02 pm

S&J wrote in Sat May 15, 2021 6:50 pm:So advanced weather is correct for neither jsbsim or yasim flight model, you have to manually adjust either up or down depending upon the flight model used.


If you read it again carefully you will discover that it is not only jsbsim vs. yasim but also aircraft dependent. So you propose a list of Aircraft in the weather engine? Not good design. What do you do if one of the aircraft has been fixed?

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Re: Thermal spawning, ridge wind and weather configuration

Postby cgdae » Sun May 16, 2021 1:26 am

S&J wrote in Sat May 15, 2021 6:50 pm:So advanced weather is correct for neither jsbsim or yasim flight model, you have to manually adjust either up or down depending upon the flight model used.

Yet flight gear has a property that defines which fdm is being used and so advanced weather could easily have used an adjustment factor depending upon which flight model was used to get 'closer' to more realism.

And used the GUI adjustment for any fine-tuning desired by the user.

So I think I'll stand by my statement.


This does not look like a bug in the weather system to me. If anything it's a problem in the FDMs - presumably they should react in a similar way (insofar as that is possible for different FDMs) to turbulence-magnitude-norm?

Even if the FDMs are differently non-linear, if the differences are so obvious at the moment then perhaps some simple scaling within one or both of the FDMs might improve things significantly, even if a perfect solution isn't possible?

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Re: Thermal spawning, ridge wind and weather configuration

Postby Thorsten » Sun May 16, 2021 6:48 am

Yet flight gear has a property that defines which fdm is being used and so advanced weather could easily have used an adjustment factor depending upon which flight model was used to get 'closer' to more realism.

So I think I'll stand by my statement.


I gave the reason why this is not done along with the explanation above - you can stand by your statement all day long and not move an inch, but you won't see me coding a weather system that is FDM-dependent - for the simple reason that this'd be really poor design (if you think ahead just a bit, the current design is robust against introducing a third FDM to FG, or against re-activating the UIUC that was once in...)

So far the facts of the matter so far are that you didn't know the available solution, you didn't bother to search the GUI and you didn't bother to ask nicely, you just thought it fit to throw accusations of a screw-up here. Now that you've received an explanation that the problem is in fact known, analyzed and solved, you try to come up with a reason why you're somehow still right and justified in doing what you do and why someone else did something wrong - yet you fail to actually read the complete explanation that actually pre-empts just that argument. Frankly - I don't care much for that kind of attitude in a discussion.

Even if the FDMs are differently non-linear, if the differences are so obvious at the moment then perhaps some simple scaling within one or both of the FDMs might improve things significantly, even if a perfect solution isn't possible?


It would have to be YaSim though, since JSBSim is also used in stand-alone mode I seriously doubt people will want to change the parameter there and re-do all their standalone scripts...
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Re: Thermal spawning, ridge wind and weather configuration

Postby S&J » Sun May 16, 2021 9:36 am

cgdae wrote in Sun May 16, 2021 1:26 am:
Even if the FDMs are differently non-linear, if the differences are so obvious at the moment then perhaps some simple scaling within one or both of the FDMs might improve things significantly, even if a perfect solution isn't possible?

- Jules


You can't do a simple scaling within the fdm to adjust the property value as advanced weather comes along later and overwrites it.

The solution has to be within the weather code.
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Re: Thermal spawning, ridge wind and weather configuration

Postby benih » Sun May 16, 2021 10:06 am

Just asking again to make sure i understood it correctly.
- When tuning turbolences to 0, does this affect the thermal generation, and if yes, how?
- what are the changes regarding thermals when the convective-slider is adjusted (both ways)?

[edit] an additional question diected towards an idea for implementing a thermal-visualization-map: how are the thermals generated, can i somehow probe the environment for the updrafts in a nasal loop?
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Re: Thermal spawning, ridge wind and weather configuration

Postby Johan G » Sun May 16, 2021 11:20 am

S&J wrote in Sun May 16, 2021 9:36 am:You can't do a simple scaling within the fdm to adjust the property value as advanced weather comes along later and overwrites it.

There is an interface between the weather models and the FDMs from where a FDM get the parameters of the atmosphere at the aircraft's position. But just as a weather model probably should not overwrite parameters used within a FDM, a FDM probably should not overwrite parameters used within a weather model.
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Re: Thermal spawning, ridge wind and weather configuration

Postby S&J » Sun May 16, 2021 3:09 pm

I'm not asking for a flight model to modify a weather property I'm just suggesting that the weather based on what flight model is being used create the turbulence settings to values that have a more realistic effect.

How a plane reacts to turbulence should be planeside and so having a GUI in weather to adjust this rather than planeside is counter intuitive. If it wasn't people wouldn't be thanking someone for having it explained to them.

If a user doesn't want turbulence or wishes to dumb down or increase it's effects maybe he should be doing this via a drop down menu like you do other things.
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Re: Thermal spawning, ridge wind and weather configuration

Postby wkitty42 » Sun May 16, 2021 4:32 pm

Thorsten wrote in Sun May 16, 2021 6:48 am:(if you think ahead just a bit, the current design is robust against introducing a third FDM to FG, or against re-activating the UIUC that was once in...)

FWIW: UIUC (aka larcsim?) is back in since sept 2015, i think... i remember reading on the mailing list about UIUC and Larcsim being reenabled back in that time frame...
here's the original message i remember: https://sourceforge.net/p/flightgear/mailman/message/34472084/
there's also this thread from december 2015 that starts with a message from curtis: https://sourceforge.net/p/flightgear/mailman/flightgear-devel/thread/CAHtsj_dw0CVkHOq%3D%2BkUZJPpuuujgUKbPOyd1m5qQR5VC4TUrrg%40mail.gmail.com/#msg34679412


OT - might post in another subforum later:
so i ran a quick search and came up with these craft... this list matches the one that bugman posted in his message linked above...
Code: Select all
find ~/flightgear-dev/fgaddon-ng -type d \( -path *.git* -o -path *.svn* -o -path *.cvs* \) -prune -o -type f -name "*-set.xml" -exec xmlstarlet select --template --inp-name --output " " --value-of "/PropertyList/sim/flight-model" --nl {} \; | grep -Ei -e "(uiuc|larcsim)" | cut -d"/" -f 7 | sort -u
a4
airwaveXtreme150
asw20
beech99
fkdr1
marchetti
ornithopter
sopwithCamel
wrightFlyer1903


so using the lastest NEXT branch, i just flew the "A4D Skyhawk"... not very well via keyboard but i did get it into the air... the controls are not working too well on the ground... at least trying to make it turn while taxiing is a bit ugh...

i also loaded the "sopwith camel 1f.1 (uiuc)" and got it off the ground... it needs some love... for one thing, i saw no way to remove the wheel chocks but i did get it into the air...
i noticed there was the "spowith camel (larcsim)" so loaded that one too... it loaded with the 2D panel on screen and no wheel chocks showing in the external view... i don't know what the FDM differences are, though... i did fly this one, too... it is just as twitchy as the UIUC one... using the term "twitchy" is being pretty generous, too :hahaha:

for s&g i also tried the beech 99... it, too, loaded with the 2d panel... that was a fun one because toggling the 2D panel off... i didn't get this one in the air... didn't try, really... pgup/pgdn seemed to control only the left engine... nothing i did would make the right engine go... i won't even mention that the craft loads with the gear up but looks like it is sitting on the ground with them down...

ok, so enough OT in this thread from me about them... i just wanted to point out that the UIUC/Larcsim FDMs are (back) in FG and have been for several years ;)
Last edited by wkitty42 on Sun May 16, 2021 4:37 pm, 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: Thermal spawning, ridge wind and weather configuration

Postby wkitty42 » Sun May 16, 2021 4:34 pm

benih wrote in Sun May 16, 2021 10:06 am:- When tuning turbolences to 0

FWIW: if i read correctly, this should be "toward zero" not "to zero"... you might end up at zero in some craft, though...
"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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