In article <3f4c1278@news.povray.org>,
 "Micheal \(Mike\) Williams" <mic### [at] quixnetnet> wrote:

> Ok now I see. So it is not really tracing the ray but calculating the angles
> and intersection points?

It is tracing the ray by calculating the intersection points. (actually, 
you generally compute the intersection distance along the ray, and use 
that to compute the point)
What you are thinking of is usually called ray marching. Isosurfaces are 
solved this way, which is why they are so slow compared to other shapes.


> I gather that this method is fast but also make the math for radiosity hard.

It does not affect the math for radiosity. Radiosity does not care how 
intersections are found.


> It also explains why media effects slow rendering down tremendously.

Yes...media is done by marching the ray through the media, sampling it 
at various points along the ray. Solving it analytically would be 
faster, but far more limited.


> As for why, To make a paper cup which is rather thin but not flat I would
> have to model both the inside and out to create the thickness. That is a lot
> of surfaces. And the edges still need to be beveled some how to create the
> real highlight on the top rim. If the triangles could be rendered as though
> they have a thickness then only the shape of the cup would need to be
> rendered. The edges would naturally round over to the inside of the cup. It
> would be more like the triangle only describe the center planes of the
> object. It would be like using the triangle as a blob component where common
> edges of each triangle would not be combined.

You could simply use a macro that generates multiple triangles, 8 for 
each input triangle, arranged to make a triangular prism. This would be 
highly inefficient, better to just model the entire surface of the cup.


> Now I know some are small enough to never be seen but our brains can and do
> pick up these little missing parts. It is why indirect illumination is in
> such use now. Trying for the most real looking images.

They are also small enough that the detail will probably never show up 
in the rendering. Even a digitized photo would hide a lot of details you 
can see with the naked eye.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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