Car slipping / turning at 65 mph and above

#1 You'll need to change these parameters in WheeledVehicleTire datablock:
staticFriction
kineticFriction

Increase the values and you'll get less slippage, set it closer to zero and more slippage.

Akio
www.inoculousgames.com

#2 @Akio
That was one of the values i was also messing with to get it to act better.
No matter what i set them too i still get the same reaction out of the car.

But it does help the car turn better at a higher speed.

#3 Car physics in torque is a major issue. One thing to do is make sure the mass is put low on the car, or even under it.

#4 Ah perhaps i should mention im using version 1.3
and starter.racing. Then i made the flat terrain and moddified the speed of the buggy.

*EDIT
I just tried another car i found "tooncar"
That manages to hit ~55 before it wipes out.
Im not using its scripts just the dts file. So maybe it is where the mass is sitting, ill try adjusting that and see what happens.

#5 Chaz,

What friction values are you using?

I'm also using v1.3.

#6 My bugs in my game is nearing ~300 mph with boost, and the high-end bugs can take corners very well even at those speeds.

#7 I just tried it on a clean version (deleted my dir and copied a brand new 1.3 over to it)

The default value for static is 4 and kinetic is 1.25
I increased the staic to 20 and it hits around 80 before it starts slipping.

What values do you use?

#8 Ah ha
i just noticed the higher i set the kinetic value the lower the speed it is before it starts to want to start slip.

#9 Try setting your kinectic friction little higher and it should work ok.

#10 Oh man lol
im so confused right now
now i changed max speed to 300 and left the default values for everything else, it does not want to slip at all. But it does get a lil funky if you let go of the gas or brake. Im just gonna mess with the values a lil by a lil from now on.

But how would you get the car to turn better at higer speeds?

#11 Don't forget about the longitudinal and lateral forces on the wheels. They're going to affect your tires' grip more than anything. The lateral forces affect the tires grip during turning and the longitudinal forces affect acceleration and braking in a straight line. Make sure to adjust the damping for those forces as well, if you adjust your force too high above your damping you'll get a car that seems to be driving on Jello!

Another thing that can help was suggested byCameron above and that is to lower your vehicle's center of mass. The third value in the centerOfMass variable moves the mass on the z axis (up and down). That variable works in torque units, so depending on the scale of your car, it may not take a very large value to move the mass where you want it (my vehicles have the center of mass set at "0 0 -0.2"). You can also change the center of mass by moving the "mass" node in the car's model itself and re-exporting the .dts.

Adjusting the car physics variables is tricky work, there are a lot of variables working together and changing just one typically requires changing a few others as well. You just have to keep tweaking endlessly to get something that works the way you want.

#12 I don't know if this post is outdated now, but after playing with the numbers I found the best control of the car happens when you set it to front wheel drive, kineticfriction = 12 and staticfriction =3.75... at high speeds the vehicle will roll once in a while, if the friction values are set higher, roll overs are more common.

#13 I had a car script with the mass set to something like "0 -0.5 0". That puts the mass a little behind the center of of the car, like in the passenger seat. I found it hard to control that way because it would fishtail at speed. I changed it to "0 0 -1.0" and I much prefer it. That fixed the fishtailing, and it put the center of gravity low (probably a meter below the stick shift) so that the car recovers from rolls quickly. If you want rolls, "0 0 0" would probably do it for you.

-Spencer

#14 Playing around with the kinetic and static friction today and found that Kinetic Friction is the major variable concerning turning response in a vehicle, I found it best set at around 2... the staticFriction seams to deal more with the tires ability to stick/respond to the terrain, found this best set at 4.5..... my vehicle speed with these settings is only 35

#15 @Spencer
I tried out changing the centre of mass with the 0 0 -1 and found that this setting makes it much easier to roll your car, and if trying to correct it with a weapon that has an impulse it is very difficult to roll back over, so I set it at 0 0 -0.5 and it is very hard to roll the car now.
thanks for the advice

#16 @Lyle

I actually ended up changing the numbers on mine, too. I ended up with 0 -0.1 0, not so different from yours. I changed the third number back to 0 because I found -1 made it possible to climb the steepest cliff :). I'm surprised to hear that 0 0 -1 made your car roll over more easily, but this stuff is still pretty mysterious to me.

On the subject of friction, do you understand how kinetic friction differs from lateral and longitudinal force? I find if I lower the lateral force it starts to get squirrelly in much the same way as it does when I lower the friction. In general, do you understand what those "force" values mean?

-Spencer

#17 I hate to sound stupid here, but could you guys post a complete example of a working tire configuration? I tried all the ones listed here, and I either get something that slides all over the track, or something that cannot turn at all.

I would post mine, but I've been changing it so often, I don't think it would help.
I'm just looking for the following data from a working model:

staticFriction
kineticFriction

lateralForce
lateralDamping
lateralRelaxation

longitudinalForce
longitudinalDamping
longitudinalRelaxation

#18
First off, this website is lame that when you type a post and then you check the email notification box, it resets everything that you wrote.


Secondly, did anyone ever figure out the solution to this problem?

I'm developing my own racing game using TSE and I'm suffering the same effects you guys are. When the car is moving slowly, the game seems to run okay, but when you go faster, the car begins to turn on its own or becomes wildly unstable when you turn yourself.

I think the problem is two-pronged:

1. I believe the powered wheels are always slipping. I remember reading that
staticFriction is the traction of the tire when your tires are not slipping
and
kineticFriction is the traction of the tire when your tires are slipping

2. If you assume #1 is true, then the car's turning should scale as you go faster. By that, I mean the keypress for turning at high speed should not have the same direct effect to the tire as it does when you're moving slowly. This way, the car would not completely flip out to any level of keypress when you're going fast and you have a high kineticFriction.

Any ideas?

#19 No ideas at all at the moment.

I am now writing my own vechicle physics model in conjunction with AGEIAs PhysX.

#20 Try some of these settings:
-massCenter = "0 0 -0.7";
-dynamicFriction = 2.0;

And verify your pivot point for your vehicle. The default is at the bottom of the bounds and it tends to screw up the dynamics. I'm able to top speeds around 300 (units I guess would be m/s since models are in meters).
edit: kineticFriction not dynamicFriction