"Tim Nikias" wrote:
> Christopher Hames Huff has replied and given me
> some mathematical insight with cross-products
> and dot-products. I'll guess going from there, I'll
> find a solution to what I am heading for.

I didn't know that was your problem. :)

It's worth noting that the solution I suggested still is valid. Chris Huff
suggested a method involving angles and checking the spline at four
different places (in order to get two tangents), while my method doesn't
involve angles (or dot products) and needs only the spline tested at three
places.

But you basically get the same thing. It sounds like your problem was that
you wanted the centrifugal force vector calculated to be perpendicular to
the tangent of the spline at that point. Using my own example as basis this
is very easy as you already have the tangent, which is (B-A). Now you just
need to adjust the vector (P-C) so that it's perpendicular to the vector
(B-A). POV-Ray 3.5 has a macro to do that, called VPerp_Adjust. The
VPerp_Adjust macro do automatically the things with vcross that Chris Huff
talked about. You can read about the macro in the documentation.

Rune
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