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What's wrong with NURBS?
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What's wrong with NURBS? // Roundtable
Post by hemulin // Sep 27, 2006, 11:35am
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hemulin
Total Posts: 1058
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@hemulin:
Aw, polygons are way cooler than nurbs...and much easier to control :D
Why? :confused: If you can tell me a way to edit polygon points so that I can modify a curve in as simple a way as you can with nurbs then i'll use polygons. For example, all of my rc car roll bars are done in nurbs because I know that it is quite likely that somewhere along the line I am going to have to change the shape of the curve; that's why I use nurbs. Is there a simple way to do this in polygons?
PS - I created this as a new thread so as not to hijack madmouse's toilet thread :D (i'm prone to doing that sort of thing) |
Post by frootee // Sep 27, 2006, 11:51am
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frootee
Total Posts: 2667
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I prefer my pizza with canadian bacon, ham, and spinach.
The point is, seems to me that it is really a matter of preference.
Say, maybe this would be a good idea for a challenge then. Nurbs vs. polygons: create a particular object using one or the other.
Frootee |
Post by hemulin // Sep 27, 2006, 12:01pm
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hemulin
Total Posts: 1058
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Thanks frootee, I just want to know if there genuinely is an advantage of using polygons over nurbs, or if it like you say, just preference. :) |
Post by rj0 // Sep 27, 2006, 12:33pm
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rj0
Total Posts: 167
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NURBS were very popular when they first came out for 3D software, and they still are very big in the automotive and design industries. When SubDivision Surfaces (SDS) came out a bit after NURBS, a lot of 3D designers switched from NURBS to SDS because of the ability to easily build an arbitrary topology, even with holes (considerably more problematic in NURBS). Also (rumor has it, no expertise claimed here), it's easier to animate a low-polygon SDS model (with subdivision at render time) than a NURBS model. Another bane of NURBS modelers is seams between NURBS surfaces, which is not an issue generally with SDS. So generally anyway, it comes down to mainly which works best for you and your design. A couple of people have had good success with tS NURBS, until their models got complicated, and then ran into some difficulties. I don't remember the details.
If tS NURBS work for you, by all means use them. On some models they can't be beat. But, if you haven't already, try some of the same models with tS SDS, so as to get a better feel for which will work better for you for a given design.
Best of luck,
rj |
Post by Steinie // Sep 28, 2006, 2:31am
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Steinie
Total Posts: 3667
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There are two people that would know more than most, Dzigntist and Binkydognose. You know who you are.....;)
Whoa just had a flashback! Back to my Metaballs.... |
Post by frank // Sep 28, 2006, 2:56am
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frank
Total Posts: 709
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I never really used NURBS because in the end I always converted to a standard polygonal object (for animation), and there wasn't a way to get one with quads instead of triangles (which don't work well with SDS).
There are plugins now to de-tessalate but I've gotten so much into standard box modeling and such that I have stuck with that. |
Post by Jack Edwards // Sep 28, 2006, 3:42am
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Jack Edwards
Total Posts: 4062
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Actually there it's not hard programatically to extract the nurbs control points and turn them into polygon objects from the SDK. I was working on a plug in that did that, but I couldn't figure out how to calculate the normals properly and I couldn't figure out TS's memory management scheme so I had to make the plugin leak memory like crazy or the app would crash. :-(
I might have a partially working version of the plug-in on my harddrive somewhere... if someone wanted to help me solve some of the problems I was having I could make it available.
My personal view on nurbs is that they have uses in certain situations, like rendering perfect spheres and things that would require too many polygons to accurately represent. But for most things I think NURBs is an aging technology that has been replaced by spline based SDS modeling. Now if only TS had that everyone would be happy.... :D
-Jack. |
Post by Jack Edwards // Sep 28, 2006, 4:10am
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Jack Edwards
Total Posts: 4062
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Anothering reason why I didn't finish the project was that I discovered that if you right click on the convert Nurbs to Polygon icon and set the static res to zero you get a decent poly object. Follow that with an untesselate from the Polytools plug in set:
http://www.motbc.com/ForumStuff/Nurbs2Poly.jpg
Now what doesn't make any sense to me is that Caligari is already converting the control cage to polys to render to the display, you can test this by setting the manip res to 0 and display as mesh:
http://www.motbc.com/ForumStuff/NurbsMesh.jpg
I don't understand why they didn't create an option to just convert to this mesh directly...:confused:
-Jack. |
Post by Shike // Sep 28, 2006, 4:31am
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Shike
Total Posts: 511
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Ops, did my comment cause this thread? Sorry ! ;)
Granted, for some things, Nurbs are superior! Tubes and hoses in my Pregnoid and Workbench scenes were done with nurbs.
Biggest benefit there was that it's easy to reroute them later on, while a polygon version would be extremely timeconsuming to change.
For characters (my primary interest) polygons and subdivision is superior.
Think I recall that Gollum was a Nurbs model in the first movie, but they
switched to subdiv for the two other...?
One of the reasons to why I didn't like Nurbs was previous problems.( in ts5 or 6...?)
When having both subdiv and Nurbs in the same scene, I got visible cracks between the small surfaces in the subdiv models, and it didn't help to change the "Triangulation"-render setting.
When converting the nurbs to triangulated polys the problem went away...and also the biggest benefit of the nurbs...the changeability :(
However, in trueSpace 7 I can't recreate the problem....so it seems to be fixed (might of course have been a hardware problem with my old computer...maybe I was the only one with this problem?)
And therefore I change my statement: Nurbs ROCK ! :D
(though, still not for my type of characters ;)) |
Post by stan // Sep 28, 2006, 4:45am
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stan
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this was totally done with nurbs :)
http://www.caligari.com/gallery/imagesgallery/2003/May03/image.asp?Cate=GImages&img=11 |
Post by W!ZARD // Sep 28, 2006, 6:27am
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W!ZARD
Total Posts: 2603
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I don't think there is anything wrong with NURBS as such - I just found box modelling so much more intuitive. Box modeling also seems more precise to me as you can position your points numerically - plus there are other advantages with perhaps the mirror modeller being the biggest IMHO.
That excellent chopper picture clearly shows there is nothing 'wrong' with NURBS at all! |
Post by hemulin // Sep 28, 2006, 10:24am
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hemulin
Total Posts: 1058
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Ops, did my comment cause this thread? Sorry ! ;)
Granted, for some things, Nurbs are superior! Tubes and hoses in my Pregnoid and Workbench scenes were done with nurbs.
Biggest benefit there was that it's easy to reroute them later on, while a polygon version would be extremely timeconsuming to change.
Great, that's exactly what I am using NURBS for. I was just wondering if NURBS is the best way to create tubes you want to move later, from what everybody has said it is.
(Maybe I should have made my intro more specific and said nurbs curves or something like that - sorry :o ) |
Post by Jack Edwards // Sep 28, 2006, 11:00am
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Jack Edwards
Total Posts: 4062
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One advantage of NURBS that no one mention is that they come already UV mapped and ready to texture. :)
Of course since you can extrude polys along a path, as long as you keep your nurbs curve that defines the path, you can modify and recreate the SDS poly oject. So there's not that much difference between using nurbs or SDS to make tubes, pipes, and things.
Another way to edit SDS tubes would be to add bones and or use deforms. The advantage to the bones method is that you could make it straight to UV map it then bend it into shape for the image. ;)
-Jack. |
Post by e-graffiti // Sep 29, 2006, 12:21pm
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e-graffiti
Total Posts: 171
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A common workflow for modeling as far as NURBS are concerned is to make you overall smooth surface with NURBS then convert your model to polygons to do all the fine details. An example could be using NURBS to model a basic head shape, then convert the head to polygons and do the small details like eyelids, inner ear, etc... The strength of SDS and the reason SDS became so popular is because it solved the weakness of NURBS and polygon modeling. NURBS weakness is creating small details easily while polygon weakness is that to make a smooth surface you had to use many polygons. SDS filled the gap. |
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