In article <38727F66.741BE70D@pacbell.net>, lin### [at] povrayorg 
wrote:

> I realize that many functions/objects in pov default to a unit square but
> what I do not understand is why manual bounding affects this and why it
> is not documented as doing so. I also need to know how one determines the
> size of the bounding volume to use for a given iso surface object or if
> it can be any arbitrary amount.

"bounded_by" does not work the same in isosurfaces as it does for other 
shapes, it just uses a unit box as default. The bounding shape is just 
the "container" for the isosurface. I really think this part of the 
syntax should be changed when the isosurface is added to the official 
version, and be replaced with something like "contained_by".
The size of the bounding shape doesn't really matter, if it is smaller 
than the resulting shape it will be the same as intersecting the 
isosurface with the bounding shape.
The only ways to determine the correct size are trial and error or 
figuring out the furthest reach of the object from the equation and the 
threshold value. I usually guess at it from the equation and then use 
trial and error to get a shape that fits correctly. I also sometimes 
switch to clipped_by(which does the same thing but leaves the surfaces 
open) to make sure there are no intersecting points.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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