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Video interview with Aris about ACC physics

Discussion in 'ACC General Discussions' started by deadmeat2k, Sep 12, 2019.

  1. deadmeat2k

    deadmeat2k Racer

    The Sim Channel on YT has posted a really great and interesting interview about the current state and future of certain physics and modelling aspects of ACC. Can really recommend it!

    The recording as such is not good but the discussion is great. I guess he should have asked that loud bald guy standing by just watching and interrupting the interview to do something useful instead at hold the camera for him :D @GamerMuscle

    rycil, A-Jin, uelas_77 and 4 others like this.

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  3. SimGuy_1

    SimGuy_1 Alien

    Nice excellent video.
    I didn't quite catch what aris said at 8:23 maybe you can tell me what was the word ?
    Also wow, i didn't knew that ACC does not have chassis flex still TOP sim though.
  4. fnegroni

    fnegroni Racer

    I think it is pretty blatantly obvious that ACC's modeling of reality is "ahead of the game" so to speak.
    The gameplay needs more work, but these days I only have time for one game, and that game is ACC, because it's the only game where I enjoy the visceral feeling of simracing.
    We just need a wider player base, but for now I am training against the AI and I a finally starting to become competitive online too.
    SimGuy_1, tjr and warth0g like this.
  5. fnegroni

    fnegroni Racer

    At 8:23 I think says, "afterwards, personally I would really like to go back to the damage"
    Which I believe refers to focus on the damage model (collision model was the subject of the previous question, the two are probably related). But I might be wrong.
    SimGuy_1 likes this.
  6. TheBoss

    TheBoss Hardcore Simmer

    Could you make a summary? There are many people who do not understand this language. Thank you.
  7. fnegroni

    fnegroni Racer

    Just a summary or a word by word transcript?
    The latter will take longer but would avoid interpretation.
  8. fnegroni

    fnegroni Racer

    I'm doing a sort of word by word transcript now, should be ready soon. Hopefully will help!
    Racert46 likes this.
  9. fnegroni

    fnegroni Racer

    Part 1: 5 contact points, tyre model and contact patch:
    In: So, I'm here with Aris, Aristotelis Vasilakos
    AV: yeah, that's correct, yes
    In: of Kunos Simulazioni
    AV: and that's correct too
    In: and we are quickly gonna talk about physics right? You recently introduced the new tyre model to ACC, the five point tyre patch model. If I may be specific about the tyre model, I was wondering as we were discussing also in my stream, the issue of skipping those sausage kerbs sometimes. And I was doing my calculations but the one ingredient that was missing was basically the length of the tyre patch, I mean I guess the width is basically the width of the tyre, however...
    AV: Almost, almost
    In: almost, but how long does it extend, because it could be something like this, but it could also be...
    AV: Well, it's about like 10cm or something like that, it's not easy but it is dynamic. First of all you need to understand that you have the tyre modelling of the physics, and then you have the contact points. Those things, so many people in the community are confused about; they are two different things.
    You need the contact points to understand where the tyre is touching and what it's touching. Then you start calculating the actual physics.
    So you have the contact points, but once you have what the contact point is touching, then the actual physics of the tyre model goes in.
    And then it calculates all the forces, the movements, rotation, speed, everything. That is a different thing.
    So the contact point is not the actual contact patch.
    Because even with the old tyre model, you had a contact point, but the contact patch was as big as the tyre [patch should be].
    The problem was when calculating the collision to the ground, we only had one contact point.
    That point would tell us "you are on a flat surface": ok, now we can calculate the contact patch, apply all the physics, torsion, elasticity, everything.
    But that's a different thing.
    So the 'famous' five point contact tyre model, is giving us a better indication of what the tyre is touching. Before we had problems with that.
    In: that was causing harsh jumps when getting onto a kerb. Then you would have spikes and would screw up everything else and send you into a spin
    AV: ...or go into some kind of a rail and stay there.
    In: and that was more of a problem in ACC because of the side flex of the tyre. It wasn't as apparent in AC
    AV: And that's another surprise, sometimes you understand it beforehand, sometimes it develops into a situation you don't want to be in.
    So sometime you try to improve something, and we improved the tyre model, with three-dimensional flex, dampening and everything, which is also dynamic, from the heat, pressure and everything, and then the single point made a mess of it.
    In: So if you wanted to calculate how many physics update steps, we would theoretically to cover every piece of asphalt once, and we can't really do that since it depends also on... I guess with more downforce, the patch grows a little in length because of pressure...
    AV: a little bit, but it's not linear
    In: of course and the tyre won't deform linearly
    AV: Exactly, and also you arrive at a point, it's simulated that when you have a lot of forces, you will arrive at a point that more load will shrink the contact patch, because it deforms so much the tyre.
    The Lamborghini racing team was explaining to me that you could put the rear wing at 20 degrees, and they made their measurements and saw that after 18 degrees, it's not the wing that stalls, it still produces downforce but the tyre can't handle any more, and you gain nothing, you lose grip.
    So 20 degrees of rear wing, you would never use it, but if you did, you would get drag and not more grip.
    In: thank you very much for this in-depth explanation.
    SYBER1AN, sid1965, Pier84 and 8 others like this.
  10. fnegroni

    fnegroni Racer

    Part 2: pressures in 1.0.8

    In: what's next in terms of physics for ACC?
    AV: for the 1.0.8 update, we have redone the pressures in the setup, and how they work.
    The actual physics of pressure is not redone because it works pretty well, but the automatic thing that we needed and we created for the setup, that's not working as we wanted: it's confusing, it doesn't make you understand what you are doing, we wanted to create an automatic thing but we f-d'up.
    So what we do now works like this:
    imagine you have a normal car, and you have a compressor with a pressure gauge, and when you put air in the tyre, you don't care what temperature the tyre is, whether it was in the blanket or if it was cold.
    So you decide for 26 psi: you put just 26 and that's it.
    You go back to the track and if the tyres were in the blankets you will find 26 psi.
    And if the outside temperature changes, that doesn't influence anymore the pressure, because when you put the tyre on the car, that is straight out of the blankets, so it is at 65 'C, and that's it.
    So you don't have to calculate if the weather is hot or if it's cold anymore, you just put the pressure in.
    It's easier by trial and error rather than explaining, sounds complicated, but in the end just put the pressure and go.
    It's mainly a UI change.
    SYBER1AN, Apex Gt, sid1965 and 9 others like this.
  11. fnegroni

    fnegroni Racer

    In: The next topic I have here would be on collision physics, is there anything?
    AV: Right now, no.
    We want to finish some stability, and optimisations overall.
    Afterwards, personally I wouuld really like to go back to the damage and how it's created: right now it's very basic, it came from AC1, it has issues, I'm not happy about it, I don't think anybody is happy about it.
    And it would be nice, once we have a stable platform, to go there and, I'm not saying completely revolutionise, but start making it a little bit more logical.
    In: For me personally it would be nice, when the cars touch, for them to behave like you see on TV, that would be nice, right now it's clunky.
    AV: You always have limitations of network, ping, latency, so you can only arrive up to a point, before you have to start adding fake things like "ghost's ability", that we don't do.
    But I know that other arcade games for example, when you collide with one another, they instantly turn the stability control up, and it's like a magic hand the keeps you on the road.
    This is not inside the code, it would never happen.
    We have limits from the technology: in single player possibly we can improve.
    In: That would be very nice. The one thing that was asked for, way back with AC1, was chassis flex. And you guys gave the community a reason why that's not in AC1: you don't have good data on it, and there were so many different cars in AC1. So what I'm asking about ACC, you have one class of cars, more or less, in the game, so now it seems it is not so far reached to have some kind of flex...
    AV: ok, sorry, sorry to interrupt you, but... (you tube subliminal Advertising here...)
    AV: How can we do serious work with those guys [points at GM]
    AV: Chassis flex!
    In: very quickly, is it coming?
    AV: NO! I'll tell you why, the chassis flex is not one number, you have chassis flex in torsion, you have various degrees of torsion, and then you have chassis flex on the suspension mounting points. Not even the manufacturer knows that probably.
    Then you have chassis flex on the arsm [links?], who knows that?
    There are so many numbers, we don't know how they work, and then we also have another issue, there is vibration stiffness, and they are high frequency, and in a sim you have relatively low frequency, or at least not high enough to also have this.
    So you risk to have lots of oscillations that you can't control specifically, and the end result might not be good.
    Or, you end up doing a very simple chassis flex, that's good for marketing.
    Honestly, we don't have the proper data, and we have many other things that we would like to improve, liek aerodynamics and stuff like that.
    We managed to improve the tyre model, so we are not even considering getting into the chassis flex.
    SYBER1AN, Apex Gt, sid1965 and 14 others like this.
  12. Coanda

    Coanda Alien

    @6:22 Aris - "We f@#ked up mainly.."

    Great to see the man be honest. At least they gave it a crack and tried something new.. It's also nice to see his passion for what he does.. :cool:
    mr Switchblade and deadmeat2k like this.
  13. warth0g

    warth0g Hardcore Simmer

    @fnegroni thats a lot of effort - thank you!
    deadmeat2k likes this.
  14. Psit

    Psit Alien

    "Or, you end up doing a very simple chassis flex, that's good for marketing."

    Shots fired.
  15. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    wow @fnegroni thanks a lot for writing this down.
  16. Pier84

    Pier84 Simracer

  17. kunos

    kunos Alien

    we must be the only game company in the world doing interviews where half of the time is spent on what it's not in the game.
    Apex Gt, deadmeat2k, bgil66 and 11 others like this.
  18. LeDude83

    LeDude83 Alien

    Hahaha I guess you're right. And you know what? You're doing this right. Kunos' level of dedication, permanent strive for improvements and honesty is unmatched. Reflecting on weak points only shows that you're willing to improve and that you're able to deal with criticism. Please never lose that.
  19. kunos

    kunos Alien

    I surely hope so
    LeDude83, Micii1, deadmeat2k and 5 others like this.
  20. Coanda

    Coanda Alien

    it's a good thing.. spoken like true racers at heart, always looking at the weaker points to find those last tenths.. never truly happy whilst in the pursuit of the illusion of perfection.. :)
    deadmeat2k likes this.
  21. [ATF]Shanti

    [ATF]Shanti Simracer

    I like how ACC physics convey how far I am away from perfection, every brake, turn in, mid turn, out on accelerator, always I feel there is more to get out of car and track, the limit is always me

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