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PHYSICS ACC V1.6 improved tyre model and DHE 2020 compound!

Discussion in 'ACC Blog' started by Aristotelis, Nov 18, 2020.

  1. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Improvements in the current tyre model.

    Improvements in the realignment forces
    Research and better data resulted in an improved simulation in the generation and scaling of tyre-realignment forces and their relative influence on tyre grip. The improved tyre model remains more constant in over- and around-the-limit grip, as it is influenced by the realignment forces to a lesser degree. Still, the resulting forces pass through the suspension geometry, which creates a leverage of finally feeding into the steering wheel. We believe that the end result is more communicative FFB and better response of tyre grip.

    In close-to-limit situations and especially transition situations such as chicanes or light-load scenarios, when the grip decreases to levels that were making the realignment forces more prominent, the behaviour is now more stable. Mid-engined cars, such as the Lamborghini and Audi, and the Porsche should showcase improved stability in such scenarios. Those cars are by design extremely agile, but can also become unstable in fast direction changes and therefore ask for precise inputs. Now they can be driven more aggressively and have increased ability to change lines while on and around the limit. They should also feel more stable in turn in under trail-braking conditions even on crests and downhill sections, reducing or even eliminating the undesired "oversteer when releasing the brakes" effect that had a tendency to happen before.

    Obviously, all of the above has an effect on the force feedback, and we think that it’s now even more communicative. That extra communication from the FFB might give the impression of a more edgy tyre, while in reality the grip is stable, which is the reason why the tyres are more responsive around the limit. Try to trust the tyre and see what happens. We are confident that after a bit of practice you will notice and take advantage of the improved feel.


    Pressure influence on the footprint area and rolling resistance.
    Further improvements have been made in the simulation of pressure dependency and its effects on the tyre footprint and resulting grip. Tyres are now more sensitive to pressure, and you will feel the tyres providing less grip at below and over optimum pressures. We strongly advice to take your time heating up the tyres in the first couple of laps and you should be able to notice even more your steering wheel FFB getting heavier while the pressure and heat builds up. A clear indication that you can start pushing the car and tyres more.

    As always, tyre pressure also affects rolling resistance. The more pressure you have on your tyres, the less rolling resistance you will get and vice versa. Now on version 1.6, the simulation is more accurate and the improvement in rolling resistance with more tyre pressure is not strictly linear. Setup exploits from very fast drivers that used higher than ideal pressure to gain better acceleration and top speed are not so effective anymore, as the tyres will lose quite a bit of footprint and will result in lower grip under braking, cornering and traction without gaining much acceleration and top speed.

    All the improvements described above affect all the tyre variants in ACC, but obviously to a different extent for each tyre.


    The Pirelli DHE 2020 tyre compound
    (available in the 2020 GT World Challenge Pack DLC)

    Finally, the 2020 season brings a brand new Pirelli tyre compound, called DHE.
    Improving the DHD2 tyre is not an easy task. The old tyre might not have been an absolute monster in terms of grip, but it was amazingly adaptable to any kind of weather condition, track surface, engine power delivery and car layout, while sustaining over 1500kg of weight and 600kg of downforce at the same time. All of it with a single compound that, if handled with care, could make it through double driver stints exceeding a total of 2 hours.

    The new DHE manages to improve all the above characteristics and more. The DHE compound improves lateral support and traction at the rear. Sidewall stiffness is higher, allowing improved control of the aerodynamic platform even at higher loads and speeds. The tyre also suffers less overheating under heavy loads, resulting in more stable grip even on cars with high BOP ballast loads.
    Further important improvements can be found in tyre wear. The DHE compound can deliver more stable grip during a whole 60-minute driver stint, can sustain double stints better, and exhibits a less pronounced transition from the initial "qualifying" grip. This permits more aggressive setups without significant compromises for the race, especially on cars with more rear weight bias.
    Ideal pressure remains in a window of 27.3 to 27.9psi

    All in all, while the new DHE compound might not give better absolute grip values, its characteristics allow for less compromise in the setups, more on-the-limit driving and improved control of the aerodynamic platform, which translates in better performance. If not for the single hotlap, certainly for a full race stint.

    DHE tyres are available on European tracks when played through the 2020 season:
    Monza, Brands Hatch, Silverstone, Paul Ricard, Misano, Zandvoort, Spa, Nurburgring, Hungaroring, Barcelona, Imola and Zolder.
    In Multiplayer, these tracks have to be set with the "_2020" suffix in the server event settings to achieve the same result.

    The 2020 season featuring the DHE tyres is playable without owning the DLC, what the DLC gives you access to is Imola and the two new evo cars. This means that when you pick the 2020 season in the main UI, you get the DHE tyres for base game content, and the same happens when joining 2020 track servers.

    IGT tracks do not (yet) have a 2020 BOP available with DHE tyres, they fall back to their original 2019 BOP regardless of which season they are played through. Accordingly, IGT tracks also do not have a 2020 server version.

    We hope you will enjoy the new tyre model and new tyre compound in Assetto Corsa Competizione v1.6 and the 2020 GT World Challenge DLC Pack!
     
    Last edited by a moderator: Nov 19, 2020

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  3. Dewald Nel

    Dewald Nel Racer

    Literally watching you explain this in your video right now.

    Can't wait to try it.
     
    AndyK70 and sissydriver like this.
  4. While the Lord of physics is in the house :) I'll try to get a answer here.
    I'm full of understanding if my question is ignored at the release day. And the days after. :p
     
    romandevision likes this.
  5. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Tyre walls stiffness and rotational speed expansion has been part since AC1. ACC goes even further by simulating physical three dimensional flex (instead of just vertical and mathematical lateral). On top of that all the equations are influenced by load, heat, pressure, surface, wetness, wear, tearing, blistering and graining which then not only just modifies the grip of the tyre but also and more importantly the flexibility, damping, stiffness and peak slip angles and ratios. All in real time all dynamically interacting obviously.

    I still don't understand though why we need to lose time with an ignorant troll attacks.
    On the other hand, trying to understand what pushes some people to claim and attack a simulator physics engine inner workings with no inside information whatsoever (or even worse, false information), while at the same time having no real knowledge of how vehicle and simulation physics work... well that is beyond me. If it's because of simple preference and hate, then it needs an expert medical professional advice.
     
    menos | M6, Obrom, ocin and 22 others like this.
  6. AndyK70

    AndyK70 Hardcore Simmer

    @After_Midnight The answer is in the post, isn't it?
    Regarding the new 2020 DHE tire Aris said:
    So the answer is: The tire walls are part of the simulation.
    At what percentage? Err... I don't understand the question. I would assume the sidewall is part of the equations where it matters.


    edit: Well I was a minute late, Aris answered it. :D
     
    sissydriver and After_Midnight like this.
  7. Thank you very very much. I don't understand the attacks against Kunos as well. And arguing leads to nothing most of the time without validated informations. :rolleyes:

    It was meant as a question how important the tire walls are for the simulation of the behaviour of a real tire. :)
     
  8. sissydriver

    sissydriver Alien

    ninja'ed by aris. could be worse :D
     
    AndyK70 and After_Midnight like this.
  9. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Well that is a question that can lead to a veeeery long discussion. But i'll try to be short and to the point.
    As the simulation of tyres and vehicles evolves, we slowly moved from the idea of "tyre model choice and grip curves are the most important things to a simulation" to a much more refined and full of small details understanding and development.
    Tyre models are now quite well known. You choose one, you use it, you know what to expect (more or less). The problem is, what data you feed in it and how and what extra features you can add to it. Because the usual tyre models available from scientific papers and books, at least the real time ones out there, are made to describe a tyre behaviour in generic and well specified conditions. With certain accuracy and fidelity, but still... generic.
    Incredibly enough our "niche videogames" now need much more features in the tyre model than what a normal tyre model can provide. So you need to be able to add feature to it. Heating, wear, damage, different surfaces, wetness, aquaplaning, external factors that influence it (like brake heat) etc etc. All factors that a normal tyre model doesn't really care to describe.
    So you end up with a tyre model with hundreds and hundreds of values... and some (many?) of them might not even known with exact precision. So experimentation, reverse engineering, telemetry studies and, of course, personal feel and experience. Sometimes you end up changing 2 or 3 values of the hundreds, and you change them by an insignificant % different... and yet you feel a good improvement. The telemetry is more accurate. You release it and people fall in love of it, or hate it. And you still trying to find out why this tiny difference made all the difference for the drivers. On the other hand, you might change a ton of values and people won't even appreciate it because it fits your data, but doesn't really change the feel of the tyre except maybe in some extreme situations.

    So yeah nowadays everything is important to simulate the behaviour of a real tyre, even the most tiny and insignificant value changes.

    edit: by "we" I mean not just kunos but pretty much every advanced simracing developer out there.
     
    menos | M6, Dookie, ocin and 13 others like this.
  10. unknwn

    unknwn Alien

    I would guess that the troll in question meant the ability for sidewalls to act as a contact patch. If I remember correctly in AC the cars couldn't roll over (as soon as you reach an angle which would require for the sidewalls to grip the surface you would loose grip and the car would unroll itself).
     
  11. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    cars in AC can rollover. It's all down to the values you put in the tyres. Obviously if you're expecting a Porsche 911 to rollover with a low CoG, then that won't happen easily or at all.
     
    AndyK70 and After_Midnight like this.
  12. unknwn

    unknwn Alien

    I am aware that some cars could roll over very easily such as Reliant Robin 3. However I do remember discussions where people were questioning why more "regular" cars (not GT3 or anything similar) after jumping over the high curbs and reaching high roll angles would unroll instead of driving on 2 wheels and rolling over.:)
     
  13. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Again almost 99% of the cars would not roll even in real life. The little old abarth would rollover probably, but it was a compromise decision because if it would rollover for the player, we saw that then the AI would rollover often and that would have perceived as a bug. But it's all down to a couple of values that control the grip of the tyre at big cambers.

    Saying that sidewalls are not simulated and such, because no rollover, showcases how little he knows about tyre modelling and physics. He still can't separate the graphics from the mathematical model and real object shapes
     
    rdmracer, AndyK70, kamkie and 3 others like this.
  14. Gopher04

    Gopher04 Simracer

    Do we need to make any adjustments to our setup for the improvements in the current tyre model?
     
  15. Radfahrer

    Radfahrer Hardcore Simmer

    #The Newton-ian school of doing things right ^^
    <3

    You can bet on your last slicks on that
     
    AndyK70 likes this.
  16. @Aristotelis Thanks again :) Thank you very much.
    I love the way you're able to communicate things like tires, aero etc. It's understandable even for guys like me without a degree in rocket science.
    You do it in your streams on Youtube, too. And all is provided with pure passion.
    Congratulation for hitting the 20k subs. Well deserved.

    I don't think so. If you have to read a lot of his comments the Dunning-Kruger effect should be come in mind ;)
     
    J.Osap and AndyK70 like this.
  17. unknwn

    unknwn Alien

    I really don't but I do remember some of his cringe ramblings from years back that simracing is arcade. :D

    Anyways it's great to see Kunos continuously working and improving their products.
     
  18. AurusCE

    AurusCE Racer

    @Aristotelis Do all 2020 Cars have the new Pirelli DHE? I'm really sorry if this have already been answered.
     
  19. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    You go into the 2020 season or a multiplayer 2020 circuit... you get automatically the DHE tyre on all European tracks (EDIT: except for IGT tracks, which only have the existing, 2019 BoP with DHD2 tyres, regardless of which season they are played through). You go out in a different season/circuit year... you get the older DHD2 tyre on European tracks as well.
     
    Last edited by a moderator: Nov 18, 2020
    AurusCE likes this.
  20. FrazzleDazle

    FrazzleDazle Rookie

    Amazing work
     
  21. SimGuy_1

    SimGuy_1 Alien

    Amazing tyre physics, wow. GT3 cars in this game feels completely different than any other sims i play.
     

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