The way NASA animates galaxies is to animate each star independantly.
Perhaps you could do something similar by using 10 or 20 concentric rings
instead of millions of points.

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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