"Mark M. Wilson" wrote:
> 
> Could someone explain them to a new user, not just to POV-Ray, but
> raytracing and any type of computer graphics at all? In more-or-less
> plain English?

Isosurfaces are equipotential surfaces of 3D mathematical functions,
usually written in the form:

f(x, y, z)

This means that all points in space (x, y, z) where the function has a
certain value (0 by default in Povray) form a surface.  

This is of course quite mathematical, but that's life... For details see a
good math book. :-)

The raytracer now has to find the intersection of a line (ray) with the
object - not a trivial task since you only have the (possibly complicated)
function.  Povray directly traces the isosurfaces which involves a lot of
evaluations of the function and is quite critical when the function value
changes very fast (high gradient).  Another method would be tesselating
the isosurface first and rendering the resulting mesh.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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