[ODE] Composite Bodies

[Wesley Smith]

Hi,
I've been trying to figure out how I can make composite bodies work. 
Following Jaap's example, I've got this code:

	//assemble body[0] and body[2]
	//step1: add masses together (not reversible)
	dBodyGetMass(body[0], &m);
	dBodyGetMass(body[2], &m2);
	dMassAdd(&m, &m2);
	
	//get position of body center to be added in world coordinates
	dBodyGetRelPointPos(body[2], 0, 0, 0, result);
	
	//disconnect body from Geom
	dGeomSetBody(bodyBounds[2], 0);
	
	//bind Geom to make composite body
	dGeomSetBody(bodyBounds[2], body[0]);
	
	//set body to assembled body relative coordinates
	dBodyGetPosRelPoint(body[0], result[0], result[1], result[2], result2);
	dGeomSetPosition(bodyBounds[2], result2[0], result2[1], result2[2]);

Now, by  this point I have 2 Geoms connected to body[0] (bodyBound[0]
and bodyBound[2]).  When I query their position, I get identical
results.  As the ODE manual says,  "If the geom is attached
to a body, the body's position / rotation / quaternion will also be
changed. "  So, it seems that by adding the second Geom, I'm moving
the body position as well.  I can't seem to wrap my head around the
mechanics of composite bodies in ODE...the docs are not very specific
on this issue.  All they say are " The solution is to use a composite
collision object that is a combination of several geoms."  I'm trying
to do this, but I don't think I'm getting it right.

For instance, when I want to draw the position of the 2 parts of the
composite object, I can't get their relative positions by querying the
dBodyGetPosition because there's only 1 and dGeomGetPosition gives me
the exact same answer for both Geoms.

So, what am I missing here?

thanks,
wes