Nurbs vs Polygon modeling - Better, or equal-but-different? 2005-05-20 - By hans_k
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I never got comfortable with polyhedrons and SDS, mostly use nurbs
unless it is just simple cubes or close to. I should say nurbs i a
higher level of modelling. as you handle the otlines and not every
little detail (SDS can be considered a high level modelling method).
One important difference is that nurbs are surfaces, not solids.
A good example of the superiority of nurbs is this:
You want a sphere with a elliptic hole in it. In polyhedron modelling
this is an obvious boolean case. But you will get disappointed. The edges
ov the hole will not become smooth, because of linear interpolation when
calculating the intersection edges.
With nurbs you project an elliptic curve to the sphere to make the hole
and the resulting edge is also a mathematical curve, absolutely correct.
I also like the way tS handles nurbs editing. It is very direct and
straightforward. The free example on:
http://www.caligari.com/products/trueSpace/ts5/Courses/nurbsdesign.asp?Cate
=Master
is a good demostration of that.
But nurbs is still a steph child in tS when it comes to a lot of things.
Booleans are not possible, and there is no support for symmetry. If you
would like to write a python script, forget that. There is no other way
to edit nurbs than the interactive way. And there are a lot of other things
you cannot do with nurbs but with polyhedrons.
In the same price category as tS there is RealSoft. It is mainly nurbs
oriented and have a very good way of handling booleans. Also you can use
some displacement mapping methods to create fur, grass and landscapes.
- Hans
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