View Full Version : SubDiv surface for animation (what technique do the "Pros" use?)

07 July 2002, 11:51 AM
Hi there,

For a long time I've been trying to figure out the best way to model characters, I kind of concluded that SubDivision technique would be best. It also seems like the "Pros" use this technique a great deal. However if three-sided polygons are used it often (almost always) creates unwanted lines. This is also the case if less or more than four polygons are shareing the same point. These lines can be retouched in for example PhotoShop, but this won't work if you are making an animation.
I'm not sure if Softimage has a solution to this. On this page
I saw the picture I attached to this thread. It seems like Softimage doesn't have any of these problems. This is very simillar to a the wireframe model that Pixar created for the short movie "Geri's game". Is this true? Is it the program that I'm using that is the problem? (Lightwave)

Sorry I might not be able to reply to this mail within two weeks, I'm going on vacation. :) (I was just dying to ask this question).
Any thoughts/ comments will be greatly appreciated.


07 July 2002, 02:05 PM
Lightwave subpatch only works with tris and quads.

These lines can be retouched in for example PhotoShop, but this won't work if you are making an animation.
whatthe..? :surprised
Does anyone do that?

07 July 2002, 03:36 PM
Hi, erikals! I hope you will have/had a nice two weeks!

It's right: Softimage's subdiv algorithm can handle arbitrary-sided polygons.
But however...
For example the six-sided poly in the picture you've attached will result in a point sharing six
polygons after subdivison - which can produce quite nasty star-like artifacts especially
during animation (because of the tight angles!). There are other reasons I do not to use em...

I'd recommend getting used to modeling with quads only...
it's also relatively simple to change topology in a way only quads remain: (see attachment)


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Iain McFadzen
07 July 2002, 11:01 AM
I am quite happy using 5-sided polys where needed, they deform just fine and and can come in handy when terminating detail. I always avoid 6-sided polys because when smoothed they result in a 6-sided vert, and that's when you get that "flower" effect. I have noticed that XSI is a little better than Max at smoothing over arbitrary-sided polys and there are less visual artifacts, but as Ray pointed out it is so easy to fix N-sided polys there is really no reason to leave them in there and risk getting smoothing anomilies in renders.

07 July 2002, 11:05 AM
Thanks for the replies :)

I guess that answer my question, I though that other programs had some "magic" trick to fix it, but I guess maybe not. Back to basic. However I though Pixar used a simillar technique to this, but then again their program probably is better than anything else on the market. I will scan and post the image of wireframe of "Geri's" head when I get back to see if someone knows what they did.
Thanks again guys.

Thanks Ray. I will enjoy it :)
(Great models by the way)


07 July 2002, 11:14 AM
Hi Iain,

Yes I guess it's ok to use it some places, on certain areas of the model I think it would work fine. If it looks good it doesn't really matter :)


07 July 2002, 11:54 PM
why would youmake the model like that??

her eis a basic tenet to learn with subd:
USE 4 sided in all cases, whenever possible.

dont want to sound harsh, but that particular modeling structure is nonsensical from both a subd and animation viewpoint

07 July 2002, 12:41 AM
as Iain said, XSI can handle N-Sided-Polys a bit better
than max, but 5-sided-polys really don't matter.
They are very useful and sometimes needed i.e.
edge loops always create 5-sided-polys and this
mostly helps to create an realistic looking muscular
structure, contour, relief and silhouette.

I really don't care about 5-sided but 6-sided s*ck,
but as Iain said that ray said (:D): it is so easy to fix N-sided polys

08 August 2002, 08:32 AM
For the ones interested, here is a wireframe of Geri from the academy award wining short, "Geri's game" from Pixar. (Included on the "A bug's life" DVD).

(Scan from Computer Graphics World Febuary 1998).


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