Hi Burr,

> It seems there is an opposite conundrum here in that,
> NURBS would do the REAL object and Poly can easily
> replicate it to look somewhat real. Not the other way around.

It's pretty much a non starter to use polygons/subd for the "master definition" of an engineering model, because they are unable to represent conic section shapes like circles, spheres, cylinders, etc... You can get closer and closer to a precise sphere shape by using a lot of points, but it is inefficient to use a lot of points and still does not get a perfectly defined sphere. This is really bad for mechanical parts which tend to have lots of things like circular holes in them.

So that's the fundamental reason why NURBS is used for the "real" engineering tasks - it is a kind of unified object definition that can have exact circles, or also wiggly surfaces not just only one or the other.


Polygons in their simplicity though do give an easy ability to tweak and edit them, you are more free to grab a point somewhere in the middle of your shape and pull it up a little bit, or widen a piece a little bit by yanking points around.

The NURBS toolset does not tend to work like that and instead has more of a "construction" approach with building surfaces from drawn curves, booleans, cuts, fillets.

If you want to work more of in a "sculpting" type way of kind of nudging and tweaking your surface, then polygons work more for that.

If you want to work more of in a "drawing" type of way where your pieces are more defined by profile curves and you want to have things like fillets where pieces join, then NURBS works more for that kind of thing.


A lot of times organic modeling for stuff like faces and characters fits more with the "sculpting" method and mechanical and industrial type shapes fit more with the "drawing" and profile driven method.

An airplane fuselage and a car body are examples of man made objects that have a much more organic shaping to them, that can sort of put them on the "sculpting" side of the fence moreso as far as what is easiest to mess with them.

No matter which one is easiest for an individual person trying to whip out a particular model for rendering, for actual engineering "master plan" data the NURBS method is always the one used because it has that ability to have stuff like exact circles.


People build models for all kinds of different reasons though, if you're rendering the object and not constructing it, it is probably not a problem to you that your sphere is 0.05 units deviated from a true sphere because it is hard to see that in the rendering.

So the right tool for the job depends on a bunch of different stuff - what your goal with the result will be, etc...

- Michael