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

PKS123 prashant.coder at gmail.com
Sun May 13 02:18:07 MST 2007

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

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/
>>> The bold links are downloadable.
>>> 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
>>>> ask
>>>> again.
>>>> My question is how do I lower the center of mass of a ODE Body. The
>>>> answer
>>>> 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
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>>> ODE at ode.org
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