[ODE] ODE Message 2: Vector has zero size and NaN values.

[Remi Ricard]

Hi,

> 
> I'm currently working in an interactive application with physics and
> I've been getting this strange warning message:
> 
> ODE Message 2: Vector has zero size
> 
> coming from dNormalize4() and shortly after this, ODE starts spitting
> out invalid floating point values (NaNs) for body positions inside the
> simulation.
> 
> Any clue has to what can usually cause this error? I've checked
> collision functions but everything's quite simple and no strange
> values pop up.
> 
> I'm hammering in positions for dynamic collision bodies every few
> frames so I thought this might influence the contacts, but I really
> have no clue has to what I should be looking for.


I was getting this problem when 2 collisions were occuring for the same 
bodies at the "same" position.

Ex:
Geom_1_0 of Body_1 collides with Geom2 of Body_2 at pos= 1,2,3
Geom_1_1 of Body_1 collides with Geom2 of Body_2 at pos=1,2,3.

This is possible if Geom_1_0 and Geom_1_1 share a common vertex and this 
vertex collides with Geom2


Remi