> It actually simulates the light travelling through the scene. And modern
> hardware can render a sphere + light source at a decent framerate.

Yeah, I know how a raytracer works - I've built one ;-)

I'd be interested to see one go in realtime... (Actually, some of my Chaos
Pendulunm renders nearly had POV-Ray in realtime... I presume it's preview
window isn't designed with realtime performance in mind. It goes way faster
if I switch it off!)

> They can. Texturing calculations also account for a lot, especially with
> the more complex procedural textures, but the main reason raytracing is
> slower is that it traces the rays of light through the scene instead of
> projecting triangles onto an image plane and "painting" them onto the
> image with an image map stretched across them.

I've yet to see texturing have any significant effect on my renders...
Complex object geometry slows it to a crawl, as does excessive lighting, and
media (which is a whole OTHER kettle of fish - you could do media
simulations without a raytracer). But texturing has never seemed to have any
effect at all. (Until you turn on AA, or reflection/refraction, but these
are due to other effects.)

> Correct.

Yay!

> POV builds such a structure automatically,
> though manual bounding can still give better results in some cases.

...such as building polyhedrons out of planes using CSG? (I do this all the
time... *is* there any other way to build polyhedrons in POV?!?)

> > Is that or is that not what POV-Ray's vista buffer and light buffers are
> > designed to do? And would I be right in thinking that these don't apply
to
> > reflection and refraction?
>
> Correct. These techniques are useful when you have a lot of rays from a
> known location. Reflections and refractions spawn rays from anywhere in
> the scene, so they can't be optimized in this way. The bounding tree
> works no matter where the ray comes from, though.

The other night I convinced myself that voxels were the answer to all our
problems, and I was about to post a message damanding that it be implemented
immediately in the name of speed. Fortunately, I just happened to enguage my
brain first. And I realised that it's actually a pretty lame idea after all.
Glad I didn't post that suggestion!

Andrew.

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