Hi Fredrik,

Funny you should ask, we were just discussing that here http://moi3d.com/forum/index.php?webtag=MOI&msg=2062.35
I think it answers your question.

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Oh

Thanks Danny.
It almost answers my question. But i still don't understand what decides the amount of rotation along the curves tangent.

Great work on the camera btw, looks amazing.

-F

It's that named "banking" : a sort of centrifugal force :)
But waiting the Michael explanation ;)

Hi Fredrik, that twisting is provided by a mechanism called "Parallel transport":
http://en.wikipedia.org/wiki/Parallel_transport

It is also sometimes called a "Bishop" frame:
Bishop, R. L. "There is more than one way to frame a curve.", American Mathematical Monthly (1975) pp. 245-251

It is a bit difficult to describe shortly, but it basically has a kind of continuously minimally changing twist instead of there being any sudden changes.

Sometimes it is also called a "relatively parallel" frame if I remember right.

The whole problem of how to assign a perpendicular direction to a curve tangent in a coherent way as it travels along the curve is often referred to as "curve framing".

- Michael

Thanks Michael

Interesting stuff, although it seems a bit complicated.

:)