[ODE] Composite Body - Center of Mass

[achaudhry]

Hi all, 

While working on composite bodies, i was earlier suggested I use
dGeomSetOffsetPosition for adding geoms to a single body(tower). I tried
creating a simple tower structure with 4 legs and cnnecting rods. 

the structure looked fine (in the visual world) , but while just checking the
position of the tower, i used dBodyGetPosition(tower) and displayed t at every
simulation step. I observed that while the structure was stable but the
(x,y,z) coordinates of the tower body was changing continuously. And also the
values were extremely large. 


My ques:-

1. why are the values so large of dBodyGetPosition(tower) , which is a
composite body. 

2. I tried connecting wheels to this body and the joint wont cnnect saying
joint and bodies must be of the same world. I checked a lot, but couldnt find
the problem, both the joint and the bodies were created in the same world. 
any suggestions on this one?

3. Can the body and the wheels of a buggy be made a composite body, if yes
then will the wheels stil be able to rotate .

thanking in advance
amber