Physics discussion thread

When I look elsewhere, I see people parrotting those "physics are off" claims, but hardly ever going to detail on what way and providing solid arguments and proof. Then those claims would actually be useful. A lot of them are also based on very little personal experience in both game or IRL.

As for IRL drivers, there are very few known names that I have read and made reviews of AMS2 (sim/irl racers like Baldwin, Broadbent, Jardier... who else?). Please provide more? As far as I know, Morad or Perel hasn't yet made a video / review of AMS2 at least. Because the game doesn't have any profilic MP competion scene (and physics definitely hasn't been main reason for that, the MP functionality wasn't even close to being solid enough for it in the past), so it doesn't interest that many as much as the other, bigger titles.

This is not a defence of AMS2 physics, it's annoying as hell to refer to read those claims that doesn't have any substance.

As for other sims feeling similar, ACC and LMU for sure doesn't feel similar with the GT3. Other sims definitely don't have perfect physics either, ACC with it's suspension implementation is a good example of that (and braking). Both of those games have plenty of weird things going on with how you can and should set the setup for optimal performance, which to me always mean that the simulation isn't perfect there either. For sure, AMS2 haven't had all things correct, still doesn't and never will, just like every other sim, but probably because some of the bigger problems in the past (originating from project cars), it got famous having "imperfect physics" and that stick to this day (unlike other sims), no matter how much those have improved.

1.6.8 improvement with the GT3's was clear, it definitely removed the rear coming too lose easily on corner entry, especially if trail braking deeper into the corner and reduced the on throttle rotation tendencies a bit. I did back to back comparison testing with this during beta phase between previous public release, so it wasn't placebo. For those whom these issues were the main problem, the change was really significant, but if you had some other issues with the simulation, it's understandable that such person might not feel that way.

I do see imperfections with the GT3's and how driving them feel in AMS2, not feeling heavy as if there wouldn't be enough forces pushing the whole car in corners, tires not being peaky with grip dropoff, maybe having too much downforce in the rear etc. But in similar way, I feel imperfections in all the other sims I have tried GT3's as well, just different kind.

 

You're reading a bit too much into my post I think. I'm not a fanboy and I wouldn't defend any point I don't like about a game just because. I also spend my time in other sims, and not in AMS2 only.

If you check my post history I think 1.6.5 already updated GT3s so much, that I couldn't find that much difference to LMU especially on cars like the M4 GT3. 1.6.7 was the biggest step since then with the adjustment of rear aero loss on yaw rotation. Jumping between LMU und AMS2 GT3s is to me as close to each other as any other sim.

With 1.6.8 I even ran into the issue that I couldn't drive GT3s anymore since they constantly understeered, until I switched back to Default FFB and that solved all the issues. So I'm totally open to talk about issues when I encounter them.

So with that being said, I actually just want to help solve issues of people still saying they feel the cars slide since I absolutely can't feel or see that in my rig. But for this we need to dig deeper than just the typical "it's still slidy" post, that can't show any gameplay clip that showcases where the slip happens so other could recreate the issue and test if the same things happens to them. Especially since n off FFB can easily give wrong impressions of how much grip a car has (and I even had this issue with Custom FFB in 1.6.8). Or even better capture telemetry like Peter Stefani does here to point out anomalies.

 

Aren’t the bump stops only on compression? The issue on the RSR is during Extention of the suspension upwards upon braking.

Almost as if the top of springs are not attached to the body of the car, as a manner of speaking. Probably would be impossible in practice, but in the end this is just a simulation, not real hardware. I guess anything can happen when it’s all just code and formulas.
And if you look at some other cars where you can visually see the rear suspension in action, you don’t see this extreme Extentions, and it doesn’t appear as anything odd in the MoTeC readings either.
You can see the rear suspension moving up on braking, but not to the point where it just flat lines and sits there.
I really should look at that other Porsche that is similar, and how it responds under braking. Then report back about it.

 

This would be useful to remember for all of us here. Errors can be overlooked when things seem fine on the surface or during test drives.

I think there is clearly enough evidence here that Reiza should investigate the issue (telemetry error only or a modelling error leading to telemetry wonkiness) with this car. Just in case they are not paying attention (due to busy release schedule and dealing with all sorts of issues with new stuff), I will add it to their list The car is way too much fun to drive now to leave it with an unaddressed problem.

 

I drove the car and agree with you that there's something wrong with the bump stops. And this is just my opinion, but I think this car should understeer more when braking.

 

Yeah we tried with full bump stops and no bump stops, did not make any noticeable differences. And to be clear, the issue is NOT about the bump stops.
If the investigation gets done, it would likely result in an increase in the spring ranges.
I’ll be checking the other Porsche later today to see what is modeled in that car and how it performs.

 

For me when it comes to GT3, LMU is my favourite

Yea the likes of LMU do them better, where they require precision and you have to be more careful as it’s much easier to make a mistake.
Where’s in ams2 the slidy behaviour is mostly gone, but you can be much more aggressive and less precise in your inputs.
It’s as though you have way more grip and downforce, but for me they feel much improved than earlier and now at least fun to drive, but ultimately it would be nice to have to require more precision, and balance in inputs overall and bring them closer to other sims.

but overall it’s now getting to a state where if the career mode is really good, I will put some serious time into AMS 2.

 

Never

 

You have to be very precise when you want to be fast. If you overdrive the car you will lose a lot of time. The big difference is that you don't lose the car to uncatchable snap oversteer when overdriving the car or randomly in certain corners, so you aren't enforced to underdrive the car all the time when pushing them to the limit.

As showcased in other posts with tons of IMSA clips, IMSA GT3s are quite loose on the rear when driven hard and don't spin out instantly when rear grip is fading. I get that people are used to this underdriving approach and like it, but I honestly hope AMS2 does not take that as a target.

 

The other 911 Cup cars 3.8 and 4.0 (even though different from the 1974 RSR) didn't show anything odd and drove well.
One thing we noticed was that the 74 RSR had quite a bit higher ride height values than the other Cup cars, GT3, and GTE.

 

Wet weather physics

Physics in sim racing is a very hotly debated manner with lots of differing opinions. But if there is one thing that is unanimously agreed on among real life drivers, it's the fact that iRacing has the best wet weather model. The reason for this is that iRacing is the only sim that has a really good implementation of the slipperiness of the rubbered dry line in the wet. In all other sims you can pretty much just copy your dry line into the wet without having to think about staying off the rubbered line. And unfortunately, this also includes ams2.
I know that ams2 has some sort of grip reduction on the rubbered line already - this was mentioned in multiple dev updates. But it's definitely not quite there yet. The diffrence in grip is hardly noticable. When you look at real life onboard footages of cars going onto the dry line in the wet, you can immediately see how slippery the dry line is and how the cars immediately start sliding around.
For example here:

And ams2 doesn't give you this kind of sensation at all. The car doesn't feel much different, no matter if it is on the rubbered line or not.

I recently made a test, where i compared taking the dry line versus taking the wet line in the wet and it became clear that taking the dry line is still the fastest way to drive in the wet in ams2.
My full test:

I know how much the devs care about this title and would love to see the wet weather physics getting a little bit more attention. And hopefully we'll get an actual wet line in ams2 in the future

 

without having time to watch vid , so don’t know if you touch on it.
But was the track state rubbered in ?
Because it’s quite noticeable when the track has been rubbered in .

 

Other sims should not be the benchmark, real life should be the benchmark where possible.

 

Yes, but other sims are closer. At the end of the day day, it’s about fun, and AMS 2 is a fantastic all around package, but it’ll never be the next big thing in sim racing for a lot of people because of how some of the physics ect behave.
It’s at a point now where i will play a little most weeks, and I hope that how some of the cars handle and feel can continued to be improved even more going forward.

 

Prove it with real life telemetry against sim telemetry.

 

Can we flip the burden of proof before we continue this discussion? Seydlitz showed one example where the wet line is not faster than the rubbered line. For us to have something to discuss, we need evidence that the opposite can also be true - that the wet line can indeed be faster than the rubbered line.

Reiza has provided evidence that the rubbered line becomes slippery, at 1m31s in this video:

…but what I haven't seen evidence of, is that it's faster to use the wet line.

Speaking from my own experience of real life rental karting in the rain, it's quite possible for someone to pass on the outside of a hairpin while the person on the inside has to slow down to a crawl to maintain grip on the rubbered line. It can be several seconds of laptime faster to use the wet line, if the track is properly rubbered, flat, and soaked. I have yet to experience the same in AMS2, in fact I have yet to experience that the wet line is faster at all. The wet line feels more grippy in the FFB, but it's always slower for me.

Normally, I would use karts in AMS2 to do such testing, but the problem with karts and kart tracks in this case is that even in a 30-minute session when I'm the only one on the track, the LiveTrack-generated rubbered line covers as much as 3/4 of the track width, so it gets really difficult to find a wet line at all. The problem with high-downforce cars such as in the Reiza video clip above is that the high downforce compensates for some of the grip loss, so the effect may be smaller than with karts or road cars. I'm basically asking for someone to give me detailed instructinos for how to reproduce that the wet line is faster.

 

Of course first would be important to define a section where taking wet line should be faster IRL than more slippery rubbered line. It's not like it's the whole lap where you avoid driving the rubbered line on wet (and how wet it should be when it makes a difference).

From my personal experience, if the track is well rubbered before getting wet, you can notice the better traction for corner exits and it feels beneficial if there is a decent straight afterwards. On corners, it might be often best to do the normal racing line even if there less grip.

Could be also that there is less difference because it's been hard to tune AI if the impact would be a lot bigger (one of the reasons why you had too much grip easily on wet).

One thing that can also impact the test results, is the track surface temperatures. At least in the past, you could have maybe too much grip on wet with slick if you just were able to keep the tires in good temperatures. If it's not slippery enough, the impact of having more grip outside rubbered line will be less meaningful and you probably lose more time by not using all the track.

ps. I don't play iRacing, so I can't be sure how it's there, but I wouldn't be surprised if the impact is there obvious and even stronger than IRL (I know that the marbles build up visually is at least over the top compared reality based on comments from people like James Baldwin)

 

I remember testing the FF1600 in iRacing at Brands Indy in the rain, and the difference between wet and rubbered line was noticeable and felt very familiar to real life, but I don't think it was as much of a difference between wet/rubbered line in iRacing as what I remember from karting in the rain IRL. Maybe they've toned it down a little.

 

I had forgotten that there was a video not too far in the past that actually tested this dry vs wet line thing in AMS2

(I do recommend the whole video, not just this part!)

I REALLY recommend also watching other AMS2 related videos from this channel, more than worth the time spent because they really highlight a lot of the positives of physics simulation on AMS2. There videos about bump stops, dampers, rolling resistance etc. (and good content for other sims too).

AMS2 physics might not always be perfect (same with other sims), but there are plenty of positives too on that front, where it might be even best of the current sims.

ps. the channel uses AI dubbing, but is not AI generated content otherwise!

 

I think, based on Max Verstappen's performance in the famous Brazil 2024 GP, it seems like turn 3 at Interlagos might be a good testing ground - he famously passed several cars just going round the outside.

Thinking about it, a 'rain' TT mode, if possible, would solve the problem for us. We can just Monte Carlo the optimal way to drive; if the wet line isn't faster, you'll see it in the ghosts.