reference plane rotates, why?

the planes that i am using for a rotate component switches direction unexpectedly.
how can i fix this?

thanks
matei

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Permalink Reply by Côme Ménage on September 30, 2010 at 2:13am

Hi,

the planes along the curves shifted axis all of a sudden. A perpendicular surface frame that is used as base for the circles seems to fix it. Not sure to be clear. I attached the definition.

Côme

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birdcagerotationok.ghx, 207 KB

Permalink Reply by matei denes on September 30, 2010 at 7:32am

thank you
works perfectly now

Permalink Reply by WT4 on September 30, 2010 at 7:42am

You are encountering a phenomenon sometimes referred to as a gimball lock. It occurs when the angle of 90 degrees is approached. You will appreciate that the tan(89.999) is +infinity but then tan(90.001) is -infinity. This is the reason why the plane seems to flip over. The solution would be to ensure that in defining your planes, you keep the orientation within the -89.999 to +89.999 domain.

Permalink Reply by matei denes on September 30, 2010 at 8:42am

i figured it was something about the approach to 90 degrees, but didn't know what to do about it
seems like the perpendicular surface frame avoids that issue somehow.
i usually like to know why things work or don't but this one is beyond me as to why one component does and the other does not.

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