LR logreg at free.fr
Sat Mar 17 07:41:56 MST 2007

```When it does not work, the mass is a spere mass or a computed mass (but i don't
think it's really the problem, i certainly miss something ...).

you can see video at
http://files.marilou-roboticsstudio.com/ode/notorqueonsphere.avi (xvid, 3,2 mo):

you can see a ray witch apply force on contact point using dBodyAddForceAtPos:

Situation 1] Body with Sphere offsets = 0, joint hinge :
nothing appends when applying absolute force

Situation 2] Body with Box offsets = 0, joint hinge :
body turns around the joint axis (OK !!)

Situation 3] : Box and Sphere in a body, mass computed from sphere and box:
When ray is in contact whith sphere : nothing appends
When ray is in contact with box : the entire body rotates (OK !!)

Situation 4] : A body with sphere, mass= sphere:
Force is applyed to the sphere

The problem is the situation 1 : why does the sphere do not rotates ????? doeas
i have to add torque myself ?

LR

Selon "Jon Watte (ODE)" <hplus-ode at mindcontrol.org>:

> There is no difference between a box body and a sphere body except for
> the mass distribution.
> What is the mass (or, rather, inertia tensor) of the sphere when "it
> doesn't work" ?
>
> Also, adding a force that points straight towards/away from the center
> of gravity will add no torque.
>
> Cheers,
>
>           / h+
>
>
> LR wrote:
> > Hi,
> >
> >
> > using dBodyAddForceAtPos on a box (box is centered to its body, body is
> centered
> > on its joint axis), makes the box rotates around its joint axis. It seems
> the
> > absolute force is decomposed to produce force AND torque ... (OK)
> >
> > Doing the same thing on a sphere does not produce any torque ...
> >
> > Is it notmal or i'm missing something ?
> >
> > Thank you for your help.
> >
> > LR
> >
> > (if my explains are not enaught, i can produce video )
> >
> >
> > --
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> > ODE mailing list
> > ODE at ode.org
> > http://mooshika.org/mailman/listinfo/ode
> >
> >
> >
>

--
```