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what is the diff between nurbs and subdiv?
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what is the diff between nurbs and subdiv? // New Users
Post by grymmjack // Aug 10, 2008, 6:21am
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grymmjack
Total Posts: 87
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it looks to me like nurbs is subdivided always, so i guess my question is really what is the difference, why have both?
do nurbs do something different than polys? for organic modeling is it better/more effective to use nurbs or subdiv? i know it depends on the what result you are after of course but.
the main thing i know so far: subdiv means while it appears smooth the underlying polys are very complex and many, so texturing for example a smooth subdiv persons face with one face texture would require mapping each poly face differently on the subdiv? or could a person create a single face for a texture from subdiv and still maintain the quality? i dont know.
is that what nurbs is for? how do you texture a nurb? is the texture restricted to faces, but there are no faces to nurb?
hrm. |
Post by stan // Aug 10, 2008, 6:39am
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stan
Total Posts: 1240
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nurbs are better for some things. you would have to convert them to mesh to texture them like sds though. I will be happy when/if nurbs makes it the workspace. they are better for piping, wire, many cast metal shapes in my opinion.
organics it's probably better to use SDS |
Post by grymmjack // Aug 10, 2008, 6:48am
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grymmjack
Total Posts: 87
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ah so you cant actually texture nurbs then. so it's like an intermediate 'cage' step between bezier curve and poly - i get it.
thanks for your help. |
Post by RichLevy // Aug 10, 2008, 6:50am
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RichLevy
Total Posts: 1140
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This is a very technical explanation of them.
http://en.wikipedia.org/wiki/NURBS
What does this mean? You can with nurbs modeling set up a profile and than set up a curve for that profile to follow. Every part of the curve can be modified in real time by manipulating just 1 point along the curve.
Subdivision modeling is still poly modeling with a nice smoothing algorithms adding along for the ride. While their are great techniques to modify the mesh in an area that may appear to act like nurbs, yet you are still editing along a poly by poly basis.
Similiar in some ways, though very different in application.
Rich |
Post by stan // Aug 10, 2008, 6:52am
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stan
Total Posts: 1240
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you can texture them but its the whole patch not faces with texture maps or materials |
Post by grymmjack // Aug 10, 2008, 8:18am
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grymmjack
Total Posts: 87
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when you say whole patch, is that the entire object?
thanks rich. didn't even think to look on wikipedia :)
i'm surprised you guys dont have a caligaripedia :) you have everything else, or have thought of it :) |
Post by spacekdet // Aug 10, 2008, 11:00am
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spacekdet
Total Posts: 1360
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when you say whole patch, is that the entire object?
Not necessarily.
By using the scissor tool you can separate parts of a nurb object into 'patches' and thus texture each part.
You don't have the poly-by poly control over texturing you have with a polygon based object, but you can indeed have multiple textures (http://www.spacekdet.com/iceboat/sailoutline.jpg) on one nurb based object. (http://www.spacekdet.com/renders/clinkers13c_s.jpg) |
Post by TomG // Aug 11, 2008, 4:54am
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TomG
Total Posts: 3397
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NURBS are like vectors or bezier curves in a 2D app, only they work in 3D. This means you have control handles to control angle of curve going into and out of a NURBS object.
NURBS eventually convert to polygons, and you have no control over the final polygons with NURBS. They tend to be polygon heavy too once converted.
SDS takes a low poly mesh and uses it as a control cage for a high poly mesh - the vertices and edges in the low poly control mesh "pull" on the high poly surface to define it. You cannot control angles in and out of curves using handles with SDS, but you can control it by adding edges etc. You have much more control over what the final polygons will look like (as its determined by the polygon / edge / vertex placement in your control mesh), and the results need not be as high poly as NURBS convert to - handy if you are making content for games for instance, but basically anything where you want curves surfaces but precise control of polys still.
I've always found NURBS hard to work with myself for going for an exact result, and found SDS much more intuitive, but each is suited to different things :)
I would watch the two NURBS courses to see how they are used, and compare tha with the Organic modeling course (older Model side SDS but still gives the idea).
HTH!
Tom |
Post by Igor K Handel // Aug 11, 2008, 8:21am
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Igor K Handel
Total Posts: 411
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Lofting nurbs gives a gorgeously smooth skin, pretty well instantly.. I love em.
Completely different way of working than poly modelling though. Like a whole seperate subject. Both Poly and nurbs have their strengths and weaknesses, things that they excel at and things that are better done with the other option.
SDS for me is somewhere in between.. The simplicity of poly modelling but an "almost" nurbs smoothness once sds added. Kinda nearly the best of both worlds, but faster than a nurbs patch building type workflow.
IK |
Post by grymmjack // Aug 11, 2008, 3:01pm
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grymmjack
Total Posts: 87
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thanks everyone. i think i have a good understanding of what NURBS are. i'll wait until i'm more at ease with TS before i do anything with them. |
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