[ODE] Some objects pass through other objects

[Bram Stolk]

Keith Wiley wrote:

> 
> However, when I drop a canonball into the cup of the pendulum, it  falls 
> right through the pendulum to the ground as if there is no  collision 
> detection going on.  Even weirder, the ball does  successfully collide 
> (and rest against) the pendulum sometimes, but  not always.  In 
> particular, it falls through the pendulum under two  specified 
> circumstances.  One, when the cup of the trebuchet is  resting on the 
> ground (so the canonball drops into a cup that is  already at ground 
> level, ready for launch).  It passes right through  and rolls away on 
> the ground.  Two, if I "trick" it into accepting  the canonball by not 
> adding the canonball until a moment *after* I  release the trebuchet (so 
> the cup is already moving upwards and no  longer on the ground when the 
> canonball is added), then the canonball  gets pushed by the pendulum and 
> cup for some of the rotation, but  before the rotation completes, it 
> falls through the pendulum (you can  also get the pendulum to "accept" 

Wow!
Cool demo!

It works for me (UNSTABLE branch from cvs)
My observations:

1) both cases "cup on grnd", "trick", show proper collisions for sphere.

2) the cup is very jiggly.

3) in one run, I managed to hit the buggy on its roof *grin*
    the buggy then proceeded a bit to the wall. Looked great.

My remarks:

- Try the cvs unstable version to see if it works for you as well

- I don't think your "trick shot" is valid: If you introduce new
   objs, or change positions, you must present them to the sim
   in a non colliding state. At least, this is what I recall
   reading in the ode manual.

- This demo could be included in test/ in CVS unstable.

    Bram