For the knot problem, have you looked at Knot 3.7? It is a 3D knot design
software that also animates. I have it on the Mac, don't know if it's on
other platforms. It's a fascinating and very well done application. I can
send you some samples if you'd like.

[Image]
steve

Gilles ADAM wrote:

> Hello...
>
> 1 - I use PoV 3.1 to model various astronomical phenomena (animations
> to be soon on the WEB...), and general physics phenomena for education.
> I recently modelled (artist's view only, as only a rough sketch
> of the physical processes is available !)
> the central parts of an active nucleus galaxy (the thing with a black
> hole in the center), made it rotate, and so on. Nice, but it rotates as
> a solid
> object, which is wrong. Does anybody know of a way of "warping"
> continuously the "spiral" texture to make it rotate faster in the
> central
> parts than in the outer parts ? I searched a lot in the (excellent)
> in-line doc, with no success...  Maybe I missed something...
>
> 2 - I am going to try to write an external program computing a B-spline
> approximation to a set of points ( two sets in fact, one for the camera,
>
> the other for the "flying object" ) The best way I know so far is using
> PCG2.21 (Patrick's Curve Generator), which takes as input the clock
> variable
> and a spline.dat ASCII file containing the knots of the path, and
> outputs
> an ASCII file wtih a set of #declare. The whole thing is invoqued via a
> Pre_Frame_Command in the .ini file. This is the structure which is
> planned for the code I am about to write. But the PGC program does not
> compute the local curvature and twist of the 3D spline, which are needed
> to
> compute the "correct" attitude of the plane, and cannot compute two
> distinct
> spline approximations on two data sets for the same clock value.
> The "spline" add-on from Chris Colefax is not well suited for multiple
> knot
> splines, as you must give all the control points to be used for all the
> knots;
> or did I miss something ?
> I tried AnimSys, too, but the "plane" attitude is not computed from the
> fly path shape, just given a priori.
> Before engaging further into  development, I would like to know
> if anybody heard about something addressing this problem...
> It should have been solved by all the people working in the flight
> simulation
> area...
>
> 3 - I used (before switching to the last release of PoV for Windows) the
>
> dispersion patch. I was able to render all kinds of gems, to demonstrate
>
> refraction into complex objects during physics courses. Great, but I was
>
> not able to obtain a spectrum-like patch of light on a screen following
> a glass ball, although I got nice effects in the ball itself.
> Is that normal, or just a matter of wrong code ?
> I tried to disperse light through a prism, and get a spectrum on a
> screen :
> no result...
>
> Many thanks to the fabulous POV team !
>
> Gilles AdamObservatoire de Lyon
> 69561 Saint Genis Laval cedex
> France
> ga### [at] obsuniv-lyon1fr

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