Thanks Kim. I'll pass a little more info on what I'm trying to
achieve. It's a shader (surprize surprize) and I want to be able to
generate X normals given X and a seed. So I can reproduce the same
normals again and again.... While it doesn't matter if the
distribution of these points is even or not (actually it kindof kills
the point of randomly generating them from a seed if it is) I don't
want it to bias towards the poles because this will look ugly.
Cheers,
Alan.
On 6/14/05, kim aldis <kim(at)aldis.org.uk> wrote:
> But of course, this won't give you absolute control over exactly how many
> points. You'd be stuck whatever the subd gave you.
>
> Relaxation?
>
>
> > -----Original Message-----
> > From: owner-xsi(at)Softimage.COM
> > [mailto:owner-xsi(at)Softimage.COM] On Behalf Of kim aldis
> > Sent: 14 June 2005 16:08
> > To: XSI(at)Softimage.COM
> > Subject: RE: Random points on a unit sphere without biasing
> >
> > Geodesic dome. Infact there's no such thing as a perfectly
> > even distribution of points over a sphere greater than the
> > number of points on an icosahedron (20 faces) but Buckminster
> > Fuller got pretty close with his domes by splitting the
> > icosahedron across it's faces. He did it by putting points in
> > the middle of each face then triangulating the new points,
> > omitting the old. You can get a good way into complexities by
> > doing this recursively.
> >
> > If you can't use the xsi primitive as a starting point then
> > you can generate the starting icosahedron but I remember it
> > proved fiddly when I last tried it.
> >
> > None of the XSI subdees give the results you need.
> >
> >
> >
> > > -----Original Message-----
> > > From: owner-xsi(at)Softimage.COM
> > > [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Alan Jones
> > > Sent: 14 June 2005 15:55
> > > To: xsi(at)Softimage.COM
> > > Subject: Random points on a unit sphere without biasing
> > >
> > > Hi All,
> > >
> > > This is to the maths geniuses in the room. I want to
> > generate X number
> > > of points on a unit sphere, but be sure I won't have any biasing
> > > involved.
> > >
> > > My first thought was just to use a couple of random numbers (let's
> > > assume they don't have any bias) and then use those with a
> > few sin and
> > > cos function etc to generate the points.
> > > Though I have a feeling that would give me more points around the
> > > poles.
> > >
> > > Anyone have some good suggestions?
> > >
> > > Cheers,
> > >
> > > Alan.
> > >
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