[ODE] odd contact behavior -- no bounce for heavy objects?

[jon klein]

I'm experiencing some odd behavior with large bouncing objects.
If I let a sphere of radius .5/density 1.0 to drop from a height of
20 with a coefficient of restitution of 1.0, I get a totally elastic
collision and the sphere goes back to (or relatively close to, at
least) 20.

The problem is that if I set the density to 100 (or if I make a
change in radius resulting in a similar mass) there is almost
no bounce at all.  This can be seen in test_boxstack by setting
the contact bounce parameter to 1.0, bounce_vel to 0.0, and then
creating spheres of radius 1 with density 100.

I realize that the masses of such objects are going to be quite
high, but my understanding of how the coefficient of restitution
should work is that mass should not matter -- the kinetic energy
should be preserved and the sphere should bounce up with
approximately the same velocity it came down with.

Can anybody shed any light on this?  Is this a bug, or is there
something wrong with my understanding of how the collision
should behave?

Thanks

- jon klein