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View Full Version : What is actually the point of NURBS patch modeling?


jack516615265615
01-19-2007, 08:20 AM
Hi -

I've seen in several books now lessons devoted to NURBS patch modeling, and I'm having a hard time understanding the idea. Furthermore, in each book they convert the finished model to polys after going through all that trouble with NURBS, seemingly defeating the purpose of using NURBS in the first place (since you lose the resolution independent smoothness). So what are the actual advantages of patch modelling over something like SubD's? Do any studios still use this workflow?

Thanks - Justin

fx81
01-19-2007, 11:55 PM
i believe its embedded in some studios pipeline too deeply. some big studios like dreamworks and ilm still use nurbs i believe. many other studios used it in the beginning and converted later.

jack516615265615
01-20-2007, 12:10 PM
Is there a good reason then to model something with patches only to convert it to polys afterward? Why not just start with polys and avoid the hassle?

BenDstraw
01-20-2007, 09:15 PM
maybe they want to tweak it with as much control as possible by using the nurbs or patch controls then further tweak it in edit poly to get exactly what they are looking for. but ive never made anything good in nurbs. so what do i know :wise:

PredatorGSR
01-21-2007, 05:23 AM
Can't speak for the studios, but for some stuff nurbs is easier/faster to model with. For example, modeling the shift boot in a car out of curves, or creating stuff like a car fender can be easier with nurbs. Not only that, but you get smoother even curves and don't have to worry about stuff like the vertices not being even.

That said, I don't really like nurbs myself, and use polygon modeling techniques for almost everything. For the shift boot on a recent car, nurbs were preferable to polys though, because I was able to create folds and wrinkles very quickly.

Butsa
01-22-2007, 01:09 AM
well i prefer NURBS patch modeling over poly modeling
because i can see what am i doing while doing it
i dont have to use smooth proxy or anything like that

for me nurbs are even easier to texture
NURBS modeling can achive perfect smooth lines on industrial models and stuf
but besides still images i wouldnt use nurbs at all

as much as i know ILM is still using Nurbs on every movie effect they made

Nii
01-22-2007, 02:36 AM
Actually I haven't had a chance to explore it much, but it would be nice if someone can confirm something for me.

In the XSI documentation, if you want to make clothing that can be stitched together (ala 3ds Max's cloth/garment making) then you must use NURBS. It can not be done with polys. Can someone more experienced in XSI confirm this?

dtoxxx
01-22-2007, 02:04 PM
NURBS always seemed very unintuitive to me.
But in the begining it was just THE way to do hi-rez models for film.

As I understood it, NURBS was the friend to modules like HAIR and CLOTH in high end apps like Maya. And generated perfect UV's to be used with HAIR and for texturing.
Since I don't care for NURBS I didn't try to keep up with it.
So I don't know how things are with them now except that I probably don't like them still.

jack516615265615
01-22-2007, 07:46 PM
I think NURBS is great for hard surface objects because they give you infinitely smooth surfaces that aren't possible with polygons (I prefer SubDs for characters). I find NURBS patch modeling to be a headache, and texturing these patch models to be even worse. So I can see why one would prefer to convert the patches to polys for texturing, but in that case, why not just start with polys? Can someone tell me why, in every patch modeling example I've ever seen, they convert the patches to polys at the end, therefore losing the one advantage of using such a tedious process (the resolution-independent smoothness)?

- Justin

Butsa
01-24-2007, 01:32 AM
well there are a few problems with patch modeling

for example when you have corner with 5 patches
texturing that can be a looooong proces because if that corner isnt on a flat surface its almost always visible
so for that kind of situations i am using projectors for texturing
with polys you dont have tose kind of problems
second when patching you have to make sure that every patch has same number of isoparms in both directions

so if you ask me that could be the reason for converting a fine patch model into polys
i hope i was a bit helpful

my english aint that good so if you dont understand something i wrote please send pm to me

cheers
marko

ManDay
01-24-2007, 05:38 AM
I have a question a bit off the topic: Can somebody tell me whether spline-modelling (surface-modifier) also exists in Maya?

dtoxxx
01-24-2007, 10:58 AM
I'm almost positive that it is.
At least it used to be anyway.

Leionaaad
01-24-2007, 12:34 PM
Can somebody tell me whether spline-modelling (surface-modifier) also exists in Maya?

Nope.
However, there are NURBS tools wich have some resemblance with the surface modifier (you are talking about 3DS max, right?).

Abouth NURBS in production: Latelly I started to study a little NURBS modeling and my conclusion is: NURBS isn't really suited for character animation (or anything that deforms over time), because of the continuity between the patches. So this is why they convert NURBS to polygons in the end.
Or I am missing something here, I am not sure...But for objecs that doesn't deform is an excelent approach.

BurningFencePost
01-24-2007, 12:45 PM
I have heard some say that patch models are tricky when skinned to a skeleton, you have less problems with polys

hive
01-25-2007, 05:13 AM
The T-Splines Maya Plugin was created to solve many of these problems with NURBS--there's no continuity or gap problems between patches because you can actually merge the patches together and get a smooth non-rectangular topology.

Models can be textured and animated using Maya's polygonal texture and animation tools. Read more here: http://www.highend3d.com/articles/features/20.html.

jclepev
01-26-2007, 05:10 PM
I believe that many studios (mainly for feature animation) still model with nurbs because of the use of hair, or propietary tools. That is the case of Stuart little, with all the fur, feather simulation. Without being too technical, it has to do with U-V space. (http://www.xsi-blog.com/?p=33)
I dont think that it has a lot of popularity in VFX market, unless something mechanical is involved

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