Wasn't it Retsam who wrote:
>Tyler Eaves wrote:
>>
>>Should produce a perfect 180 curve, with straght lines entering and exiting.
>>The final goal of the project is to render a rollercoaster design, so smooth
>>curves are a must!
>>
>
>Actually, that wouldn't be the "smoothest" curve.  Going from straight to a
>sharp curve without any transition is not smooth.  Going from a curve to
>straight without a transition is not smooth.  People in a roller coaster
>would definitely feel like they were being jerked around at the
>transitions.  Literally.  You would have an infinite 3rd derivative at the
>transitions.  And in technical circles, the the third derivative is called
>"jerk".
>
>0th derivative: position
>1st derivative: velocity
>2nd derivative: acceleration
>3rd derivative: jerk

Actually, for rollercoasters, the 4th derivative has a significant
effect on the tendency of the passengers to vomit. It's called "jounce".

I believe that Retsam's problem is that if he doesn't specify the spline
type, then it defaults to "linear_spline". He needs to specify one of
the other spline types.

-- 
Mike Williams
Gentleman of Leisure

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