Physics The Physics discussion thread

[RC45]

Look...you're wrong. To date, IER has done 6 cars with even more extensive data than what you have access to (regardless of the fact that you physically have the car). One of these cars was tested by a driver that professionally races it in real life (which in and of itself implies a much more in-depth understanding of "feel" than someone that doesn't race) and effectively said that the only difference to real life is that he wasn't sitting in the actual car driving around the actual track (and the brake pedal he was using allowed for more brake pressure than the real thing - so easier to lock the brakes). We're not questioning the accuracy of Kunos' cars...they may not have had enough data and improvised to make the car accurate based on their knowledge. We're arguing for the accuracy of the underlying physics engine, which is undeniably sound.

Uhm - again you are talking about the AS BUILT car - of course it "feels" like the real thing - I long ago stated that very thing.

But if you are telling me that I cannot pull a tire file out and use it as is without tweaks - even where the tire would be EXACTLY the same - I am talking about the digital equivalent of swapping wheels and tires between real cars - then you are actually agreeing with me when I say the engine is using massaged data to get that "real feeling".

Oh and I have read all your posts from 2014/2015 over on the official AC site - you only have this arrogant response each time because you where TOLD all these details early on - well until KS shut the entire place down that is.

As for "access to data" it is not just my car, but rather a pool of about 25 cars that data has been gathered from and averaged out - and with 1000's of laps of track time under my own belt in various cars in real life (many with 600rwhp+ on tap) I am very comfortable with my judgment as to "feel vs real" thank you very much.

 

[David Dominguez]

You shouldn't overestimate what Kunos does. There are some cars that probably have lots of data, and other cars that maybe don't. Maybe the C7 is an example of the latter.

Having said that, they don't make the tires individually, they are generated with a tool based on certain properties, like tyre/rim dimensions, aspect ratio, tread, compound, etc . It doesn't necessary mean that they are a copy of the real ones, basically because it's impossible to have such amount of data from every tyre manufacturer and every car.

 

[mclarenf1papa]

"So you are agreeing then that the AC sim engine needs to each tire tweaked per car even if the tire is the SAME TIRE because the sim engine is not very good?
That's fine - just say that AC needs fudged numbers to work - no shame in that, but don't pretend it all accurate."

No...not at all...I'm saying that Kunos' tires might not be fully accurate, so for your car you may want to adjust them to what you feel is more accurate....the same thing that David's saying.

Well its not easier to reply to but here goes, my reply is underlined below yours.

My most recent post answers to a few of those comments.....as I wrote, with correct data (no, not "fudged" in any way), cars in AC are pretty much as good as it gets for consumer simulations.

Anyway, the pickup points in the car.ini have no effect on the physics whatsoever. They just adjust the ride height that's displayed in the setup menu.

Uhm - again you are talking about the AS BUILT car - of course it "feels" like the real thing - I long ago stated that very thing.
"As built" meaning using real life data with no number "fudging" whatsoever?

But if you are telling me that I cannot pull a tire fil eout and use it as is without tweaks - even where the tire would be EXACTLY the same - then you are actually agreeing with me when I say the engine is using massaged datat to get that "real feeling".
Read David's most recent post.

Oh and I have read all your posts from 2014/2015 over on the official AC site - you only have this arrogant response each time because you where TOLD all these details early on - well until KS shut the entire place down that is.
By who exactly? We started making cars before the official modding tools were even released for AC...over 2 years ago at this point. The devs have helped with really rather little in terms of modding so it's been a long learning process for everyone.

And with this particular thread, it's not arrogance. It's simply my annoyance in you putting the sim immediately at fault because it's not acting how you would expect it to. (even though you have no explanation for why other than that to get correct feel, you have to fudge numbers; that AC is a completely flawed simulation...it's just not true, and I won't argue about that any longer because I'm sure most other people acknowledge AC's validity at this point. What I will do it try and help you make your car more realistic, of course only if you open up to some advice. - like what's already been given about DCAMBER).

As for "access to data" it is not just my car, but rather a pool of about 25 cars that data has been gathered from and averaged out - and with 1000's of laps of track time under my own belt in various cars in real life (many with 600rwhp+ on tap) I am very comfortable with my judgment as to "feel vs real" thank you very much.
Regardless of how many cars data was sampled from, some of the cars we've worked on have had ridiculously extensive data available; stuff that isn't measurable unless days are spent in the wind tunnel or in CFD analysis (just to pick one example). Things like a 400-point aero map for a single car...In AC that can match to within 5% across the board; within just 1% at relevant ride heights.

 

[guidofoc]

delete

 

[themodsquad]

Ever thought of maybe using Pacejka's formula for tires?

 

[AccAkut]

Uhm - again you are talking about the AS BUILT car - of course it "feels" like the real thing - I long ago stated that very thing.

But if you are telling me that I cannot pull a tire file out and use it as is without tweaks - even where the tire would be EXACTLY the same - I am talking about the digital equivalent of swapping wheels and tires between real cars - then you are actually agreeing with me when I say the engine is using massaged data to get that "real feeling".

You mean "exactly the same" as in tires and rims pulled from a fresh C7 put onto your C5 or tires that have the exact same outer dimensions? I don't know which tires the C7 came from factory with, and if there maybe were differences between your domestic market and the version Europe got. I know a little about all the differences possible in belting, compound and profile, even for exact same outer dimensions.

Then again it feels like you argue for argument's sake and cemented your opinion.

If you're really interested in change format your findings and opinions into a nice form, graphs are always great, and post them over in the official forum's Physic bug section.

 

[Stereo]

Ever thought of maybe using Pacejka's formula for tires?

It has no tire wear, tire temperature, combined slip functions in the model, kinda outdated for game terms. Can be useful for real simulators, where pacejka tire data's the only kind you have and you just want to simulate certain things.

 

[RC45]

delete

Yeah - save the amateur psychoanalysis for drinking around a bar with your friends - I have to assume you analyze every person that posts on AC, including Kunos or am I just the lucky one?

 

[RC45]

You shouldn't overestimate what Kunos does. There are some cars that probably have lots of data, and other cars that maybe don't. Maybe the C7 is an example of the latter.

Having said that, they don't make the tires individually, they are generated with a tool based on certain properties, like tyre/rim dimensions, aspect ratio, tread, compound, etc . It doesn't necessary mean that they are a copy of the real ones, basically because it's impossible to have such amount of data from every tyre manufacturer and every car.

Which again means you are agreeing with my initial analysis - data is fudged to get the correct "feel" - because if modders are CHANGING the data Kunos is using or using their own data made up or estimate data in the tire files rather than the generated data you mention then by definition again, data is being fudged to get the right "feel".

 

[David Dominguez]

No, I'm not agreeing with your initial analysis. Tires are generated after analyzing a database of tires they have, and learning what kind of properties they have, and then they generate them as close as the data they have, using the inputs mentioned earlier. That means they make the tyres in an objective way, with the knowledge they have from their the data. Not adjusted "by feeling" as you say.

If you thought that they measured every individual bit of every tyre of the game, then I'm sorry to tell you that they don't. That's partially the reason of why some sim devs went for a physical tyre model, you just can't get enough data for every tyre in the world.

 

[RC45]

You mean "exactly the same" as in tires and rims pulled from a fresh C7 put onto your C5 or tires that have the exact same outer dimensions?

I a not sure how more clear to make it here.

Wheel and tire swapping between Corvette models has been going on for the entire C5/6/7 life cycle. It can be in the form of take offs, as in someone with a C5Z06 buys new wheels and tires in 2001 the day they bought their car ad a C5 Coupe guy says "I want your wheels and tires thanks" - which means the C5 Coupe guy now has 265/45/17 and 295/30/18 on his C5 Coupe instead of 245/45/17 and 275/40/18's - this has been happening all through the life cycle.

At this time I have 2012 C6 GS wheels/tires (new tires) on my car - in the past I had huge race spec tires with 315/30/18s in front and 345/30/18's in the back - it happens a lot.

That is the point of hoping the AC sim engine is a proper modular sim engine so that complete established tire files can be plugged in and the results used as is.

If I tae a set of C6R take off sized tires and put them on a C5 Z06 I should be able to take the C6R tire file that Kunos uses in game and use it AS IS on the C5 to get the feel of a C5 with C6R race wheels and tires - if this is not possible then the AC sim engine is NOT a modular sim engine as is claimed.

Period.

And you know what, I am ok with that - just come clean and say so. That way at the end of th eday we know that the game is more game than sim and everything carries on as per normal.

But the moment you have to TWEAK the tire file to match the car then you are using fudged number by the very nature of the action of tweaking the file for the car.

I am really sorry you guys can't see this simple truth.

I don't know which tires the C7 came from factory with, and if there maybe were differences between your domestic market and the version Europe got. I know a little about all the differences possible in belting, compound and profile, even for exact same outer dimensions.

Then again it feels like you argue for argument's sake and cemented your opinion.

If you're really interested in change format your findings and opinions into a nice form, graphs are always great, and post them over in the official forum's Physic bug section.

I am not interested in assisting Kunos in any way shape or form - I have witnesses how they treat folks on various forums.

 

[David Dominguez]

And what did you expect? Change width and rim dimensions and expect the engine to adjust the tyre properties on the fly?

 

[RC45]

No, I'm not agreeing with your initial analysis. Tires are generated after analyzing a database of tires they have, and learning what kind of properties they have, and then they generate them as close as the data they have, using the inputs mentioned earlier. That means they make the tyres in an objective way, with the knowledge they have from their the data. Not adjusted "by feeling" as you say.

If you thought that they measured every individual bit of every tyre of the game, then I'm sorry to tell you that they don't. That's partially the reason of why some sim devs went for a physical tyre model, you just can't get enough data for every tyre in the world.

Ok - then why am I being told to adjust the tire file "for your car" if not to fudge the numbers to get the right feeling?

.This isn't about wanting every tire to be modeled to perfection, it is about the sim physics engine giving expecting and correct results when moving a tire from 1 car to another - and in fact if it turns out that Kunos are doing EXACTLY what I am trying to do why on earth are all you guys chastising me for doing what the dev is doing?

Unless it turns out the community modders are the ones fudging the numbers as the "tweak" tires per car to get the right feeling.

I get the feeling you guys are now just arguing for the sake of arguing.

Either the sim engine is good enough to use the same tire as-is between cars and the sim engine correctly simulates the chassis model to account for the changes in dynamic behavior of each car that is using the same tire - or it is not. Period.

If its not, just say so.

 

[RC45]

And what did you expect? Change width and rim dimensions and expect the engine to adjust the tyre properties on the fly?

If the sim engine is modeling tires correctly as suggested by the devs then quite frankly yes - but even if it isn't, if the tire is use as-is the least you should get is the correct behavior for that tire with the different chassis without any custom tire tweaks.

Sounds again like you are agreeing with my initial analysis that AC is not quite the sim engine it is claimed to be.

But what would I know, I am just an idiot sim community member (per Kunos analysis) that is doing the 3D work, physics work and sound work on their own.

Happy Friday to you there old chap. The start of another awesome weekend coming up

 

[David Dominguez]

Ok - then why am I being told to adjust the tire file "for your car" if not to fudge the numbers to get the right feeling?

I already told you, but it's like chatting with a wall. Let's try to make it simple, we have 2 things very clear:

1- You have all the data needed for your car
2- We don't know if Kunos had that data for the C7

So your task is to fill what you lack. You said you used the C7 tyres and needed 3.5 camber to match what you think feels right ... well, unless you have proper tyre data, and I bet you don't, what you have to do is to make the adjustments needed to achieve your goal... if all you needed to do is to rise up the camber a bit, it's not like you are that off, isn't it? It's not like the handling is totally off, according to your initial messages. You know that camber adds a bit of extra lateral grip, and a bit higher cornering stiffness, so then just try to tweak those 2 values... add let's say 2% of lateral grip and reduce friction_limit_angle by 0.1 or 0.2, and see how it goes...

 

[Stereo]

If the sim engine is modeling tires correctly as suggested by the devs then quite frankly yes - but even if it isn't, if the tire is use as-is the least you should get is the correct behavior for that tire with the different chassis without any custom tire tweaks.

Tire width is used to draw the skidmarks and determine physically where on the track the tire is for collisions, surface type, etc.
Rim radius is used when you have a flat tire to decide how far the wheel is able to drop.

You should always assume that the tire parameters are as independent as possible - it's actually easier to model a car accurately this way, because if only one thing is wrong, you only change that number, you don't have to change something that affects 5 different things at once. If changing the rim radius affected tire vertical stiffness (which it does) then you type in the new desired stiffness, you don't just fudge the radius number until you get what you want.

 

[RC45]

I already told you, but it's like chatting with a wall. Let's try to make it simple, we have 2 things very clear:

1- You have all the data needed for your car
2- We don't know if Kunos had that data for the C7

So your task is to fill what you lack. You said you used the C7 tyres and needed 3.5 camber to match what you think feels right ... well, unless you have proper tyre data, and I bet you don't, what you have to do is to make the adjustments needed to achieve your goal... if all you needed to do is to rise up the camber a bit, it's not like you are that off, isn't it? It's not like the handling is totally off, according to your initial messages. You know that camber adds a bit of extra lateral grip, and a bit higher cornering stiffness, so then just try to tweak those 2 values... add let's say 2% of lateral grip and reduce friction_limit_angle by 0.1 or 0.2, and see how it goes...

Ok - let me make it even simpler for you then.

Lets assume the tire data for the C7 is not good (which makes no sense - why would Kunos have good tire data for say the Ruf RT12 but bad data for the C7)

If the sim engine is as good as claimed I should be able to take the tire file from (name the car with what you assume has good tire data) and use that tire on the chassis of my choice (that is input with accurate dimensions) and get the correct handling behavior - whether good or bad without tweaking the tire file.

Or are we to now assume that every Kunos tire file is filled with bad data and is nto to be trusted?

What about all the Audi and Lamborghini tires Kunos put in th egame? All bad as well?

My comments and findings are not just in the context of the STOCK C5 Z06 (which runs 265/40/17 and 295/35/18) but for modded cars as well - see the very point of a broad C5 mod is that the tuned/modded cars will be using a myriad of large tire sizes, mostly in C6Z06/C6ZR1/C7Z06 sizings and some times beyond. For my early testing I used the C7 Stingray tires in the C7 Stingray sizes (which is under tired for what I want but a good yard stick to use none the less)

And for track C5'z those tire sizes are often similar or the same as some other race car tires - they will be Goodyear, Michelin and Hoosier slicks that are already modeled in some n-game race cars - and it would make logical sense to use those tires as is since in real life you are using those very same tires AS IS.

So again, if the engine was up to the task then you should just be able to plug the existing tires into the cars.

But you guys keep going on and on about tweaking the tires per car (maybe even per corner - I don't know how much fudging you guys end up doing) to get the right feel, ok so be it - tires now need to be tweaked "per car" to get the right feel - but if I am using the same Michelin tire on a Corvette track car in a square setup on all 4 corners that say a Porsche Cup car is using on the rear - 300/18, then if the tire is already modeled in the game I should be able to use that same tire as-is.

But I am told this is not so as the engine cant handle it - so I am off to fudge the numbers to get the feeing right

 

[Eduard Mallorquí]

You are trying to make cheese on a toaster, it's just not going to work. Use rF2 or Modelica for proper physics simulation.

 

[David Dominguez]

Well, I'm willing to help people who wants help. You either don't read or you just have your agenda and you don't want to move from your position. I'm not going to repeat myself for the third time, good luck with whatever you want to achieve.

 

[RC45]

(I made this a separate post rather than an edit to the above post)

To be clear, I am not averse to editing tires and making up my OWN tires as I go along - but the idea/hope was that
a) the Kunos data was a better more real starting point (now come to find out its bogus and should be changed forth with )
b) the tires included in the mod that will claim to be "like Hoosier slicks" or "like Michelin Sport Cup" or "like Goodyear slicks" would be closely modeled on what was hoped to be actual "race slick tyres" - again sourced from the devs cars for realism sake
c) picking and choosing different wheel and tire sets by way of configs would allow players to set up their street C5 for track work with appropriate tires selected and get the correct handling (for better or worse) simply based on the tires they choose.

This would allow a player to say, select Hoosier slicks but not upgrade the suspension and get what ever they get handling wise good or bad - versus picking Hoosier slicks AND coil over upgrades and get better results and then later adding the functional front and rear aero elements to get even better results - but it appears the AC engine does not support car changes in this way and is more geared towards a hard coded per car fudged/tweaked setup rather than an ad-hoc setup using configs from a pick list.

You know, the way the rF1 and rF2 engine can

And in real life may of us do have Corvettes we have modded from stock cars to full on track cars with functional aero front and rear, huge brakes and wide sticky rubber - so we do know what the progression feels like - from stock car to all out time attack and everything in between.

That is what I was hoping AC could be used for.

But it appears not - so the mod will just have to have preset per car setups tweaked one by one to get the "right feel".

This above revelation is the primary disappointment - the expectation was that AC was going to be the go-to-sim-engine for the mod in the original form it was imagined.

Mostly because visually AC seems better than rF2 with its very realistic looking shaders etc. and there are a number of prebuilt tools to aid in the testing of the mod over its dev life cycle - this would make for an overall more appealing mod that was easier to build by the current Modding Team - i.e. me - this is a single person effort by the way

The run-time car modding by way of setup pick lists would have been an added bonus - but it appears its not going to work that way - which is a pity because now the player cant mod their car with way they might want to - they will be stuck with cars pre-modded a certain way.