In article <3C7789EC.8C504189@gmx.de>, Tim Nikias <tim### [at] gmxde> 
wrote:

> The problem is, I don't need the tangent (I was able
> to figure that out, still, thanks for the reply). I need
> to find the centrifugal-force, and I don't know if
> tangents actually help me there...

Find the tangent at the point, and the tangent a little distance ahead. 
The amount of force will be related to the angle between these tangents 
(normalize them, and the dot product will be the cosine of the angle) 
and the distance between the two points on the spline.
Find the angle first, if it is too small just don't bother with the 
force calculations.
A vector perpendicular to the direction of the force can be found by 
taking the cross product of the two tangents. You can then find the 
direction of force by getting the cross product of this vector with the 
first tangent.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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