# [ODE] Modeling a snowmobile

Megan Fox shalinor at gmail.com
Fri Jul 28 09:58:39 MST 2006

```... to add to this - if you're an idiot (like me) and neglect to think
about using the contact joint at the end of the ray cast, you can
still do the same simulation, but it will be MAGNITUDES more complex
and lengthy to get it all working right.  It will take huge amounts of
balancing, and the code you're using to fake friction or whatever else
will outright break unexpectedly every time you add something new to
the scene.

So, yeah, definately use the joint, don't make the mistake of thinking
avoiding it might be easier or that you'll want the added control (you
won't).

On 7/28/06, Jon Watte (ODE) <hplus-ode at mindcontrol.org> wrote:
>
> When modeling vehicles, do not underestimate the power of the contact
> joint. The contact joint has the following things you might be
> interested in:
>
> 0) You should always use dContactApprox1. There is no reason not to use
> it; the difference in math cost is negligible these days.
> 1) You can set a "forward direction", and together with the contact
> normal direction, that'll give you a "side direction".
> 2) You can set slippage and friction in each of the "forward" and
> "sideways" directions. This allows you to implement steering and sliding.
> 3) You can set how hard or soft the contact is. This allows you to
> implement suspension.
> 4) The contact joint allows you to set an "assumed velocity" at the
> point of contact. This allows you to implement traction/power.
>
> Now, there is nothing that says you have to create a contact joint based
> on the results of a primitive collision. You could just as easily create
> it based on a raycast. In many cases, it's actually easier to do that --
> see the "raycar" example for how to do this with a car.
>
> You can then approximate the non-traction parts of the vehicle with
> simple dumb geometry, such as a box or whatever.
>
> Cheers,
>
>              / h+
>
>
> Jules Robichaud Gagnon wrote:
> > Hi everybody,
> >
> > I am working with a team of people to build a snowmobile game but we have
> > some trouble figuring how to create a realistic and optimised physical model
> > for the snowmobile.
> >
> > We thought of some possibilities:
> >
> > Using a capsule for each of the skis in the front to have the parts slide on
> > the snow or putting two wheels for each skis and have them roll like some
> > sort of skate boards. For the chain of the snowmobile we also thought of
> > using three wheels or a long capsule to have it slide. We are not sure what
> > is better between sliding, rolling or a mix of both.
> >
> > Anyone of you has any ideas or recommendations how to build this snowmobile
> > the most realistic possible?
> >
>
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--
-Megan Fox
Idyllon, LLC
http://shalinor.circustent.us/megan/resume/
```