Skinning problem - combining curves for fairly complex surface with openings?

 From: Mike (MIKE1138) 20 Jun 2010  (1 of 10)
 Hi folks, I have a huge problem with the network of a surface. I think that the curves are not correctly intersecting, since I can only get one section of the intersecting curves to "surface". I am pretty sure that I don´t have enough curves defining the surface, and that the curves are intersecting with themselves makes it hard for MOI to calculate the surface. I would of course "simplify" the set up, but when I open up the curves in the middle, the edges of the left and right side surface don´t intersect smoothly and I get a "valley" in the mesh. In addition to this, I´d like to know if there´s a function to weld curves together into a mesh? I haven´t worked with a full fledged nurbs modeller before, I love it, but still have to figure out a lot. Any help in this matter would be highly appreciated! Thanks in advanve, even for just having a look at my problem! Michael EDITED: 5 Jul 2010 by MIKE1138

 From: Michael Gibson 20 Jun 2010  (2 of 10)
 3624.2 In reply to 3624.1 Hi Michael, the way Network works requires a fully regular grid layout, which means that all the curves can be flattened down into a 2D grid pattern. It's kind of similar to how curved latitude and longitude lines on a globe can be mapped to a flat 2D map with horizontal and vertical lines for each of them. If you have something like this curve in yellow here: Then you can't have something that only crosses it by some partial amount like this other one here: What will happen in your case above is that some of the pieces will be considered be excess portions hanging off the end of the regular network and will get trimmed off. To make a network you need to have a more regular grid pattern to the curves, more like this: The curves should be clearly separated into 2 different groups (like latitude and longitude), and each member of one group should cross over all the curves in the other direction. > In addition to this, I´d like to know if there´s a > function to weld curves together into a mesh? You mean so that you could pull around intersection points? No, that's really trying to process things more like a polygon mesh modeler would work. Really the strongest area of NURBS modeling is when you are generating shapes and cutting things from 2D profile curves rather than a big bunch of curves swooping all around in 3D. Also if you do have some 3D curves, you generally want to make more broad and simple surfaces from them and use booleans and trimming to put in some kinds of cutout details, rather than trying to build surfaces directly around hole outlines. Frequently I see people with a polygon modeling background try to build things in a more "patch by patch" method with building surfaces that hug around a hole, rather than the NURBS way which is to make a big broad piece and then cut it. Do you have an image or drawing of the model you are trying to create? That may help me to give you some more specific tips, but if your model has a lot of freeform nature to it and is not easily described by 2D profile curves, that could very well put it in a category of things that are more suited for sub-d/poly modeling with its focus of tweaking 3D mesh points around, rather than the profile curve driven strategies that are the best fit for NURBS. - Michael

 From: Mike (MIKE1138) 4 Jul 2010  (3 of 10)
 3624.3 In reply to 3624.2 Hi Michael, thanks for the reply! Yes, I am one of those vertex and poly push n pullers ;) And I already guessed what you told me, but tried anyway :D So, the "correct" (if there is any) way would have been to first start with a basic shape and then "chisel" away and add material. I attached my result so far, but my test version ran out before I was able to finish the project. No big deal since I did a poly version in another app, but still would have liked to have brought the project across the finish line. If you have a look at it, let me know what you think ;) Thanks, Michael EDITED: 5 Jul 2010 by MIKE1138

 From: Frenchy Pilou (PILOU) 4 Jul 2010  (4 of 10)
 3624.4 In reply to 3624.3 Cool model! (Colors are mine :) Seems curious : position of the model to the general gride! Mirror gives open intersections (I don't know if you want that) EDITED: 4 Jul 2010 by PILOU Attachments:

 From: Mike (MIKE1138) 4 Jul 2010  (5 of 10)
 3624.5 In reply to 3624.4 Yeah, I know, I was kind of looking for an instance object to mirror the parts and then work on the model, but when I did not find one I just started modeling away without caring for the model not being aligned to the center axis of the modeling area. I had a huge problem with connecting, joining, welding the surfaces, and if I´d start again I would really start with a primitive and then building up the model from there. As written before I was not able to finish the model, since my 30 days were up :( Maybe I´ll continue when the next demo version is available for 3.0 or so ;)

 From: Michael Gibson 4 Jul 2010  (6 of 10)
 3624.6 In reply to 3624.3 Hi Michael, > So, the "correct" (if there is any) way would have been to > first start with a basic shape and then "chisel" away and > add material. Yeah, but that method of "build a larger basic shape then cut it" is particularly what you want when your surfaces have a more irregular boundary, like if some pieces are shaped pretty differently than others, or there are things like notches or holes cut out. But if your model does decompose well into strips, then building it strip by strip is fine. With NURBS you just don't want to try and build surfaces around what looks like a hole - instead you build a full sheet pretending that the hole isn't there, and then cut out the hole with a trim or boolean operation. That's one of the major differences with NURBS modeling versus polygon modeling since in polygon modeling you usually try to avoid booleans, while in NURBS modeling they are usually more of a primary strategy. It look like you were making some good progress on your model! - Michael

 From: Mike (MIKE1138) 4 Jul 2010  (7 of 10)
 3624.7 In reply to 3624.6 Michael, thanks for the comments! Just as usual, old habits never die (easy) So I started wayyy to complicated by modeling like I usually do. And yes, almost there, but then time ran out :cry Ah well, maybe I´ll revisit it and finish it one day. What kind of really bugged me was that I could not figure out how to weld the various surfaces at the edges, leading to a bad polygon flow and of course an open mesh on export. Any tips on how to do that properly? Thanks, Michael