I’m not quite sure if this is the right forum: Its about Modelling, yes, but its also Discussion about a blender feature…so…I’ll leave it here for now.
My question is this: What are nurbs used for? I here people mention them in regard to construction or buildings sometimes, but I don’t quite get what they’re good for. They seem very imprecise to me and hard to work with.
So can someone fill me in on what the deal with NURBS is?
Not withstanding LC’s quote from the wiki . (Because I’m guessing you are more intersted in why Blender or any other 3D software might use NURBS)
NURBS stands for Non Uniform Rational B(asis- thanks LC!) Splines . It is a method of representing curved surfaces according to a precise mathamatical formula . As opposed to mesh surfaces (like the catmill-clark subdivision Blender uses) NURBS surfaces are more accurate in what it describes in CG space - it’s “discription” of an object can be used for CAD/ design purposes much more accurately . A mesh produced ala subdivisioning is not very “true” compared to NURBS - for example you can discribe a mathamatically “true” circle in NURBS with just 4 control points, while in a subdivided mesh you can only approximate it with only 4 (or even 360!) vertices . NURBS was/is a method of discribing surfaces that has “better” math for certain applications - i.e. for architects and manufacturers but isn’t used much in the CG film/FX anymore since the advent of mathamatical formula for sub-divisional surfaces by Catmil-Clark in the early 90’s (well that’s when his work started getting infulential anyway) . Sub-d surfaces are/were (I think?) less taxing on hardware because it’s calculations are done after the fact where as NURBS surfaces have to be calculated in time . Because of this a lot of 3D apps geared for CG film production “switched” to producing a pretty good toolset for sub-d modeling (like Blender) and often neglected their devolopment of a NURBS toolset (Maya is a stark exeption to this) .
The NURBS toolset in Blender are - for people like me - pretty weak . But You can still do stuff with it (and like I said above it is more accurate in discribing surfaces then any sub-d mesh) - it’s just that you need to play around with it more then just downloading tutorials (not that there are any) . Figuring out the starting points and the number of control points (of NURBS surfaces you want ot join) and the fact that you can adjust the infulence of those control points is probably the part that is the least documented … In fact you could model a human head as easily if not with more control using NURBS as you could using subdivisional modelling … but you would need to reconfigure your work-flow to figure out (like a lot of things in Blender) how to do it well . For example to do the above you’d need to figure out approximately how amy control points you might need to accompish tha task above and way beyond the 12 control points that the standerd 9 square grid patch surface given as Blender’s default when you create a NURBS surface or a circle (this of course is very inflexable compared to doing the samething right now using sub-d procedures) … But it isn’t totally hopeless dispite the lack of documentation about it … Like I just learned tonight that you can assign a new starting point for a surface ala a context menu I had never used before … Of course there’s always using NURBS for making interseting continuous surfaces with curves/paths ala Graybeard’s great vid tuts (though I wish he didn’t refer to control points on curves or NURBS as vertices - because vertices are control points only in a heuristic way (in a mesh) - i.e. you move it as the act of control where as for both bezier and NURBS control points have additional means of adjusting control over a surface/curve … ) .
But in general there ARE advantages of NURBS over just mesh espcially when it comes to to industrial design/CAD?architecture (just more accurate) and also it is easier to model some things using them then a regular mesh (like curved surfaces following a path/curve) and the mesh you get from NURBS is much more organized then most methods using mesh based modeling .
Right now Blender’s NURBS toolset is not very flexable and the documentation on what it has is next to non existant but it still can be used for some decent results .
I guess the Nurbana SoC 2005 integration project is dead unless someone else decides to take it up … Too bad really I looked at what’s there already and it’s about 90% done …
Hi Jason H,
the best example would be a real one. Try for 15 minutes to play for example with this http://www.moi3d.com/ and you will very soon discover miracle s of NURBs modeling 
Vert pusher, so if we learn to use NURBS and the technology advances, we could eventually lose the need for vertexes?