View Full Version : Sub-D N-gons OK in XSI?

06 June 2002, 08:51 PM
Hi folks

I'm a LW user who read in Dec issue of Computer Arts that XSI 2 has

"...a subdivision algorithm that's one of the best we've seen enabling you to use POLYGONS WITH ANY NUMBER OF SIDES WHILE STILL GENERATING CLEAN AND SMOOTH SURFACES."

Does this mean polygons with more than 4 vertices ? If so, I'll switch - can anyone advise??

Iain McFadzen
06 June 2002, 10:08 PM
Yes, N-sided polygons will work just fine, and as that article suggests XSI does a very good job of smoothing them.

06 June 2002, 10:20 PM

I'm surprised that this isn't bigger news in the CG community. Mathematically, this should make modelling easier by an exponential factor (or something).

XSI, here I come...

Iain McFadzen
06 June 2002, 08:34 AM
AFAIK it's only LW which still insists on quads, Max and Maya can certainly handle N-sided polys. XSI does seem to do a better job of smoothing polys with more than 5 sides, but IMO you shouldn't really be using polys with more than 5 sides anyway, other than as an intermediate part of the modeling process. It's much harder to predict how a 5 sided poly will deform, and that unpredictability increases as the number of verts on your poly increases.

06 June 2002, 12:02 PM
Aaaaah I shoulda known. You don't get something for nothing...
and despite the quad restriction, people still rate LW as one of the best SubD modelers.

I'll have the opportunity to use XSI soon, so it'll be interesting to compare.

Thx for the inform8ion.

06 June 2002, 01:58 AM
nsided polys are way old news, thats why its no big deal, yes most apps are still waitin for it, but Nworld had it over five years ago.

el diablo
06 June 2002, 07:20 PM
as far as I know there are only three algorythms for subdivision surfaces, Catmull-Clark, Doo-Sabin, and Loop Surfaces. Majority of 3D apps use one and some use two. Some software puts its own little name on them but dont be fooled they compiled it and didnt write it. So I would say majority of applications subdivde the same way. the key is to have an option on which algorythm you want to use. As for ngons, 5 sided smooths better than 3 sided. Let the algorythm do the work for you....el diablo

Maya user migrating to XSI, go figure....

06 June 2002, 07:55 PM
Your right about the algorithms, and typically it is Catmull-Clark, or often doo sabin, rarely looped surfaces from my experience, but with in each algorithm is room for play and variation, especially when getting into nsided polygons, where Catmull-clark was originally designed for quads, it has to be altered to take this into account, and the way each app does it will slightly vary.

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