Warp <war### [at] tagpovrayorg> wrote in message news:39d35005@news.povray.org...

>   Secondly, rotating an evenly random angle around the y-axis and then
> an evenly random angle around the z-axis has an undesired effect: You
> will have more stars near the y-axis (ie. around <0,1000,0>) than near
> the x-z plane.
>   That is, the stars are not evenly scattered around the sky but there are
> more stars directly "up" than near the "horizon".

I noticed that but thought it was just a coincidence

>   If you want an even distribution of stars you have to use a bit more
> complicated algorithm. For example:
>   1) Calculate a random point inside a sphere (eg. a unit sphere). The
> random distribution must be even.
>   2) Translate this point in the direction origin-point (ie. multiply it
by
> a value) so that its distance from the origin will be the desired (eg.
1000).
>
>   For example something like this:

<snip code>

Thanks, I'll take a look at that

Gail

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