[ODE] Another strange wheel rotation

[Remko Jacobs (act-3d.com)]

Ok, it was a stupid mistake. The hinges where initialized AFTER the first   
simulation step. The wheels moved down because of the gravity and the   
rotation point was shifted. Changing the order fixed this.

 -Remko

 -----Original Message-----
From: Remko Jacobs (act-3d.com)
Sent: Thursday, October 17, 2002 11:40 AM
To: ode@q12.org; Remko Jacobs (act-3d.com)
Subject: [ODE] Another strange wheel rotation bug

   

I fixed the 'bending wheels' problem using the following methods. The
problem still exists but at least you can reduce it to acceptable levels:

 - Decrease the step size (update of 200-300Hz)
 - Different CFM and ERP values
 - Different masses
 - Bigger wheels (The bigger the wheels, the slower they have to turn for   
    

the same speed)

I'm experimenting with a driving simulation and the results are stunning!   
    

However, after some experimentation, the car started to bounce and the
handling was completely gone.

It turned out that the wheel is not rotating around it's axis but around   
    

a point slightly above that. Gravity was causing this offset. Gravity
pulls the wheel down so the rotation axis of the hinge is too high. What   
    

really surprised me, is the solution I found:

When I set the gravity to zero the problem does not occur (as expected).   
    

When I crank up the gravity while the simulation is running, the bug does   
    

not come back but the wheel rotates around the correct point. Does anyone   
    

has an explanation for this? Why the rotation screws up when I initialize   
    

with gravity?

 -Remko




_______________________________________________
ODE mailing list
ODE@q12.org
http://q12.org/mailman/listinfo/ode