Author Topic: The Technology of X-Plane  (Read 1001 times)

Offline Zigrat

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The Technology of X-Plane
« Reply #15 on: July 29, 2002, 07:24:22 PM »
whattype of calculation do they do. its gotta be first order, do they use VLM or something similar? To get accurate results with that type of method you need a fine mesh.
They assume laminar flow? Laminar flow can only be assumed below a critical reynolds number, and then only if they surface is free of defects. Plus, the greater the wing sweep the lower the critical Reynolds number since there will be a greater amount of spanwise flow.

How are they calculating drag due to seperation? Theres no way to do that "on the fly". What about interference drag? Cooling drag. Wave drag. Base drag. I am just interested how this magical program can calculate all of these parameters in real time :) Since in my work (Phd student in aerospace engineering) calculating these things (if they can be calculated at all, which many of them really cant without CFD and then not very well) takes minutes to hours, not milliseconds.

Offline Innominate

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« Reply #16 on: July 29, 2002, 07:44:49 PM »
A couple of problems,

first, X-plane doesnt model stick forces, so you could figure out how a 190 would roll with hydralic control surfaces. :D

second, airfoil shapes are modeled more the traditional way, than by drawing a cross-section.

It's worth noting that, untill a couple of versions ago,  looping in X-plane was impossible.


An excellent sim though.

Offline senna

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« Reply #17 on: July 29, 2002, 09:32:06 PM »
Roman guards, sieze that man! Bring him to the Gladiator arena at once.

:D

Offline Upchuck

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« Reply #18 on: July 29, 2002, 10:15:59 PM »
Who is Deezcamp?  

I am not Deezcamp, whoever he/she/it is.  

You folks really need to calm down about this.  I'm sure this Deezcamp has probably oversensitized all of you to the subject, but all we did was mention a different sim than AH and try to point out that it allows some interesting possibilities that AH doesn't.  

Zigrat, I never said it calculated all the details of drag you mentioned.  I simply said it calculated the lift for several points for each flight surface.  I don't know the detail to which it calculates them.  I do know it does a believable job of simulating flight via this method.  Yes, X-plane does have weaknesses in non-laminar situations and loops, as well as other areas.

Toad, I never said X-plane was the end all, beat all of flight sims.  I never said it was better at simulating aerial combat than AH.  I never said it was a combat flight sim at all.  Beyond that I'm sitting here wasting my precious time on these boards, not on X-plane's boards.  Doesn't that tell you something?

Thank you for the input, Hitech.  I don't think the basics of the flight model have changed much in X-plane, but I haven't followed it much since 6.0 came out about a year ago.  I appreciate your sharing some of your knowledge of how it works.  As far as engine modelling goes it is pretty basic, but the point of the sim isn't engine modelling, and at least it includes fuel mixture.

I was just trying to point out X-plane's strengths because everyone reacted so automatically without taking the few moments of thought it would take to learn a little about the program you're belittling.  

I think Senna's comment points out the attitude of this board regarding comments about X-plane quite well.

Offline steely07

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« Reply #19 on: July 30, 2002, 03:15:01 AM »
I used to fly a lot of XPlane,went around the world in a 767,lotsa autopilot of course,but did vectored approaches at all field's that had the facility.........
 i have only one question,can you stall properly in xplane yet,i am aware that AH does not have exactly modelled stalls,but the last version of xplane i tried (bout ver 6.something),and all previous versions it was impossible to loop and the stall seems IMHO wrong.
 That said,i wonder where deez went...? :)
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Offline Hristo

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« Reply #20 on: July 30, 2002, 06:54:38 AM »
Quote
Originally posted by Chairboy
.

In response to a snarky comment above, yes, it  does have what it takes to figure out the roll rate at 13,500 ft while flying at 300IAS.  Air density is integrally modelled.


English is not my 1st language, so I might need help on what "snarky" means.

Anyway, while I appreciate the effort, why go thru all of it when pilot strength isn't modeled ? As someone said above, all you can model there is a 190 with hydraulically boosted ailerons.

So, in short, it doesn't have all it takes to calculate roll rate at 13,500 ft and 300 IAS. You'd need to model a LW 27 y.o. Hauptmann who had ersatz tee and butterbread for breakfast.

Offline Toad

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« Reply #21 on: July 30, 2002, 07:20:43 AM »
Upchuck, do a search for "X-plane" with the author as "deezcamp".

After a few hours reading, you'll probably realize why this thread drew the reaction that it did. Unless you ARE deez, then of course you know. But I don't think you are... he wouldn't remain civil for two posts. :D

Bottom line for me with X-plane is that it is an interesting development in PC simulation. However, I never was a "Microsoft Flight Simulator" type person. Bores me to tears to fly around in civil aviation type stuff pretending I'm REALLY a C-172 driver on a cross-country from Moline to Chicago. Woohoo.

Also, I'm not designing or building any type of aircraft or ultralight nor modifications for same.

I'm just having fun blowing stuff up. So X-plane at this stage doesn't interest me in the least. Now... if it were to get guns and go MMOG..... well I'd surely take a look.

PS: I don't play the excellent Sherwin-Williams house painting simulation either.
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Offline ergRTC

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« Reply #22 on: July 30, 2002, 07:28:49 AM »
I have to agree that the 'snarky' comments are a bit much.   Back when I didnt no diddly about web development, I thought crap like php and cold fusion were just expensive (or free) toys to keep the average joe from working on the net.  

Then I found out what kind of a mess static programming is.  I think this may be another situation.  x-plane sounds like it is trying to do what should have been done from the start.  Make a dynamic system working from physics where you spend the majority of your time tweaking the equations, improving the program, and not personally nurseing individual flight models from scratch each time.  

I am sure it will be years before it works like it should and performs like we want it too, but in the end, if they succeed, its going to make hitechs life a little easier.  At that point he can start pumping out all kinds of planes, with wicked art and we can all be happy.  Maybe he could fix the trees after that.  Put in more gvs and improve other parts of the game.  

Why may this be possible?  Cause somebody is trying.  Looks win win to me.

Offline hitech

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« Reply #23 on: July 30, 2002, 08:49:55 AM »
Upchuck, don't take this the wrong way, x plane is very good for what it's trying to accomplish. It's just not the "holy grail"  and use very simalar modling techniques to ah.

Engine modling (NOT how the pilot manages engines) is extreamly inportant in a combat sim, it's what gives a plane accurate climb rates and speeds, over the entire range of altitude and speed. This is not a problem in Xplane because they are not doing plane v plane matchups.


HiTech

Offline Upchuck

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« Reply #24 on: July 30, 2002, 09:20:04 AM »
I should say I am not an X-plane expert by any means.  Even when I was keeping up with it I was fairly lukewarm and mediocre, and I haven't followed it in any real way for over a year.  Neither am I an AH expert, the most I can come up with these days, due to time constraints, is an occasional foray into H2H for a merciless spanking.

Yes, Steely07, X-plane does have problems with near stall and stalled situations because it's flight model is intended primarily to simulate laminar air flow and stalled and near stall conditions are defined by their lack of laminar air flow.  I have a feeling this is why loops don't 'work'.  It IS possible to loop in X-plane, but some aircraft will not, and those that do often have a slight rotation near the top such that it is difficult to impossible to come down still in line with the heading you came in on.  This rotation happens in some non-prop rides as well as props.  For this reason, and others, I don't think this rotation is due to torque.  I can manage torque in loops in AH and other sims that model torque etc. without a problem.

I have to agree with Toad that the idea of simply flying from one point to another is mindlessly boring.  There are 'Virtual Airlines' for sims like X-plane where you are assigned a flight from point A to point B, and I never understood the attraction.  However, for those of us who may dream of one day obtaining a pilot's license, but have never had the time and money together at the same time to actually do it, a sim like X-plane offers some interesting possibilities.

However, there are other features that do attract me.  X-plane allows random failure of a wide variety of systems, not unlike taking damage from a bogey on your tail, only these failures happen without warning (you can't see the bogey coming) and there is no ctrl-D button that will tell you instantly what's busted.  So you have to actually check your aircraft out to see what's wrong and what you need to do to survive.

It also allows simulation of more than 190 roll rates.  You can play around with taking the Space Shuttle all the way from re-entry to the ground, or launch a Saturn V rocket, not to mention the fun of trying to turn a plane in the ultra thin atmosphere of Mars.  It may not simulate all of these perfectly, but at least it tries.

X-plane also simulates more than bright sunny near cloudless summer days in Texas.  It rains and snows in X-plane, visibility deteriorates, ice builds up, lightning strikes and so on.  You can download real time weather data for the entire globe and fly in real time weather conditions anywhere in the world.  Oh, and the water actually has waves! (They are all of a uniform size and spacing, moving at a regular rate, but at least they are there!)  Landing a floatplane in the waves can actually be tricky!

Another thing I like about X-plane that no combat flight sim will ever give you  because they can't force their players to work at finding a fight, is you actually have to navigate!  True, you can still get a simple 'You Are Here' marker, but if you ignore that you can actually do a full IFR flight, and get lost!  With the new updated terrain data they've added since I last updated I hear you can actually navigate by VFR as well.

Finally, as I implied I still prefer AH, primarily due to a fascination with WWII and it's history and the aircraft.  Oh, and I also like to blow things up too, I just suck at it.  Which reminds me, when is AH going to get a B-24?  I want to simulate the Ploesti raids!

Offline Innominate

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« Reply #25 on: July 30, 2002, 09:28:28 AM »
Upchuck, it's worth noting that the looping problem was fixed, so looping now works like it should.

Offline Upchuck

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« Reply #26 on: July 30, 2002, 09:35:50 AM »
Thanks for taking the time to help me understand, Hitech.  It's greatly appreciated.  I don't think I fully understood what you meant earlier.  And I hope my comment about fuel mixture wasn't taken as a slight against your work.  It wasn't meant as such.  I considered deleting it because of that after I wrote it, but left it in just because I wish it were modelled.  However, I understand a lot of people who play games like this don't consider such mundane things to be 'fun'.

 I don't consider X-plane the 'holy grail', after all it doesn't allow combat and competition which I honestly find more interesting over the long run, but it does allow some different things that I can't find here.  Now, if someone could combine the two worlds for me...;)

Offline hitech

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« Reply #27 on: July 30, 2002, 12:05:58 PM »
Upchuck what it realy comes down to is what is the sim designed to accomoplish. AH is first and formost a combat simulation.

In Xplane, navigation,avoiding stormes, is a key piece of what the fun is.

In AH the primary goal/fun is fighting, and navigation can become a more of a distraction than enhancing the game.

The designer of a game must spend his efforts on what will attacts the most customers for his given goal. You don't see mass multiplayer with lots of weapon systems in xplane,items like live voice, chat buffers,excetera. It's not there because it's not what the sim is trying to accomplish. But the lack of those items dosn't lesson what it is trying to do.

A good deal of our effort is spent on these types of items.

And my holy grail reference is just do to the big word hype that some games try to use, where in reality there method of modling is very standard. Infact even lamar flow in modling realy is just different lift/drag/cm/cp curves and is no different in modleing than none lammanar flows.

BTW you are deffinatly not DeeZeeCamp.

We hare haveing a very civil discussion, with DZC it wasn't a discussion, his desire was simply to promote XPlane, and not to find out what other people think.

HiTech

Offline jbroey3

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Legendary... .. I dont get it.. but hey.
« Reply #28 on: July 31, 2002, 05:19:34 PM »
hehe... This is very funny indeed.

:)  Well, TO let you ALL know. I am DeeZCamp :)


The cat is out the bag so to say, Hitech I applauded your efforts then, and I still do now.  Albiet, I have not flown in Aces High for quite some time. I have been to busy persueing my real flight training.  :)

You have an excellent product, It does as you have set it out to do and this is multiplayer combat on a larger than 64 players scale with a pretty good fidelity of modeling each individual aircaft.

It is in my opinon that the Flight modeling, or rather the way each aircraft react in Aces High, is somewhat less "real" than compared to X-plane. Im sorry I feel this way, I think others do as well.

Here are my points.
1. I do think that realtime calculations are the way to go.  

2. "In my opinon", the aces High flight model, just as a comparison to xplane is more "static" and less fluid. Given the same situation in an observed stall in Aces High compared to X-plane, ones of which involve extreme angles of attack, X-plane wins hands down.

3. From what I have noticed in Aces High, is that there seems to be a certain region of predetermined movement that may contradict what that particular moment in time of movement for an aircraft displays.

It is sad to see many are still blindly trash talking x-plane, considering that some of those doing the talking have never tried it, nor flown in reality.   :(

Anyhow.. HTC keep up the good work for the entire war that your creating in Aces High..   As for X-plane, I sure hope that you are not simply dismissing xplane as well.  

I do look forward to eventually joining Aces high once more, and hopefully a Ground war will exist by then as well :)

Later alle. :)

Offline straffo

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« Reply #29 on: August 01, 2002, 01:54:02 AM »
Deez (or jbroey3 ;) ) Just consider that all developper face the same dilemns :

The quantity of horsepower (aka megahertz) is finite ...
The quantity of worktime per day is finite ...

You have to made choices but what you have to do essentially is to please your customer (they pay you ya know ;))