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Better nort crash

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Re: Better nort crash

Postby Algernon » Mon Jun 09, 2014 11:09 am

Johan G wrote in Fri Jun 06, 2014 1:36 pm:
StuartC wrote in Thu Jun 05, 2014 9:46 pm:Because this will happen, soon.......

It is a good start, but I think that it disintegrates a bit much. :wink:

I've only just had time to properly digest your helpful notes, which on the whole I agree with and I think Tomaskom, our aerodynamicist whose work the disintegration effect is, will find it helpful to tune the scenarios. My impression is that, as you say, it's a start - Tom produced it remarkably quickly, but he has some exciting stuff going on in his professional life at the moment and it will improve when he has more time. I don't know how collisions are detected - the code has not yet been released, it's part of the L-159 development - but I would imagine it will support, for example, the loss of a single wing, a broken gear unit etc.

My view on the realism is that the progressive nature of problems or damage is of principal importance. The damage script you've seen in action on the Victor engine works, as I've said in another post, on the principal of failure probabilities. Damage zones are Nasal objects, each of which has a failure probability which increases according to damage to itself or nearby zones. A problem like low oil pressure on an engine should not be dangerous if the engine is shut down correctly and in good time; a problem like the loss of a flight surface at altitude is likely to induce flight conditions in which other zones will fail - e.g. a wing comes off, the aircraft plummets and spins, the airframe is overstressed and fails in various places at different times. If Tom and I can integrate our work successfully, you should get an inherently more realistic disintegration which hopefully will also affect the FDM.

StuartC wrote in Fri Jun 06, 2014 1:15 pm:How about a bird strike knocking out one or more engines ?

Ooh, nice. :D

Brings this to mind: "Hit birds. We've lost thrust on both engines. We're turning back towards LaGuardia." :wink: Time flies, it's already five years ago.

Yeah, I recently re-read the stories as part of my birdstrike - can't believe it's that long ago!

I realized that a bird strike script could sample the terrain land class and increase the possibility for a bird strike in certain conditions, like where water and land meets, along beaches and over wetlands, as well as increase the possibility at lower altitudes. Something for the future I guess.

Yes indeed. I believe bird activity close to airports can also constitute part of a METAR report. At the moment, the birdstrike function is a very basic way of getting a visual representation of the strike (based on the famous footage of, I think, an F-16 student pilot losing an engine to birdstrike) and applying some damage - it's tied to the aircraft model, not free roaming, and in this form, would be part of a random failures system in the aircraft (as previously mentioned, this uses FG's current built-in failures system and will continue to do so when galvedro's improved code shows up in V3.2). I am, however, also quite interested in Hooray's AI-controlled birdstrike script - with Nasal support in AI scenarios, a "Random Hazards" scenario could determine likely bird locations and spawn a flock of them. A collision with the flock would result in some calculations as to the likely number of birds ingested and call the hit function of appropriate damage zones (engines mostly, but potentially other places... windscreen even?! (But then we have to model decompression also, which I quite fancy doing!)

UPDATE: I've written something for the newsletter now about this, with three videos embedded. If you're interested in Tom's fireball, now being implemented by Stuart on some of his development aircraft, this video shows its original application, as the explosion resulting from a V-1 impact. As you can see, there's little frame-rate loss from such a big explosion and resulting smoke column, even with another fire burning and many MP aircraft close by.

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Re: Better nort crash

Postby Hooray » Mon Jun 09, 2014 3:20 pm

This is all looking very promising, but you guys should really be aware of galvedro's work, and flug's bombable addon - there certainly is quite some overlapping code in all 3 efforts here, and it would make sense to generalize and unify things so that code can be better reused.
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Re: Better nort crash

Postby Johan G » Mon Jun 09, 2014 3:27 pm

About the fireballs, I am not sure as of how you guys have done that, but if you have used some kind of buoyancy try lowering it a bit. The smoke is rising a bit fast even for a secondary fire, and way too fast for the primary explosion and fire.

Also, most high explosive (HE) bombs, have a short flash then kicks up a lot of dirt, often mushrooming. In a humid environment on can often see the shock wave though.

Two videos with examples, first a compilation of aircraft crashes and then JDAM (using the same HE iron bomb body as the venerable Mk 84 2000 lbs bomb with the addition of a fin kit with guidance) and finally a V1 explosion.





This YouTube video (starting at 3:50) has one of the few V1 explosion I have found.
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Re: Better nort crash

Postby Algernon » Mon Jun 09, 2014 4:05 pm

Hooray wrote in Mon Jun 09, 2014 3:20 pm:This is all looking very promising, but you guys should really be aware of galvedro's work, and flug's bombable addon - there certainly is quite some overlapping code in all 3 efforts here, and it would make sense to generalize and unify things so that code can be better reused.

Yes, I'm all for that. As far as Bombable is concerned, we're naturally interested in any way to cause a hit on a damage zone, including those already existing in FlightGear, but after that, I'm not sure there's a lot of similarities - that is only one cause of damage. As I visualise it, there is a bottleneck where different systems must come together - the AI/MP properties - assuming, as I am, that we'll be continuing to use the existing MP protocol in the foreseeable future. Once we start looking at combat hits, we'll almost certainly be comparing flug and dfaber's work on projectile hits so that our method of reporting submodel hits allows compatibility where possible. Tom has already built a method of seeing tracer from AI and MP models which also checks for collisions using submodels, so our next step is to address hit compatibility and how hits are passed over MP.

But as far as failures go, I am quite keen to find galvedro's code to find out how the failures system is changing - my intention all along has been to keep pace with FG's built in failures and adapt the damage system accordingly to make the best use of it. I'm looking through the repository at the moment but haven't yet found it. The damage system is intended to be a stage between hits and failures - failures may happen anyway, but failures are more likely to result where there is damage; to what extent will be handled between the damage script and the built in failure system. That said, I still think there will be room, a need even, for more detailed modelling of individual aircraft's particular characteristics - as an example, I've been looking at the failure probabilities for an EE Lightning, they will be significantly more prone to engine fires than the Victor!
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Re: Better nort crash

Postby Hooray » Mon Jun 09, 2014 4:21 pm

Algernon wrote in Mon Jun 09, 2014 4:05 pm:I'm looking through the repository at the moment but haven't yet found it.


See the right-hand box at: http://wiki.flightgear.org/A_Failure_Ma ... FlightGear
But I think it's already merged, so just check $FG_ROOT/Nasal/FailureMgr: https://gitorious.org/fg/fgdata/source/ ... FailureMgr

To see the whole commit/diff, check out merge request #253: https://gitorious.org/fg/fgdata/merge_requests/253

For example, see: https://gitorious.org/fg/fgdata/commit/ ... 838801359f
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Re: Better nort crash

Postby Algernon » Mon Jun 09, 2014 6:25 pm

Ah, easy when you know where! :) Thank you for the links.
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Re: Better nort crash

Postby galvedro » Thu Jun 12, 2014 8:01 am

Hi guys!

Since you are actually doing failure/damage/wear modeling, I am very interested in hearing your feedback about the new failure manager architecture and functionality.

I would suggest to read the wiki page Hooray posted first, as I tried to document the motivation for the change and the design principles there. The public interface for programming the failure manager from Nasal is at Nasal/FailureMgr/public.nas. It should be reasonably documented, but please let me know if you find something confusing or unclear.

On a side note, I don't recommend using the property tree interface directly for new developments, as it is currently half way between what it was and what I want it to be, so it is a bit dirty right now and it will change a bit in the future.
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Re: Better nort crash

Postby Algernon » Thu Jun 12, 2014 12:05 pm

Hi :) I'd certainly be happy to feed back my experiences with the new code. I presume I can just grab it from Gitorious and put it into my $FGROOT/Nasal folder to try it out now?

Currently, the damage script has a temporary command to automatically alias unserviceable properties in the current failures to the respective boolean properties in the engines. This can be made much more sophisticated at any time, so once I have an idea of what your code does and how it does it, I shall indeed try using the public API and let you know how I get on. Thanks! :)
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Re: Better nort crash

Postby Hooray » Thu Jun 12, 2014 1:53 pm

if you can, it would probably make sense to use fgdata/master, or maybe wait for the upcoming release, which should everything in place without requiring manual file management and/or git

PS: @Algernon: Great to see that you're actually interested in collaborating here and using existing code - it is very frustrating to see other efforts whose contributors don't realize how heavily their work is related, and how much it would make sense to team up with others to collaborate in a more framework-centric fashion, rather some aircraft-specific feature. We've recently seen several efforts with little to zero communication and collaboration, where contributors could have save months of work had they spoken up earlier and had they shown willingness to collaborate.

The added advantage here is that galvedro's code is a good foundation to work with, i.e. his code is exceptionally clean and he's obviously very familiar with coding, so a joint effort can be a mutually beneficial experience for all parties involved, and you'll save a ton of work and time along the way, while also ensuring that your work is generic, i.e. can be easily reused by other aircraft/developers.

Regarding damage modeling WRT combat/bombable, I'd like to check flug's code at some point to see if/how certain parts of it could be generalized there - even just moving useful routines to a dedicated module in $FG_ROOT/Nasal or $FG_ROOT/Aircraft would be a good thing in my opinion. Flug has written some very clever Nasal code as part of the bombable addon, and we should really try to understand how to generalize and integrate the most useful parts so that people working on similar features can reuse his work.

EDIT: bombable.nas: https://github.com/bhugh/Bombable/blob/ ... mbable.nas
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Re: Better nort crash

Postby Algernon » Thu Jun 12, 2014 7:36 pm

Ah yes, my preferred option would be to wait until the next release actually, I dislike modifiying my FG install too much.

We're definitely keen on using existing code where possible, I will admit that I need to look outside my own development sphere more as it's too tempting just to code something for hours, for fun, which is probably already extant somewhere! I believe galvedro has mentioned somewhere in a post he's interested in overhauling the Electrical.nas script - that is somewhere I'd be very interested to collaborate - battery drain and charge, AC and DC circuits, reasonably realistic load characteristics... that's something I'm excited about! I'm also always keen to get a firmer grip on Nasal, mine is still extremely basic and fairly inelegant.

Thanks for the bombable link - it's been a while since I looked at it, and now my Nasal is better, it makes more sense. First thing I notice - it uses mp_broadcast.nas, which I had assumed it did, and that's also the way I've envisaged transmitting hits across multiplayer. We could certainly look at compatibility there, using the same broadcast primary perhaps. I think we might be using different approaches for cannon fire, however I'm keen on a compatibility approach where there is a certain freedom to model any kind of damage-inflicting item, but using the same protocol to exchange hit and damage information with other similar systems.
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