[ODE] surface contact points

[Tiago Rodrigues]

Hi, i'm doing some experiments with ODE.
I'm trying to do FFD (free form deformation) of the geometry of to 
colliding objects (just the drawing geometry not the fisical simulation 
one).
Right now all my objects are boxes. In a collision between 2 boxes to 
correctly perform FFD i need to know the surface collision point on each 
box.
With the information in dContact, how can find this?
I know the point is on the surface of one of the boxes, but which one? 
and to find the colliding point on the other box i can translate the 
point by the depth
times the normal or -normal? is there a way to always choose the correct 
situation (which box has the point on its surface already and what sign 
of the normal to use)?.

thanks in advance,
Tiago.