On Sun, 18 Jun 2000 21:04:42 +0000, Francois Dispot
<woz### [at] club-internetfr> wrote:

>A sample from the current work, which is a megapov macro to make tyres
>(1st pic) with isosurfaces given the shape of the "sculptures" (en ?) as
>a png bitmap (2nd pic).

Ah, so you've actually made it! Look great and quite like a real
thing. 

>Now I have a problem. The lateral parts of the tyres are made with
>lathes, and I would like to connect them smoothly to the deepest part of
>my isosurface, which is a 4th degree profile. I know the tangent to my
>profile, and need to keep the same on the lathe. So my question is: what
>is the slope of a cubic_spline lathe profile at one of its control
>points?

Just out of curiosity, isn't the formula in the source code of POV? If
you can't find it, can you use trace() ? Lastly, why don't you use a
bezier spline lathe? At least you won't be wondering where its
tangents are pointing.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG      e-mail : pet### [at] tagpovrayorg

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