Simen Kvaal wrote:

> So: I wonder if there exists some extensive documentation on Isosurfaces?
> Are there bug fixes? Should we send reports to NathanKopp? Someone else?
>

My 2 cents, from an "old", empirical user of isosurfaces, since they were
implemented in Ryoichi Suzuki's patch in 1996
- They were never fully documented, though the current doc is the best there
ever was. I remember testing the functions one by one trying to guess what each
parameter did !
I think that it's said in the current Megapov doc that what we know about the
iso were either derived from the original Suzuki docs, or guessed from people
clever enough to understand the code and the theory behind it.
- The syntax and the code was never streamlined, and never seemed very
consistent. For instance, some of the functions accepted in the function{}
statement are specific to it, like "^" instead of pow(), while other are not
supported. The use of commas, <,> and quotes never seemed very logical to me,
and neither was the use of "bounded_by" (now replaced by "contained_by"). This
is partly explained by the fact that this patch implemented functions that
didn't exist in POV back then (it started as a POV 2 patch).
- There was always strange things happening with them, like crashes and black
dots, or parts of the picture disappearing, or the render getting impossibly
slow, or shapes actually changing between version updates. Again, this works
much better now.
- My guess is that there is a lot of work to be done by the POV team before the
isosurfaces can be as reliable as the rest of the pov objects. Unless I'm
mistaken, they have been working on it (at least Chris Young talked about it in
his message "POV-Ray plans for v3.1 and beyond" of 2/2/99).
- However I'm in no position to complain about the isosurfaces because in spite
of their problems they've been absolutely fundamental in my POV work !

G.

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