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-   -   Potentially serious FM/DM issue (http://forum.1cpublishing.eu/showthread.php?t=18663)

B25Mitch 02-11-2011 02:03 PM

Potentially serious FM/DM issue
 
Hi everyone,

I'm usually a pretty quiet member here but I would like to bring this issue into the spotlight. There a damage model bug that was present in IL-2, and seems to be carried over into CoD. The problem is that all aircraft retain their center of mass, even when missing entire wings. Here are two shots from IL-2 1946 showing the results:

http://img708.imageshack.us/img708/8354/crash1.jpg

http://img525.imageshack.us/img525/6782/crash2e.jpg

As you can see, in these screenshots (in which the aircraft is at rest) the remaining wing is magically balanced up in the air. In both cases gravity should pull the remaining wing down. Think of what happens on a see-saw, when the weight on one end is removed.

I had hoped that CoD would start treating wings as having mass, but a few days ago this image surfaced:

http://img703.imageshack.us/img703/167/crash3.jpg

It's pretty clear that the same issue is occurring here, and the intact wing simply does not have any mass. Other people have commented on the unnatural resting position of the plane, but I think it is necessary to properly diagnose the problem.

Now of course this is not only a damage model issue, but a flight model one as we all know wings are routinely 'sawn off' in flight! It would be interesting to see how the dynamics of a wingless plane would be affected if the offset center of mass were taken into account...

PS - I know that it is surely to late for a change to be implemented by Oleg's team in time for the release (assuming of course my 'diagnosis' is correct), but I would hope that a patch may eventually address the issue.

Please comment, regardless of whether you agree with me or not :)

Strike 02-11-2011 02:16 PM

+1 excellent point B25Mitch!

In my opinion this is a horrible sight when showing a simulator that has advanced damage and physics models. That plane, unless it's leaning on the tree, should be wings level because of the force of gravity pulling it down. Theoretically if the hurricane had an extremely heavy radio mounted behind the pilots headrest, which was equal in torque force derived from the wings length from center x force(weight of wing) it would rest in the displayed position if it ended up there perfectly after the crash...

just saying.

And don't math/physics flame me if you know what I'm trying to say but would say it differently because you are smug. ;) Ty in advance

robtek 02-11-2011 02:17 PM

Everything is alright with this pic, only the right landing gear is missing. :-D

JG52Krupi 02-11-2011 02:17 PM

Regarding the last pic it could easily come to a rest like that if it become stuck in the ground, they should spend time polishing over areas of the game.

Clearly you spend a lot of time starring at your crashed aircraft to care about it so much :), I'm sure it will be miles better than the original

norulz 02-11-2011 02:18 PM

I'm also curious how that Spit got in that position in the first place. maybe it had came from down right of the picture and spin near that tree... otherwise, that wing is really magic.

but... IMHO we will see the same "behavior" of crashed planes... I hope I'm wrong but...

Strike 02-11-2011 02:19 PM

Quote:

Originally Posted by norulz (Post 222659)
...curious how that Spit got in that position...

Born Luftpilot I presume... ;)

TheSwede 02-11-2011 02:20 PM

Quote:

Originally Posted by norulz (Post 222659)
I'm also curious how that Spit got in that position in the first place. maybe it had came from down right of the picture and spin near that tree... otherwise, that wing is really magic.

but... IMHO we will see the same "behavior" of crashed planes... I hope I'm wrong but...

The spit?

I hope you check your eyes before release mate.

;)

EDIT: Ah Strike you beat me to it.

JG52Krupi 02-11-2011 02:21 PM

Quote:

Originally Posted by norulz (Post 222659)
I'm also curious how that Spit got in that position in the first place. maybe it had came from down right of the picture and spin near that tree... otherwise, that wing is really magic.

but... IMHO we will see the same "behavior" of crashed planes... I hope I'm wrong but...

Spit... :D when your out purchasing bob go to specsavers

EDIT: Lol were a prickly bunch

The Kraken 02-11-2011 02:22 PM

I don't think the physically correct flight model of a wingless plane has to be overly accurate. If simplifying the physics like that saves some CPU cycles and time for modeling/coding, then why not. It sure doesn't qualify as a bug for me. Anyway I think it's too early to conclude how it will work in CoD - all we've seen so far in that regard are two shots of probably the same scene. I'd assume the center of gravity will in fact move now (like when using up fuel) - even if it wasn't modeled in Il2.

Ploughman 02-11-2011 02:27 PM

Good point Mitch, that Spitfire's certainly got something wrong with it.

B25Mitch 02-11-2011 02:29 PM

I agree with all the feedback here so far (yes, even you, Kraken :) ) in that it isn't really that important how a tumbling plane falls when it's missing a wing, but considering all the complex properties of a wing (lift, collision shape, etc) it surprises me that mass isn't one of them. Anyway, I guess it's no good complaining - as others have mentioned it's probably OK to dismiss the strange angle as a result of uneven ground or hidden objects in the grass.

Sven 02-11-2011 02:31 PM

Yep definatlely something wrong with that B17 in that last picture right there:grin:

On a serious note, this is rather weird and should be implemented as it is a simple law of physics, of course there are situtations where this occurs, but in IL2 it is a little to frequent. I hope they look into it, but I doubt if this will effect the actual FM of the plane, it's almost impossible that they would leave out gravity..

Flying Pencil 02-11-2011 02:46 PM

Quote:

Originally Posted by The Kraken (Post 222670)
I don't think the physically correct flight model of a wingless plane has to be overly accurate....

Actually, it could!

In the virtual world what is displayed is not necessary accurate to how the vehicle handles!
To reduce complexity developers often take shortcuts and set a point X to represent enough damage on wing as to render it "gone", but the FM still sees enough that it is possible to fly the airplane (although flying sideways).

zauii 02-11-2011 02:52 PM

Omfg, does it really matter how the plane came into the position it is in?...

B25Mitch 02-11-2011 03:14 PM

Quote:

Omfg, does it really matter how the plane came into the position it is in?...
No. What matters is that it is defying gravity by remaining in that position, and the implications that the damage model does not care about center of mass.

Bricks 02-11-2011 03:40 PM

Completely unrealistic, indeed. ;)

Like this obvious fake:
http://www.texarkanagazette.com/news...CRASH_Dora.jpg

Strike 02-11-2011 03:43 PM

Quote:

Originally Posted by Bricks (Post 222739)
Completely unrealistic, indeed. ;)

Like this obvious fake:

Actually, this looks like a crashlanding where perhaps the LH MLG has not collapsed or the skidding has flattened the fuselage so much it's not perfectly circular anymore and rests on the "flat" area instead of rolling over. Seeing that we cannot see wether gear is extended or not, we have no conclusion yet, but you make a good point.......

... which we must prove to be blasphemy! :) :p

zauii 02-11-2011 03:46 PM

Quote:

Originally Posted by B25Mitch (Post 222722)
No. What matters is that it is defying gravity by remaining in that position, and the implications that the damage model does not care about center of mass.

So the wing weighs more than the center or what are you saying, it should've tipped on the wing?

TheGrunch 02-11-2011 03:47 PM

I seem to recall that we were told that the centre of mass changes depending on fuel flow (obviating issues like the nasty P-51s in IL-2). Perhaps this was ignored because it only affects terminally damaged aircraft. Ought to affect aircraft that have only lost wing-tips and ailerons and rudders, though, ideally.

Rodolphe 02-11-2011 04:17 PM

...

Quote:

Originally Posted by Strike (Post 222742)
Actually, this looks like a crashlanding where perhaps the LH MLG has not collapsed


http://aviation-safety.net/photos/ac...-C-d-2-750.jpg


http://aviation-safety.net/photos/ac...-C-d-1-750.jpg

The airplane, an ATR-42-320, came down 300 feet short of the threshold runway 17R at Lubbock Preston Smith International Airport, TX.


...

Strike 02-11-2011 04:23 PM

Quote:

Originally Posted by Rodolphe (Post 222760)

Perfect! There you go, thanks.. The MLG wheel is offset, leaving the majority of weight (fuselage) on the right side of the wheel, and the wing (which is obviously lighter than the fuselage) on the left side of the wheel. To tip over, the torque applied from the wing gravity must be greater than that of the entire plane body and is why it hasn't tipped over. My conclusion..

But this is getting off relevance to the initial post..

IL-2 CoD has simplified physics, and you know it

winny 02-11-2011 04:29 PM

The fuselage weighs a lot more than the wings. I think thats the reason for these wing up pics (RL and CoD).

Think of it as looking at a beached yacht.. all the weight is at the bottom, the wing would have generated some lift right up until the point the aircraft stopped moving too which may account for why the plane came to rest there like that (I'm ignoring the fact that it's not 'real' btw).

norulz 02-11-2011 04:31 PM

Quote:

Originally Posted by TheSwede (Post 222663)
The spit?

I hope you check your eyes before release mate.

;)
.

Hey... sorry about my blasphemy :P... I was posting while seeing many pics on other tabs and got confused in the end.

maybe the missing wing was from a spit... you can never know... :-)

So how that... Typhoon got there? :P :cool:

louisv 02-11-2011 04:46 PM

Oleg talked about this picture in the forum, and the spit just made a bad take-off and spun at the end of the runway...Somebody had complained then that it was impossible for the plane to be there because of the nearby tree.

Strike 02-11-2011 04:50 PM

Seriously..... what's up with the aircraft manufacturer and model type mistakes in this thread... next thing you know it's the mosquito

B25Mitch 02-11-2011 05:06 PM

Thankyou Bricks and Rodolphe for posting photos. I think we can say for sure that the weight distribution in real life is much higher in the fuselage than the wings, which means that these kind of raised-wing wrecks are not out of the ordinary.

Perhaps all CoD needs(assuming the collision damage model is similar to IL-2) is a bit of rotational damping on the fuselage to stop it from rolling around so much after it's come to a stop. That would simulate the effects of a 'flattened' fuselage, as seen in the photographs above. Both of the aircraft in my own screenshots reached that position after considerable rocking back and forth, which makes them look a bit like toys, really.

Alien 02-11-2011 06:04 PM

Quote:

Originally Posted by Strike (Post 222662)
Born Luftpilot I presume... ;)

Yeah, all of them answered the question ,,what shot you down?" by telling ,,Spitfire"

Romanator21 02-11-2011 09:28 PM

Mitch, If I'm not mistaken, CoD should implement changing CoG. However, if you look in one youtube video, you can see a Hurricane flying around with only one wing (after hitting a Fiat). Maybe weight distribution is not quite working at this point, or it will be "switched on" at a later point.

http://www.youtube.com/watch?v=bKcL2_-dB0I

(skip to 4:45)

zipper 02-11-2011 09:29 PM

Yeah, I agree with OP ... BUT ... what-can-ya-do-about-it. CG shifts in 1946 are simple changes in trim, there isn't any active mass simulation, pretty sure our 'puters could cope with it, anyway. I'd just be happy if we had something approaching more realistic stalls in CoD, but, if not, I'll deal with it. (I'm almost certain we won't be any closer to groundlooping which would prove Mass modeling.)

zipper 02-11-2011 09:35 PM

OMG - Play That Funky Music!?! What year is it in Russia now - LOL.

Jg2001_Rasputin 02-11-2011 09:55 PM

Quote:

Originally Posted by Romanator21 (Post 222951)
Mitch, If I'm not mistaken, CoD should implement changing CoG. However, if you look in one youtube video, you can see a Hurricane flying around with only one wing (after hitting a Fiat). Maybe weight distribution is not quite working at this point, or it will be "switched on" at a later point.

http://www.youtube.com/watch?v=bKcL2_-dB0I

(skip to 4:45)

Either bug (unlikely) or very easy settings. Nothing to worry

Skoshi Tiger 02-11-2011 11:04 PM

http://farm4.static.flickr.com/3017/...54e80a49b1.jpg

http://i1042.photobucket.com/albums/...er/spit001.jpg

http://www.militaryimages.net/photop...erbolt_p47.jpg

B25Mitch 02-12-2011 02:49 AM

Note that one side of the landing gear is still intact in the above pictures, and this is appears not to be the case with the screenie of the hurricane in CoD.

Wolf_Rider 02-12-2011 04:19 AM

engines do have a fair weight to them though and can serve as a counterweight depending on how "flattened" the fuselage is

OrangeYoshi 02-12-2011 04:27 AM

Quote:

Originally Posted by Romanator21 (Post 222951)
Mitch, If I'm not mistaken, CoD should implement changing CoG. However, if you look in one youtube video, you can see a Hurricane flying around with only one wing (after hitting a Fiat). Maybe weight distribution is not quite working at this point, or it will be "switched on" at a later point.

http://www.youtube.com/watch?v=bKcL2_-dB0I

(skip to 4:45)

Shouldn't that be possible if enough of the wing is left and the engine is providing enough torque?

Blakduk 02-12-2011 06:11 AM

This video looks more like the game is running on 'indestructible' mode- similar to what happens when you dial down the difficulty levels in IL2. I noticed they were no signs of stalling etc when the pilot was flinging it around. Not a bad idea when doing a demonstration for people.
The internal structure of the wing looks good though.

Romanator21 02-12-2011 08:45 AM

Quote:

Shouldn't that be possible if enough of the wing is left and the engine is providing enough torque?
NO!

(not like in the video - HALF of the right wing is gone, and the engine cannot provide the torque, especially in level flight. You may want to bring up the case of the Israeli F-15, but recall that it goes very fast, the whole fuselage acts like a wing, and roll control is provided by the tail, not by ailerons. In this case, the pilot had full control, and only lost a small part of the effective lift surface. In the Hurricane, as shown here, the imbalance is much greater, the effect of torque is negligible, and roll control is halved. Airplanes can fly with wing surfaces missing, but the circumstances are outstanding.)

Quote:

Either bug (unlikely) or very easy settings. Nothing to worry
I'm not worrying, just pointing out, that it's not necessary to worry about how the plane sits on the ground, when it still doesn't fly perfectly through the air :) If it's a bug it will be sorted.

I'm sure this has come to the attention of the team. Let's wait and see.

EDIT

Quote:

This video looks more like the game is running on 'indestructible' mode- similar to what happens when you dial down the difficulty levels in IL2.
You're probably right - notice the arrows, icons, and unrealistic gunnery (no bullet drop).


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