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

Raymond de Vries reedev at xs4all.nl
Sun May 13 03:31:06 MST 2007

```Hi

Look at the boxstack example for dGeomSetOffsetPosition() and
dGeomSetOffsetRotation().

regards,
Raymond

PKS123 wrote:
> Could you give me an example of a geom-offset function.
> I have ODE 0.8 and I went through its documentation, but couldn't find the
> geom-offset functions you talked about. If you can tell me one of the
> geom-offset functions, I should be able to look at the ODE source and figure
> out the rest.
>
> Thanks and Regards
> PKS123
>
>
> Jon Watte (ODE) wrote:
>
>> You can either use the geom-offset functions, which are new in ODE 0.8,
>> or you can use the GeomTransform geom, which has existed since the dawn
>> of time.
>>
>> Cheers,
>>
>>           / h+
>>
>>
>> PKS123 wrote:
>>
>>> 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
>>>>> further questions about it.
>>>>>
>>>>> 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
>>>>>
>>>>>
>>>>>
>>>> _______________________________________________
>>>> ODE mailing list
>>>> ODE at ode.org
>>>> http://mooshika.org/mailman/listinfo/ode
>>>>
>>>>
>>>>
>>>>
>>>
>>>
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>>
>>
>
>

```