[ODE] 3 beginner questions

[Bob Ives]

Thanks for the replies, people.  Its good to find such a helpful usergroup.

to David McClurg:
2. I am applying both a force for velocity damping and a torque for rolling resistance, though right now I´m more interested in the
former.  I´ve tried just the velocity damping, a combination of both, total damping ( coefficients of -1.0 for both ), your constant
force method, but nothing helps me to bring my objects to a quick stop except paradoxically reducing their mass.   Thanks for your
pragmatic method, with tweaking it worked for me but I´m hesitating to use it for the sensitivity of the friction parameter to body
velocity...  Instead I´m just leaving it as force applied based on a high (-0.9)  coefficient of the linear velocity.

to david@csworkbench.com:
2. Drag.  I have now experimented with various flags in the contact mode parameter.  From the beginning I had the dContactApprox1
flag included, so thats not the problem, unless another flag is interfering.  But trying to remove other so far flags retains this
behaviour, ie that the time taken to slide to a stop increases with extra density...  Anyway any illumination you give on how
combining these flags and their parameters can effect contact response is very welcome.
One thing you mentioned in your later elaboration of drag and friction is that you´d apply the former after collision detection but
before the step.  I´m doing this after the step, but I´m not sure if that might be significant.  It seems that the constraints
entailed by the contact join generate the forces/torques during the step....  si it doesn´t matter if I try to intervene before or
after. The problem is probably as you suggested originally that I´m generating the wring sort of contact joints.

Btw regarding aerodynamic drag, I´d love to see that implimented.   The moment that really convinced me how important good dynamics
could be was watching Karl Sims swimming creatures evolve to use their limbs as paddles :)=

3. I´ve added bounding planes as per your suggestion.  Duh!  One curious thing though: I use the standard ax+bx+cx+d=0 equation for
my planes, but I found I had to negate d when passing the plane to ode for the collision to work correctly ( at least with
dCollideSpherePlane ).  Does Ode use ax+bx+cx-d=0 or is that a bug?