# [ODE] Wheel Friction

Jeff jeff at guerrillagames.net
Fri Jan 26 07:31:23 MST 2007

```David:

Thanks for your help, at this point, I'm not doing any collision except
wheel to ground collision.  Heres a video of what I'm seeing:

http://www.guerrillagames.net/sample.wmv

Maybe this will help diagnose the problem.

Here are the values I'm currently setting for a contact point:
contact[i].surface.mode = dContactSlip1 |
dContactSlip2 | dContactSoftERP | dContactSoftCFM | dContactApprox1;
contact[i].surface.mu = 1.0;
contact[i].surface.slip1 = 0.5;
contact[i].surface.slip2 = 0.5;
contact[i].surface.soft_erp = 0.5;
contact[i].surface.soft_cfm = 0.3;

I'm out of ideas.  I guess I'll start re-reading the ode pdf and see if I
can't come up with more ideas.

Thanks!
Jeff.

-----Original Message-----
From: ode-bounces at ode.org [mailto:ode-bounces at ode.org] On Behalf Of David
Walters
Sent: Thursday, January 25, 2007 3:45 AM
To: Jeff King
Cc: ode at ode.org
Subject: Re: [ODE] Wheel Friction

> I have tried messing around with the slip/mu properties with no luck.  I'm
> still a bit new, but I know I'm missing something easy.

Hi, ODE doesn't seem to natively support static friction, but you
could simulate it by setting the contact point friction for the wheel
cylinders to dInfinity until the wheel hits a small but definitely
moving velocity - at which point you lower the friction to a more
suitable value to get the desired wheel slipping, etc.

My understanding of real-world friction is a bit shaky, but I think
with this approach you're more accurately modeling the bonding that
happens when two bodies are at rest next to each other - in other
words, the tyre chemically 'sticks' to the road.

Hope this helps, or makes some small amount of sense.

Regards,
David Walters
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