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Turning off turbulence

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Turning off turbulence

Postby daveculp » Fri Nov 21, 2014 7:22 pm

I've had trouble in the past with being unable to turn off turbulence, and my solution then was to sever the link to the FDM. What I'm exploring now in FG 3.2 is using the configuration files to stop turbulence, but I'm having no luck. The property /environment/turbulence/magnitude-norm is set to 1.0 and I can't change it to zero, which means it's being controlled from somewhere in the sim.

The Weather Conditions dialog shows the Manually Configure Weather box checked. The Basic Troposphere Weather Conditions shows all Turbulence boxes set to "none". I edited environment.xml to set the scenario to "Manual input", although I'm not sure this does what I think. Does it mean I control weather by entering parameters for each atmosphere layer, or does it mean I need to manually enter a METAR? I also set the turbulence "factor" and "magnitude-norm" to zero for each layer. I also set /turbulence/sensitivity to zero. I also set JSBSim turbulence model to ttNone.

I'm still getting full turbulence. Any ideas? (using F-105 model, departing fron KNUQ)
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Re: Turning off turbulence

Postby Hooray » Fri Nov 21, 2014 7:33 pm

In FlightGear, there's also a dedicated subsystem causing terrain-induced turbulence (FGRidgeLift), see $FG_SRC/Environment/ridge_lift.?xx for details - I am not sure if its properties are documented elsewhere, but back when it was implemented, properties were added for controlling/disabling the system. Apart from that, there's obviously also the Advanced Weather system, which is primarily implemented in scripting space and extensively documented on the wiki - it can be disabled by using "Basic Weather" instead.
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Re: Turning off turbulence

Postby daveculp » Fri Nov 21, 2014 7:40 pm

Thanks Hooray. I'll look into disabling the ridge lift. How does one enable "Basic Weather"?
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Re: Turning off turbulence

Postby Hooray » Fri Nov 21, 2014 7:44 pm

There's a dedicated environment/weather dialog where you can switch between BASIC/ADVANCED weather - the latter is much more compelling, and generally "slower" due its scripted nature (the underlying control logic is in Nasal, while visual stuff is implemented using effects/shaders) - while the former is much less flexible, but more responsive overall due to its hard-coded nature and reliance on "property rules" (=Autopilot PID controllers), i.e. XML logic mapped to C++ data structures.
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Re: Turning off turbulence

Postby daveculp » Sat Nov 22, 2014 12:22 am

Thanks Hooray. I tried to turn off ridge lift by adding:

Code: Select all
  <ridge-lift>
    <enabled type="int">0</enabled>
  </ridge-lift>


to environment.xml. It had no effect, so maybe it was off anyway. It appears that basic weather is enabled at startup, according to the weather dialog, so I'm at a loss to explain where the full-on turbulence is coming from.

--Dave
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Re: Turning off turbulence

Postby KL-666 » Sat Nov 22, 2014 1:02 am

I have moved heaven and earth to get some real weather effects like turbulence. And here i see people wanting to get rid of it. Well, everyone has their own likes. :-)
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Re: Turning off turbulence

Postby daveculp » Sat Nov 22, 2014 1:29 am

I realise the gamers really like the direction the weather code is going, but for FDM people it stinks. I'm going through jsbsim.cxx and flight.cxx snipping out the wind inputs to the FDM and so far no help. With so much code in scripted space now the turbulence could be coming from anywhere through the property tree.
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Re: Turning off turbulence

Postby Johan G » Sat Nov 22, 2014 11:02 am

I think that for FDM developers/testers having the option to use a completely still ISA (International Standard Atmosphere) would be golden. Maybe there are ways to achieve that akin to opt out all weather code on startup.

Edit: This could also be good to have when beginning dead reckoning navigation training.
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Re: Turning off turbulence

Postby D-EKEW » Sat Nov 22, 2014 11:35 am

+1
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Re: Turning off turbulence

Postby Hooray » Sat Nov 22, 2014 11:40 am

right, I agree - I think that other FDM folks have made similar remarks, e.g. hvengel and bomber.
The thing is, you cannot expect changes to be caused by participating on the forum - it would be MUCH better to file a feature request at the tracker, make your case there and then do some "promotion" via the forum/devel list to get others involved, so that they can provide feedback/support.

In general, there should be no turbulence induced via scripting space once AW/LW is off.
Basic Weather is supposed to be the default system - and shouldn't contain any scripted workarounds - in fact, its primary developer has repeatedly objected when it came to new Nasal additions.

The underlying problem is, and remains, that I/O and data flow dependencies are not made explicit currently, so that it's difficult to track what's going on.

Personally, I'd first of all verify if the problems persists without FG, i.e. in jsbsim standalone and then proceed step-by-step.
If in doubt, use the minimal startup profile, which is probably pretty close to what you need ISA-wise, or which could at least be easily adapted accordingly.
Please do feel free to update the wiki accordingly.
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Re: Turning off turbulence

Postby Thorsten » Sat Nov 22, 2014 12:13 pm

What I'm exploring now in FG 3.2 is using the configuration files to stop turbulence, but I'm having no luck. The property /environment/turbulence/magnitude-norm is set to 1.0 and I can't change it to zero, which means it's being controlled from somewhere in the sim.


I've just tested this with current GIT, I can't reproduce that at all.

Using a manually configured Basic Weather scenario with turbulence all set to 'none', I'm getting /environment/turbulence/magnitude-norm varying from ~10^-5 to maximally 0.025. I have never experienced turbulence stuck at 1.0 during any flight with any weather system (surely lots of users would riot if FG would work by default like that...) - so I would suspect the problem is somewhere on your end, perhaps a custom config?

Using AW, I get the turbulence set by the AW management (where for calm winds it's usually absent) and found it to be set to zero as expected.

Ending AW and switching BW off as well via /environment/config/enabled I could set the turbulence property by hand to any value I wanted.

So the FG environment system here is working just as it should be.

I think that for FDM developers/testers having the option to use a completely still ISA (International Standard Atmosphere) would be golden. Maybe there are ways to achieve that akin to opt out all weather code on startup.


We've had /environment/config/enabled for a couple of years now - this leaves a bare state of the atmosphere where you can set wind, visibility, sea level pressure and temperature by hand and all you get is the ISA altitude extrapolation of the atmosphere. We have discussed the requirements in depth on the mailing list before TorstenD coded it.

We have in addition the option to fetch METAR but not execute it (/environment/params/metar-updates-environment), to fetch METAR for a different place and a couple of other nifty things.

Why don't you simply use it?
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Re: Turning off turbulence

Postby Johan G » Sat Nov 22, 2014 4:50 pm

Thorsten wrote in Sat Nov 22, 2014 12:13 pm:We've had /environment/config/enabled for a couple of years now - this leaves a bare state of the atmosphere where you can set wind, visibility, sea level pressure and temperature by hand and all you get is the ISA altitude extrapolation of the atmosphere. We have discussed the requirements in depth on the mailing list before TorstenD coded it.

We have in addition the option to fetch METAR but not execute it (/environment/params/metar-updates-environment), to fetch METAR for a different place and a couple of other nifty things.

Why don't you simply use it?

Because I simply was unaware of it. :wink:

Maybe this newly created wiki article could be helpful to other: Howto:Get the standard atmosphere (even though I guess it is incomplete and may not be entirely correct).
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Re: Turning off turbulence

Postby daveculp » Sat Nov 22, 2014 8:56 pm

Thanks Thorsten. I looked for "/environment/config/enabled" and couldn't find it in either preferences.xml or environment.xml. I would keep looking, or just add it myself, but I found a quick solution that works great for me. In /src/FDM/JSBSim/models/atmosphere/FGWinds.h, line 200 is changed to read: virtual void SetTurbType(tType tt) {turbType = ttNone;} . This effectively innoculates the FDM from turbulence.

Why don't you simply use it?


This is why I don't submit a feature request or bug report. The answer is always so pat. And I don't visit the devel list either, because that unhappy place would be even unhappier if I was there.
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Re: Turning off turbulence

Postby Thorsten » Sun Nov 23, 2014 8:20 am

I looked for "/environment/config/enabled" and couldn't find it in either preferences.xml or environment.xml.


I suspect its existence is hard-coded - not all the properties in the trees are generated from xml files. You can set it runtime with the property browser or with a Nasal setprop(), and (I haven't tried) you might be able to add it to the environment xml.
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Re: Turning off turbulence

Postby Bomber » Fri Nov 28, 2014 11:41 am

Making it easy to test a flight model in an FG controlled environment should not require a request it should be a given and never have been taken away.

But what the heck
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