In article <41474dbe@news.povray.org>, Warp <war### [at] tagpovrayorg> 
wrote:

>   Raytracing a torus is done by calculating the intersections of a
> line and fourth order polynomial. I suppose solving the intersection
> can be optimized a bit when the torus is sitting in the origin

This is actually the case for cylinders and cones...POV transforms the 
cylinders internally to the proper position. However, it is so 
inconvenient to rotate and translate axis-aligned cylinders into the 
proper position that this is necessary just to make using them 
practical. For a torus, it's pretty easy to translate it into place. A 
normal vector would have been very useful in earlier versions, but we 
have macros for pointing it along a specified direction now.

-- 
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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