In article <4045b5ce@news.povray.org> , "Tim Nikias v2.0" <tim.nikias (@) 
nolights.de> wrote:

> Sorry for being dense, but let me just think: I shoot a ray and hit an
> object. When it gets reflected or refracted, I go to the next trace_level
> until max_trace_level is reached. I still don't get what max_intersections
> actually saves and why. If I'm annoying, then just settle it with "too
> technical", okay? :-)
>
> I guess I'd understand it, but I don't want to waste your time, so feel free
> to tell me to bugger off. ;-)

You need to understand the difference between a ray and a ray ;-)  There are
two kinds of rays: Lets call them mathematical rays and physical rays.

Mathematically a ray is just a line that extended to infinity in one
direction and has exactly one end if you follow the other direction (well,
you remember this from school, I guess).

In physics however, the concept of a ray is less well defined.  Of course,
first you have to remember that there are neither light rays nor viewing
rays.  What is frequently called a ray is usually light in its particle
form, and those particle streams can get partially redirected.

So, while for you as a user POV-Ray shoots rays and follows them through the
scene, and occasionally when they hit an object might split them, in order
to do all this, POV-Ray has to use the mathematical definition of what a ray
is.  Along this ray, POV-Ray can find any number of objects.  In order to
determine which object is closest, it needs to find all objects that are in
the way of this ray (well, not really all in every case, but that is another
story).  For every object the intersection (and some more information) needs
to be stored.  For simplicity (and memory usage reduction needed in the old
days) there is an upper limit of the number of intersections POV-Ray will
store per ray, and this is the number is what you can alter by changing
max_intersections.

    Thorsten

PS: Sorry of all the parenthesis, but I don't want to get a comment about
being inaccurate by any of the usual suspects ;-)

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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