Suspension damping and wheel modelling.

I've driven around here for a while, and read a few of the suspension discussions on this forum.

Now, most of the time the cars drive believeable for the standard of roads we have. But at high speeds the model breaks down, or at least feel unrealistic.

One of the issues is the lack of damping in the suspension model. Now, I don't know if this is a flaw in the actual parameters of the model or if it a flaw in the underlying physics, but under stress, the suspension model does not act in a realistic manner. I think the bouncy issue and the high speed grip issue are interconnected.

I have driven a car with worn bushings and soft suspension in real life, and at speed it feels as floaty as the supercar.

I made a quick video that display the kind of behaviour I am talking about. (still processing at the time of writing, may have to give YT a few minutes)

http://youtu.be/SGTVumYbY1k

 

Man what a imbalance, that could be because of the tires, they aren't perfectly round.

 

My point. So how can the devs claim that their tire physics are the best since sliced bread and that high speed instability is from torque?

 

I was having this discussion since last week, according to the devs the suspension physics are fine, tire grip is the problem.
When I saw your video, I had to make another video to show you what else I had found. I send you the video answer on YT in a few.

 

Uploading a lowspeed video that clearly show just how uneven the tires are, and thus of course will destroy any attempt at tire physics the devs might attempt. Physics might be perfect, but the wheel model makes it irrelevant.

Edit:
Still processing...

http://youtu.be/hxeBG3Ar-eY

 

Of course the wheels are uneven, we still use triangles/polygons.

 

And you still claim that the high speed instability is due to tire grip, when the tires are barely even touching the ground? I'm sorry, but that shows a clear lack of understanding of the fundamentals of rubber to ground physics.

Sad, really, this has so much promise.

 

That's not at all what i'm saying. What i'm saying is that there's no real way of fixing this without putting ridiculous amounts of detail into the wheels or faking the whole thing like other games where vehicles basically hover.

 

So it's better with a game where the cars ACTUALLY hover, is that it? Cause you know that's what they do if you have any grasp of the physics at all....

 

No... you have hovered over my point entirely.

 

Hehe! Good one! :-D

There must be some way to smooth the contact path in the physics, surely? No point tesselating or subdividing the graphical representation, but since the issue really only start to uccur at 40mph in the supercar, even a factor of 2 would increase that frequency so it would start to occur at 80mph. I'd think a 32 segment wheel would be doable?

Anyways, I am stil enjoying my rock-climbing forays where this doesn't matter, but hard surface driving is pointless at this stage.

 

The only way to smooth the wheels out at this stage, as far as i'm aware, is to add more beams and nodes to the tire surface which increase the wheel's weight and thoroughly scrape away FPS. The only way to really have full contact with the ground with the current model would be to reduce the tire pressure significantly, but that's then creating a problem on its own.

 

Okay, it's not only the supercar that's having issues with imbalance of tires.

 

I've actually been having good results using 20 rays on my wheels. It does require retuning the weight and beam valuedls though.

 

This shows very clearly how this works currently.

You see the wheel rotate, slam flat and stop, then flipping over to the next flat bit.

 

Before you start complaining about things like this, claiming to know the perfect answer, maybe you should do some actual testing, making your own tires for a car that ARE perfectly round, and THEN come back and say "look guys, your tires are crap. You simply need more segments, then it's fixed, here, try this tire model I made, you'll see it's perfect".

But you won't be making that conclusion, because I've tried 30-segments wheels on the Bolide a few days ago actually. 2 people tested it and said the steering response was way better, however, the floatyness at high speed was still there, just as much. On top of that, when you take a corner with the old tires, slalom a bit, the tires will take a little while before they actually bite. This STILL happens even with HUGE amounts of friction AND 30-segments. The only things that change by making the tires rounder, is the top speed and the controllability you have once you're already sliding.

So now you should go and apologize that you claimed a bunch of crap like it was fact, even though it was all just a theory which turned out wrong. (Saying that making the wheels even and round would fix everything, even though it really doesn't fix the floatyness).

That said, I can see why you would think that making the tires rounder would fix a lot.

Problem is, making them 30 segments slows the game down a *lot*. I got 1-second-freezing a lot even on Gridmap with those tires.
One big reason the tires act like this is due to resonance. By giving the tires more segments it makes it easier for the tires to resonate at certain speeds(hence why even with the current tires, you'll be spinning at certain speeds, but above and below that it's much more controllable)

There's another thing that's causing an issue here...
According to the devs it's really hard or even impossible to have surface-to-surface collision. Point-to-surface collision is all we have at the moment, but that's obviously not the best way to simulate tires...

Also, you claim that the developers said the tire model was perfect and that torque was causing the instabilities... They never said that so I'm not sure where you're pulling that from?. They said that the spinning out when flooring it from a standstill is caused by torque and people not being able to drive, BUT they also stated themselves that the spinning and floatiness at speed is caused by flaws in the tire model and friction model. And that's true. If you floor a sportscar from a standstill you'd expect it to spin out in real life, it's basic physics: you overload the tires with torque they can't put down so they start sliding. So again, you're stating things that aren't even true.
And again: Maybe you should check your facts with proof before you start acting like a smartass who thinks he knows it all...

 

See the highlights in the quote.

Edit:
Imagine 16, or even 30 of these flatspots.. That's what we are driving at the moment.

https://www.youtube.com/watch?v=__0oJUjE_bQ

 

You do realize that the game is still alpha right? I've seen a lot of people complain about how they couldn't control the bolide because of the tire's or suspension, yet I was able to drive it with a keyboard just fine.

 

I do, which is why I am pointing out flaws in the software. There is a difference between being able to drive it and it behaving correctly. All the cars have the same flaw, which is a shortcoming in the physics engine. Some cars hide the issue better than the Bodine with lower speeds and heavier chassis, but they all do it. In the current version (0.3.01) there is no way around the issue, and the devs have said there is no way to do it without "faking" physics. This "faking" is what all the other sims are doing, btw.

 

Other car sims don't have round tires. They have contact spots at the bottom of the wheels, ie the top of the wheel doesn't even have collision. If you think that's correct with the real world, maybe you should look at a real tire for once and see that the whole thing is touchable, not just the bit that touches the ground...
Maybe you don't realise this, but 30-segment tires act as 60-sided wheels at anything above 5mph. This is because one side of the tire is rotated compared to the other side. We currently have 12-segment wheels, which makes them act like 24 sided wheels.
I can guarantee that even 60 segment-tires will still be floaty as hell. There's litterally ZERO difference in floatiness between 30 or 12 segment tires.

I'm sure you're gonna now claim the following: "omg you're so stupid, the fact that they're rotated is what makes them wobbly left and right and that's what makes them floaty!"... Even if you have 30-segment wheels and put both sides of the tire in the center of the wheel, ie a 0-width, they still float, even though they don't wobble at extremely low speeds. That's a 60-sided circle. Try drawing a 60-sided circle.. You'll see how round that is... In fact, you don't need to draw one. The visual model in-game is 32 sides, and you can already barely tell where the edges are.
If you're really gonna give me crap about "not rounder, ROUND'... Maybe you should look at a real wheel and work in a tire shop for a while(I work in a tire shop since over 3 years). Tires and rims are not perfectly round, unlike what people think. Wheelweights exist to counter the assymetries in mass and to counter the inaccuracies in perfect roundness. Hell, even when your wheels are wobbly as hell on the tire balancer, it's still not gonna make your car float when you drive it, you're just gonna feel a lot of vibration in the steeringwheel and worse performance on a track. In every day driving you're not gonna be spinning out at every corner, even if you have a dented rim that's not gonna happen. You might feel it's a lot less grippy when you're on a racetrack, but the floatiness in BeamNG doesn't just happen when at the edge of traction. It happens always at any time.

I can in fact back this up by a real world experience: I had temporary rims on my car while I was refurbishing my own wheels. The wheels I had on didn't have the right center rings on them, but since I didn't have to use the car much, I didn't bother to get new ones because I don't use my car much anyway.
Unexpectedly, I had to go to the shops at some point, and had to take the highway. My wheels had become very uncentered on the hubs after only a kilometer, and my car was knocking and slapping and it felt very very dangerous indeed, I thought my wheels would come off... However, I still didn't spin my tires or start sliding around like a hovercraft like you claim would happen with not-perfectly-round tires.





On top of that, 30 segment-tires in-game are so soft that you simply cannot feel the not-roundness in them at all.
The segments in a 30-sided wheel in this game aren't ANYTHING like flatspots. Flatspots are as big as the contact patch(which depends on how much the tire compresses under the weight of the car)... Because the tires aren't rigid bodies in this game like they are in other games, they compress under the weight of the car. That means there's always more than a single segment touching the ground(more like 3), meaning that on the part of the tire that touches the ground, there's no angle between the segments at all.

HOWEVER, even with 30 segments(60-sided wheels) the cars are still floaty. Trust me, I tried exactly this 2 days ago, thinking the same exact thing. It doesn't help shit. It's not just low-tire-pressure kind of floating either. If you're driving in a straight line, the tires float across the pavement. Only once you slide more than a certain amount, they realise they're sliding and *then* they grip and leave tiremarks. This is what causes both the tail just waving around and it's what causes the delay in steering(the front tires slide for a little, THEN bite and grip and turn the car).

Ninjahobnob said that the only way to cure it is to reduce the tire pressure. This is simply not true. I've been hooning around litterally yesterday in a Bolide with barely any "air" in the tires. Yes, it's VERY grippy even if you do break it loose, but before you get any tiremarks, it still floats the tail and the steering in a slalom, and again, not the "low-tire-pressure" kind of floating...

If you think the devs ever stated their tire model is absolutely perfect, you can point me to the post and I will admit I was wrong. As far as I know they never ever ever stated ANYWHERE that the tires were perfect, because they to know they're flawed. You simply misunderstood what they said or something. They said the suspension is correct, but the tires cause the issues. I'm also pretty sure they also never stated their model is the only physics based one, because afaik the tire model in Live for Speed is also physics based and not very fake, and I also happen to know that at least one of the developers plays Live for Speed.

You're not backing up your statements with anything, you're solely stating that "the maths support my claim"... What maths? Something you did in your head without testing it in practise? I know your statements make sense, when you think about it, but they simply do not apply either in the game world or in real life. Like I said, go make tires that are a billion nodes around, you'll see they still resonate and float just as much.

Also, telling me I can't contribute to this thread is utter arrogance. Even if I knew nothing about it then I'd still be able to post whatever the hell I want. Problem is, I do know a fair bit about it, considering I work in a tire shop and have done so for over 3 years, like I already stated. On top of that I'm on a game design school and have worked with the similar physics engine in Rigs of Rods for about 2 years and built 2 cars in BeamNG already... Maybe you're the one who only knows about real tires, but doesn't have the slightest clue about how mass-spring physics systems work? Considering you think 30-segments wheels in a soft-body engine actually act like 30-sided cylinders, rather than soft cushions with 30 sides...

Now, if you would excuse me, I'm gonna do some more experimenting to see if I can at all reduce the floatiness, just like I have been doing for the past 3 days with no luck whatsoever.