"Mark Weyer" <nomail@nomail> wrote:
> > You are right, when I look at it, it is essentially equal to a perspective
> > camera (except inside out, which isn't possible with a regular camera except by
> > using refractive lenses).  But this is exactly how I understood it from
> > wikipedia, each ray passes from the opposite pole, straight through the sphere
> > surface, onto the projection plane.  To me it appears that is supposed to be
> > exactly equale to a perspective projection (with a 90deg viewing angle), but
> > that it is traditionally meant as a means of projecting a spherical surface
> > onto a flat surface.  We are thinking of it as 3d objects rather than 2
> > surfaces which I think confuses the matter in our interpretation.
>
> Right. If the scene is entirely contained in the (surface of) the sphere,
> then a perspective camera suffices. The original poster wanted something
> different, though: To apply this kind of projection after the scene has
> been projected to the sphere. So, the camera must provide two projections
> at once, giving importance to the angle at which a ray of vision hits the
> sphere.
>
>   Mark Weyer

There's a MUCH easier way to create a stereographic projection in POV-Ray.  No
math, no fancy code.  I can provide a diagram for anyone who is interested.  If
interested, respond to my e-mail address.  i won't necessarily monitor the
group.

Rick Smith

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