n-gons


#1

Hi

I’m totally new to Maya (I’m coming from lightwave), so I have some doubts about Maya sub-Ds (they are quite diferent from subdivision surfaces in lightwave until now)

I made a simple object (all quads) and then converted it to a sub-D, after this I see some “n-gons” on the object (actually I don’t know if those are n-gons or just a way maya uses to represent subdivision surfaces)

How can I avoid these?? Or… do I have to avoid it?

thanks in advance! :thumbsup:

here’s an image showing what I’m talking about:


#2

oh, and sometimes when I convert from polygons to sub-Ds or vice versa, the object seems to be duplicated, so I’m having to delete he duplicated faces one by one! This is really annoying! Am I doying something totally wrong?

thanks!


#3

maya software render = no
mental ray = yes and no

the idea behind sub - d’s in maya is to minimize the topology count when you are refining details in isolated areas

which is great for modeling , a nightmare for rendering

if you want to avoid n-gons you can use proxy modeling insted
or you can

when you render a sub-d in mental ray you will need to colapse you hierarchy to the highest level of refinement, which defeats the purpose, plus you will loose any hard edges you made

maya 6 has a normal map utility, i havent made it work yet , but depending on your detail you could use that with MR

seems to me like they where on to something with there pixar ver of sub ds
but they didn’t develope it enough


#4

Hi Wehrmeister

First, thank you! But I didn’t get it… at least I’m not sure If I undertood it well

I’m coming from lightwave, so in there, if you model an object “all-quad” (only with 4 sided poligons), and hit “TAB” (turn ON subdivision-surfaces), the result will be an sub-D object with ONLY all-quads (no matter the refinment you’re using)… it’s simple and easy…

in other words, you can model it entirely with polygons, and then convert to sub-Ds, preserving the original “all-quads” you have modeled in the low-poly model…

Now as I understood, in maya, I cannot do that?

I mean… with I model an object with ALL-quads and then convert to subdivision model, the softeware automatically will create a N-gon subdivided model?? If so, it’s a really bad thing in my opinion.

How can I do this:

when you render a sub-d in mental ray you will need to colapse you hierarchy to the highest level of refinement, which defeats the purpose, plus you will loose any hard edges you made

thank you very much !

PS: and sorry about my english, i’m working on it :slight_smile:


#5

maya’s sub-d’s and lightwave’s aren’t quite the same thing. i ran into similar confusion switching from lightwave to maya.

what your talking about in lightwave (tab) is done in maya with the ‘smooth poly’ tool. that will take your low-res mesh and approximate it to a higher poly, smoother version.

maya sub-d’s are a completely different animal that i don’t understand at all.


#6

The pic you posted distinctly shows a four sided face as a poly and what appears to be an n-gon in subd. However this is not what it is. If it is a quad in the poly mesh, it is a quad in the subd mesh. What you are seeing is simply maya’s strange way of displaying its subds. Maya will display these extra lines when it has to alter the subd topology from a simple quad grid format. What looks like an ngon is simply the quad face surrounded by slightly more complex topology, hence the appearance of additional subdivisions. If maya does not have to increase the subdivisions locally, it won’t. And that is what happened here.

To see how ngons will actually look in a subd mesh, add a tri or a 5+ face to your quad mesh and you will see a bunch of lines spidering around as the mesh compensates for the ngon.

Only quads can be rendered as subd in mental ray. You can solve this by as mentioned, collapsing the subd mesh (Subds>Collapse) which removes maya’s optimization, and essentially smoothes the subd mesh by 1 to remove any non-quad faces. Or you can simply use the poly cage, smooth, or smooth proxy that, and apply a subdivision approximation to the smoothed mesh (Windows>Rendering>Mental Ray>Approximation Editor), which will cause MR to render it out as a subd (I haven’t tried this yet, so i’m just assuming it will work).


#7

To understand the power of subdivs, download Silo 1.2 demo at nevercenter.com and try out one of its tutorial on the site. The idea of subdivs is to combine the best of poly and nurbs modeling. Subdivs are the most modern techniques of modeling. I think because the Maya implementation is not as friendly or as fast as Silo, that’s why a lot of us misunderstood why it is a tremendous way to model. The yet-released Modo modeler basically make the subdivs its mainstream method. LW way of doing things is outdated - you have to pull point by point (too many click and point) to model. With Subdivs you only target the localized area for detail. The other part you simply move and model them in block or shapes. To simulate the TAB key in Maya, you have to use the smooth proxy, which is not the same as subdivs. In fact in Maya 6, Alias made it so that you can toggle between the smooth and caged version of your model by Shift ~ key, thus imitating LW tab key.


#8

Hi guys

Thank you very much for the explanation! It’s very very useful for me as a beginner to this “maya approach” kind of modeling.

So as I understood, the best thing is to do if I want to model using polygons, but seeing “real-time” smoothed geometry, is to use proxy smoothing and in the end apply “smooth” and clear the model (delete the proxy model and mirror&merge the half) before rendering?

Oh, another thing… I notice that is not a good deal to convert between polygons and sub-D’s, but If I really need to do this there is a way to avoid the duplicated faces that appears sometimes before the convertion? (note that this happens only sometimes, I couldn’t realize exactly when and why it happens)

BTW: well, today I’ll to my first effort to model something from scratch in maya using polygons and smooth… I’ll post it here for you guys to help me with the proper approach

ROCK: Silo is a WONDERFUL tool… the only bad thing is that it’s not compatible with MAC :frowning: … and I use a powerbook… so let’s wait for Modo! :applause:

greetings from Brasil


#9

The best way is whatever you like/need. Smooth proxy is quite a bit faster personally than subd. Plus you have to be in poly proxy mode to modify subd topology which is dog slow.

My preffered method is either to simply model in unsmoothed, or apply the smooth proxy to one side, and leave the mirrored instance alone.

There is absolutely nothing wrong with converting between poly and subd. If your conversion settings are correct there shouldn’t be any problem. But if you convert from subd to poly, while in poly proxy mode, the poly proxy cage is not deleted, so you can end up with a bunch of annoying junk in your mesh.

Could you post some pics of these “duplicated faces” you get just before converting? That shouldn’t be happening.

Edit: They are working on silo for the mac
Will Silo be released for platforms other than Windows? Silo is initially being released only on Windows. However, it has been programmed with cross-platform compatibility in mind, and Linux and Mac versions are in the works.”


#10

Silo for mac is coming out next week - check the press release linked from the Nevercenter front page


#11

Silo fom MAC??? woow, now this sounds really interesting! :smiley:


#12

I know of a MEL script that can simulate the TAB key in LW :slight_smile:

http://stud.cmd.hro.nl/0547724/@uploads/3d/zzToggleSubDee.zip

The original script can be found on Highend3D, but I’ve modified the script a little bit. Original = when converted to subd, resolution was set to 1, when converted back to poly, edges were soft.

My mod: convert to subd, res set to 3, back, edges hard… like LW.

I have set this script up at the a key… to bad TAB is not possible. I use it everytime I model!
I like this subd workflow better than smooth polygon when modeling.


#13

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.