Well, it depends what you're doing.

The main advantage I find in using NURBSs is adaptive generation and
degradation of the final rendered mesh and also vastly more modelling
methods compared to patches.  A good example of the AG/D of NURBSs is when
using really complex models.  If you render the model based on mesh patches
you could end up with a massive amount of triangles.  With NURBS models you
can simply set the restraint angles and distances so it adaptively generates
the surface.

The other thing as I mentioned was the flexibility of modelling.  For
example with NURBSs it's very easy to just trim up and blend two surfaces
together seemlessly.

This issue has come up a few times in regard to POV-Ray and it seems there
is the same problem.  POV-Ray isn't a modeller, and modellers are needed to
make NURBS surfaces.  Making up the keyword description for POV-Ray would be
near impossible considering the number of specialised surface triming and
blend functions along with all the point and CV splines.  I personally have
no idea how it would be possible to make a tokinised description for NURBSs.

Someone also mentioned subdivision surfaces.  This has become an offshoot of
NURBS modelling and uses a method called "soft selections" (the term changes
from modeller to modeller).  Basically it works the same way only it allows
you to add weights to all NURBS points (even if it's a CV spline).  While
NURBSs already support this, subdivision surfaces do it differently because
they work on existing models (they "subdivide" <- thus the name; the
surface).

Anyway, I think I said this the last time the NURBS issue came up:  NURBSs
would be near impossible to impliment into POV-Ray and considering the
computational and programming overheads, it really isn't worth it.

Anyway, back to work, just thought I'd stop in.

--
Lance.


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Nieminen Juha wrote in message <37c3e249@news.povray.org>...
>  What are the advantages of NURBS (or should I say NURBSes?) over bicubic
>pathces?
>
>--
>main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
>):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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