# [ODE] mass of collisions - imagine a brush

Patrick Enoch Hendrix_ at gmx.net
Wed May 9 03:47:37 MST 2007

```Hi,

A) if you get a good solution, I would be interested, too.

B) this is how i would do it:
- have all bristles as single geoms, even worse, subdivide the bristles into several parts connected by universal joints.
- the bristles are connected to the head by a ball joint; preferably a joint that does allow rotation "to the sides", but not "twisting rotation". I have posted the "free6" joint to the list (that is capable of this), but the email has not been approved by a moderator.
- the bristles can collide among themselves, ...
- but not a single bristle with itself (lets hope they dont bend too far so self-intersection is possible)
- the joints stiffness should be possible via a motor with rotational velocity of zero and a maxforce (however, this wont make the bristle return to its original "straight" state)
- you need to determine the relative rotation of the subdivided parts of the bristle (a relative quat), and add a restoring torque. maybe this should be built into the joint itself.

best,
Patrick

-------- Original-Nachricht --------
Datum: Wed, 9 May 2007 00:00:29 +0200
Von: Tobias Zimmer <tozim at gmx.de>
An: ode at ode.org
Betreff: [ODE] mass of collisions - imagine a brush

> Hi!
>
> I am new to this list and started working with ODE some time ago.
> Luckily the mailing list works now and
> at last I could subscribe.
>
> Well, to the problem:
>
> I want to simulate something like a brush. That leads to two problems:
>
> - flexibility of the bristles
> - collision of the bristles
>
>
> I thought about solving the first problem with universal joints along
> the bristle, which is build by cylinders with very
> small radius. With LoStopParam=0 and a very small HiStop that should
> somehow work like flexible then.
>
> To the second question, the collision. The bristles of the brush are
> all connected to the head. So first I've put all
> in one geom, because they collide with the ground all together. But
> what about the collisions between the bristles?
> Do I have to use one seperate geom for any bristle or is it possible
> to combine all of them in one geom and then
> build a second geom for each of them?
>
>
> Has anybody worked with something like that yet or perhaps some ideas?
>
> Help would be really appreciated!
>
> Regards,
> T.
>
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> ODE at ode.org
> http://ode.org/mailman/listinfo/ode

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