[ODE] Heightfield / ray

[David Walters]

> With the latest version AND with this version, robots with cylinders as
> wheels are making some short jumps sometimes. Sometimes too, cylinder wheel
> is falling under the eightfield ...
> My simulator let you create an eightfield using the native heigthfield
> primitive or using triangle mesh (opcode) -> those shorts jumps does not
> appears with triangles mesh, and cylinders are not falling ... (i don't know
> if it can help ...)

Hi, maybe I'm biased - but my very first port of call to debug this
would be to look at the ray/cylinder collider -- the reason I'm so
suspicious is: I wrote it :-)

I have seen, in my own tests, cylinders subtly behaving strangely over
heightfields -- I'll try to look into it myself but maybe an outside
inspection would be able to spot mistakes?

I suspect it's likely to be getting confused with collisions against
the curved surface and the caps.

Hope I've not sent you down the wrong path with my suspicions!

Regards,
David.