# [ODE] How to shift the center of mass of a Geom using Transform Object - Some questions

PKS123 prashant.coder at gmail.com
Sat May 12 03:42:58 MST 2007

```But, doesn't the ODE Engine itself place the Geom at the body's position and
visa-vis on its own.
That is, if i place a body at (x,y,z) using dBodySetPosition() function,
doesn't the geom get placed at (x,y,z) autometically. Thats what the
documentation says. So, how can i offset the Geom position with respect to
the body??

Thanks and Regards
PKS123

Jon Watte (ODE) wrote:
>
> Actually, as of ODE 0.8, there is a simpler way: you can set the offset
> of each geom instead. So to lower the center of mass, just raise each of
> the geoms. The center of the body and the center of the mass is always
> the same thing in ODE -- the "offset" part of the mass is ignored.
>
> If you want a sample for how to use geom transforms (the old way), check
> out the RayCar sample: http://www.mindcontrol.org/~hplus/raycar/
>
> Cheers,
>
>              / h+
>
>
> PKS123 wrote:
>> I know that this is a hackneyed question and there are posts which give
>> the
>> answers, but none of them give the answer to my satisfaction. So, i'll
>> again.
>>
>> My question is how do I lower the center of mass of a ODE Body. The
>> that I know of is, "by using the ODE transform object". But I have some
>>
>> 1. The Transform object claims to change the point of reference of a
>> body.
>> Do point of reference and center of mass mean the same thing in ODE?
>>
>> 2. Is there any example anywhere of how to use the Transform Object. Its
>> not
>> there in any of the ODE demos.
>>
>> 3. Will the transform object inherit all the geometrical properties
>> (sides
>> in case of a box) and behave exactly the same was as a (box) geom would
>> have, or is there an unsaid difference of behavior somewhere.
>>
>> Thanks and Regards
>> PKS123
>>
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>
>

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