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PHYSICS Tyres! oh... it's raining...

Discussion in 'ACC Blog' started by Aristotelis, Sep 6, 2018.

  1. I just want to give some Feedback after some more laps in wet conditions:

    In my opinion, ACC has the best and most believeable rain physics on track, i ever experienced in a racing simulation so far!
    And when you hit a puddle...oh no, just don't. :D:eek:

    The FFB works pretty good there too, even, when it's imho a little bit to dampened in dry conditions , but in the wet it's pretty okay.

    I'm a little bit overwhelmed.^^
  2. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    That's the problem actually. Even in the worst raining conditions, driving alone allows you to predict situations. Racing, needs extra movements depending what your opponents do... that adds unpredictability and it's the worse case scenario in heavy rain.
    Fremen_78, Dean Ogurek and D_Rod like this.
  3. Its what separates me from actual racing drivers! (well, one of the many things :D)

    But really I can't get over how great the wet driving is already, even without any of the evolving/dynamic stuff. Easily the highlight of ACC so far for me.
  4. mantasisg

    mantasisg Racer

    The wet driving is for sure the highlight of AC. For sure ! And there even seems not to be too many puddles in the Nurb (but where they are, you get to know them :D), also drying line is not in just yet, as well as dynamic conditions. And most importantly - the alternative racing lines in the way which will just happen naturally when the rubbered smooth tarmac will get wet and provide so much less grip than off line (unless you'll be brave enough to slide through it and hope to grip up, I guess :D). Can you imagine how much more fun it will get ?

    Really love driving in the wet, especially heavy and storm. Heavy rain looks much better than storm because in storm tarmac and gravel traps seems not to be shaded well. But it is storm when the true expected wet driving feel kick in, very very very believable, it really must be spot on, it was true gt3 cars can be very exciting (and with such awesome physics I actually love them in the dry too, really amazing feel, the immersion, the awareness, it is weird how for first hour or two of driving i didn't like it that much as I did later). Love it.

    I'd expect Heavy rain to have significant puddles, much like in the storm, while in the storm I would expect even more rough conditions, or does track collect more water over the time ? But seems quite static in this initial release, I suppose will come with dynamic weather, really can not wait for that.

    Kerbs has surprisingly a lot of grip.

    Tires feel amazing, I feel like they are all so busy in so much different tasks each, they really do lots of stuff, and are so dynamic, really having a feeling being on four wheels. There is so much of play with the car actually, perhaps maybe as much as it would be with some classic car, it all just happens within narrower slip angles and quicker. I also love the significant grip fall-off over the peak, thats something I used to hope. Weirdly in my first hours i didn't enjoy the car too much, felt like peak slip angles are just too small, and you just had no right to play with the car, but it somehow changed rather quickly, and I started really having a blast.

    More about tires. Force feedback is epic ! I suppose it is going to be adjusted, but I hope not much away from how it is now. Using T300 here. FFB feels minimalistic and authentic to me, very clean feel, I don't know if any output details are missing (i suppose probably not, but not sure, thinking about longitudinal weight transfer, but not sure at all). The ffb feels all about front wheels, and it feels awesome. I am not sure if I am right, placebo could be strong, but i suppose there could be little mismatch between peak lateral force and peak self aligning torque, which should be absolutely realistic, and makes you do those famous sawing steering wheel movements as you try to locate the very peak slip angle + catching the slides, balancing front vs rear. Also you kinda feel the rubber lol, you feel like there is tiny delay of wheel to tire patch actions, front vs rear relationships are more pronounced, you feel as the car shifted cm or two because of tires flexing, or rear end starts "swimming" a bit.

    ACC is fantastic achievement right from first day, or second :D I feel weird, but I have to admit that in general the first day I had rather bad first impression, but it was mostly about other things than physics and ffb.
  5. martcerv

    martcerv Alien

    Im fairly sure currently track gets wetter over time, when running light rain puddles were building for me. Quite fun to run slicks in light rain but I was still a bit faster on wets but if track dried a little it would open up the option of dry or wet tyres. A drying track once thats implemented can likely still be much wetter then light rain off line but dryer on.

    Once mp is in I will be running some servers and weather will be variable not always sunny like the majority of servers I suspect will be.
    mms likes this.
  6. claudiopolez

    claudiopolez Simracer

    Will the slippery white-paint lines be simulated? Braking and catching one of them is fun - especially when its wet :) Wet curbs can be trouble too. Not sure if this was asked before...
  7. Dean Ogurek

    Dean Ogurek Alien

    I think one of the most fun parts of rain-driving is when the track begins to dry and running the dry-line becomes the challenge. Going off line can make things interesting quickly and managing grip-levels under changing conditions becomes essential.
  8. Dean Ogurek

    Dean Ogurek Alien

    I lost the rear recently when I hit the painted curbing coming out of a turn in light rain so I suspect that hazard is present in ACC. :)
  9. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Thank you guys for your nice words. We knew the new tyre model is "talking a lot and fast" and also knew the cars are "harder". They need some time, but we were confident that you guys would start to appreciate the results and it is happening.
    As @mantasisg said, of course the peak and re-alignment force have different peaks, but most importantly you can feel the movement of the footprint while it flexes laterally and longitudinally. Pressures and heat also go to influence this, can make a lot of subtle differences on how the tyre reacts and gives back feedback.

    Wet conditions.
    Wet conditions start in a clean track, so you still don't get the rubbered line. Next release hopefully.
    Puddles do form deeper, the more you run under rain conditions, even in this release. But puddles at the real Nurburgring are low in number and in depth. It was actually a decision of big discussion inside Kunos as we wanted to showcase the wet simulation and Nurburgring wasn't the best example. But it was the best choice for the Sim-Expo and final Blancpain sprint race that is happening as we speak. Still it is also a good example that we're not going to overdo an effect just because it's cool. We make them in a realistic manner from circuit to circuit. Some of them have a lot and are dangerous, some of them have much less and have more grip under rain conditions.

    Kerbs have quite less grip, but the good TC is saving you if you drive properly over them. Go over them a bit too "happy" especially with some lateral slip, and you'll be in danger. Still, they should have even less grip and they will, but surprise surprise... the AI can't handle them and it's not easy to make them "understand". But we will get there.

    White lines less grip, unfortunately is not simulated, at least not now
  10. martcerv

    martcerv Alien

    Its good to see this, I know Project cars doesnt go by this logic. They have swimming pools in some corners which just ruins the wet driving experiance with their over used cool effect. Same with the Forza series who like to make rally stage water splashes mid race track. ;)
  11. mantasisg

    mantasisg Racer

    Awesome stuff ! The physics+ffb are really subtle, no doubt, needs a hour or a few to get used and then it feels magic.

    I think I am going right now to do a good 20mins stint in the heavy rain. Nurburgring is so obviously very well designed with rain control in mind :D But the very first day I just kept spinning in the storm, next day was driving consistently. Even though Nurburgring feels relatively safe in the wet, then I reduce TC and ABS, and start driving almost like Kenny Brack drove GT40 in Goodwood Revival lol

    I think Nurburgring and no rubbered lines is actually best for initial release. Starting small and then going big, the best. Many people would be overwhelmed by more puddles I suppose. There are so many people who are giving up so easily on their first impressions, even if thats just them not being used to something. I've experienced that as a modder, and been the one who had wrong first ipression many times as well. Rubbered lines will be "wtf" for so many people, many won't understand whats happening, good not to have it right at the beginning. I hope everyobody will learn it.

    As for wet WHITE lines, I think we should see them how they looks. Wet surface is as dangerous as smooth it is, because when it is smooth there is nothing to break the film of water, and nothing for rubber to hold on. So if the paint is very thin layer, then it probably doesn't break the water film, but if it is thick and goes above tarmac it definitely should be slippery. Also paint, rubber and stuff makes local tarmac suface drainage worse, I think.

    Saw this kool video today. Extreme wet lines. That must be very wide rubber build up in the curves.
    Freddie Seng, RSR2KX and Schnipp like this.
  12. Probably a stupid question, but i noticed that the "ideal pressure" is between low 25 and 26.0. Between those values the middle bar is at the same heigth as the other two. Is it correct to believe that i have more grip between those 2 values or it's not necessarily the rule and tyres with the middle bar higher could produce more grip?
  13. GRFOCO

    GRFOCO Alien

    Hi Aris, thanks for your excellent work, into the sim and here in the forum.

    Sorry to waste your time, but can you explain this a little bit?
    If i choose light rain (the 1st rain's step), lap after lap puddles will form in the track. But until what deep level?
    Can the puddles reach the maximum level even with light rain?
    Or there is a limit which every rain condition can't exceed?

    And same question about general wetness and water level all over the track...
    Last edited: Sep 16, 2018
  14. GRFOCO

    GRFOCO Alien

    Ok, here a little test for you guys…:D
    Related on what Aris said, i've tried to see how visually the track is changing under the rain.

    1ST TEST
    • start 8:00
    • light rain
    • time multiplier 48x
    • end 11:00
    i've make a screen at the start and the the end of the test, just for a comparison. To my eyes, ingame i haven't see any tarmac change, but, surprise, watching the 2 screen there was a little change in the track and some little river was becoming to show.

    So, i've tried the max possible solution to see track changing under the rain.
    Under C:\Program Files (x86)\Steam\SteamApps\common\Assetto Corsa Competizione\AC2\Content\Presets\weatherJson there are the 5 weather preset for this build.
    I've modified the file n°5 (equivalent to storm ingame) just to leave the max rain possible, but have a dry track to the start of the session.

    "ambientTemperature": 14.0,
    "roadTemperature": 15.0,
    "wetLevel": 0.0, (default was 0.8)
    "windSpeed": 0.0,
    "windDirection": 0.0,
    "cloudLevel": 1.0,
    "rainLevel": 1.0

    and this is what happened:

    2ND TEST
    • start 8:00
    • storm (modified)
    • time multiplier 48x
    • end 11:00









    Due to forum's limits, i've upload only 10 screens, obviuosly the step between a screen to another is total smooth ingame.
    To be fair, i don't know if track's change is related to time multiplier or to realtime (you can se booth on the screens), but it doesn't care for now i guess.

    I'm loving this game.
    Last edited: Sep 16, 2018
    chakko, zamex23, mms and 2 others like this.
  15. whereSTheFUhd

    whereSTheFUhd Rookie

    That's typical dynamics of a kart, regardless of the weather (i.e., even in the dry), due to the lack of a differential.
    Retrolux likes this.
  16. chakko

    chakko Alien

    Isn't it funny how people always claim that the DTM, and the cars are "boring"? Nothing boring about that vid. :)

    For anyone interested, here is the full race from Paffett's point of view:

    Watched that yesterday, just grand. :) And also a good indicator on how many different weather and grip situations a driver has to face during a race. He starts with wet tyres (or inter, dunno what DTM has), then switches to slicks, obviously, on his stop, then it starts to rain again, and he has to seriously show some driving skills, to keep the car on the track. Lovely to watch really.

    Assetto Corsa DTM as the next sim after ACC? :D
    baboon and mantasisg like this.
  17. claudiopolez

    claudiopolez Simracer

    Thanks for the answer and hope that "at least not now" will change at a later date :) One would think that they are tiny thing on massive wide track, but actually they always overlap with the racing trajectories and do spice things up no end.
  18. mantasisg

    mantasisg Racer

    Don't plant the wishlisting seed in the very first week of ea release lol

    @Aristotelis Would overinflated tires work better removing the water, and vice versa ? Also would a slick tire perform better in the wet if it was overinflated ? I tried to go with slicks in the storm, then I tried maximum inflation, softest arbs, neutral cambers, car seemed like if it could be faster, but the pace really was pretty much the same, perhaps the car just felt more stable, or placebo. As for wet tires, I tried minimum pressure and wet tires with 29psi felt hardly different than 19psi, I expexted to have much more hazzards with minimal inflation in wet tires.
    chakko likes this.
  19. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    It's a compromise. Sure you might get a bit less acquaplanning, but you get more load sensitivity and so less grip. Also the higher spring rate can make the tyre jump more and that's even worse.
    Schnipp and mantasisg like this.
  20. mantasisg

    mantasisg Racer

    Thanks :) I like trying to understand tires.

    I used to think about load sensitivity, difficult to understand it. But didn't think about it too much for wet surfaces yet. I wonder if it is still as important factor when on the wet tarmac versus how it is on the dry tarmac. I assumed it could work differently, thought that there could be less rubber deformation/strain in the wet due to damping of water and less friction because of lost amount of adhesion.

    I just remember reading that it is advised not to have too low pressures in wet, because water can build up in the middle of the contact patch. Also that it takes tire pressure to bite through the water layer. But I suppose it could be that 19PSI is still good for those tires, as for hydroplaning vs load sensitivity compromise.

    Didn't really think about load sensitivity before, now I will have something to think about.
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