The video showing this behaviour http://www.youtube.com/watch?v=VFR4mwmWa-M
From IRC:
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(8:36:33 PM) Kulik: Hi, I just found out that 6DOF motors and springs are very sensitive to changes in timestep. the smaller the timestep, the stronger the motors get. Is that expected or is there perhaps something wrong with my integration? Thanks for any pointers :-)
(8:38:19 PM) Kulik: I will do a small comparison video to demonstrate this, give me a few minutes :)
(9:08:36 PM) Kulik: Ok, this is how it looks: http://www.youtube.com/watch?v=VFR4mwmWa-M
(9:08:51 PM) Kulik: if the source is relevant, I can commit and post the repository URL
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btRotationalMotor* motor = rearLeftWheel->getRotationalMotor(0); // I have "reordered" the 6DOF to allow suspension, steering and wheel rotation using just one constraint
motor->targetVelocity = -300;
motor->maxForce = mTransmission->getOutputPower(); // this changes as the throttle changes
I have also observed another really weird behavior. When the car is on the "roof" and the throttle is pinned the wheels spin up to targetVelocity and then suddenly stop and spin up again. I think my naive idea of how motors work is wrong