# NURBS: How are they used?

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?

NURBS= Nonuniform Rational B-Spline.

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) .