btAtan2Fast too approximate

[marcimatz]

Hello,

In the last few days I have been wondering why my PID position controller doesn't work as nicely as it should with hinges. I finally tracked down my problem to the "btAtan2Fast" function used in the "btHingeConstraint::getHingeAngle".
When I replaced the "btAtan2Fast" call with a simple "atan2" call, my position controller worked like a charm.
I didn't measure it, but it seems that the "btAtan2Fast" function has a precision of +-4 degrees in some situations. My question is: is the speed increase of "btAtan2Fast" really worth the reduction in precision?

Thanks for any insight!

[rponomarev]

Yes, btAtan2Fast() is not precise.
I replaced it by btAtan2() as of r1833
Hopefully it will not hurt performance (unless you have several thousand of hinges in your scene)

Thanks for pointing on that,
Roman

[Flix]

rponomarev wrote:

I replaced it by btAtan2() as of r1833

AFAIK there are still some btAtan2Fast calls in btConeTwistContraint.cpp.

(Or maybe you can temporary replace it in btScalar.h and make it call btAtan2 to avoid these problems, in case somebody will find a better implementation in the future).

Regards,
Flix