Hole in a nurbstopoly object

[mary-poppins]

Hi,

I try to make a nice ship body, and I would like to make holes in it. I made the body with nurbs, then i convert it to poly. When I extrude some faces to make a hole in it, the smooth preview won't be nice, there are wrinkles in line with the hole. Here is the

Picture .  Could you give me some advices, how to make nice hole in a nurbs-like surface?

Thank you very much

[ryokukitsune]

 You are seeing this problem because your polygons are to bunched up. When you smooth your model you are dividing all the faces on the mesh and the verticies are averaged to the originals. The closer your geometry is the less space an average has to work with until it finally creates a flat area on a surface intended to be organic and smooth. Basicaly creating an edge with the surface normals. Even if your existing geometry has an average smoothness (to the shape you had with NURBS) in Polygons the surface is handled differently. Its handled by the position of the verticies rather than the form you are looking for.

 Working on a shape like this with polygons probably isn't the best idea because you're going to be battling this problem the more detail you put into the surface. The only way to deal with it is to either reduce the extra geometry or spread it out. To a limited extent you could work with less topology and the crease tool to preserve edges without adding any extra surface topology. For organic shapes that require extra detail edge loops help build up the geometry without affecting areas that don't need it. If you know how to “reduce” back down to a level where a smooth will gradient the frequency of the geometry back to where you need it. (that's a little cryptic I know but its the best way I can describe it)

 Another solution would be to read up on Subdivision surfaces or Nurbs Patch modeling. They are both basically the same thing. You create patches of geometry that have varying levels of detail without actually adding any extra topology to the surface. With SubDiv's the topology is automatically combined into one object but with Nurbs Patch modeling the surface is interconnected using history to create a contentious surface. Likewise the two can be converted so long as the geometry and topology is “working”

 using SubDivs to polygons you'd have to adjust for the level of details since it will create those patches I mentioned with Nurbs but nurbs to Subdiv's will combine the patches into one surface that you can work with more easily in other surface types.

[mary-poppins]

Thank you very much Ryokukitsune! I try it both ways (subd and patch), and I will come back.

Thanks a lot

[mary-poppins]

So here i am again, i have no much time nowadays, but i tried this:

ryokukitsune: Did you think of this procedure?

I convert the nurbs to subd, then make some division, the convert it to poly. Then I extrude some faces for testing, and it seems the shape remain nice

If I endeavour to model with quads, how can I achieve this shape/ or repair its wire? Because if I tried to modify this obejct (to replace Ngons), I think the form would be injured...

The nurbs patch models don't have UVs, as far as I know. How is it possible to make paintings on them?

[joojaa]

Just out of curiosity why do you even bother to convert it to polygons? Or why do you smooth the polygons, why not make sufficently tesselated nurbs models to begin with.

[mary-poppins]

Joojaa: when I convert it to poly in the first step, I couldn't treat the it (for example, when I insert edge loops, it modify the shape, and I coulnd't extrude the faceses symmetrically. Yes, you are right, I tried to convert it with options making more edges, and it works. I just wonder that it is the appropriate procedure if I want to make some small gadgets on a big shape, because the vertex/poligon count will be higher.

[joojaa]

I want to make some small gadgets on a big shape,

The question in it self does not make sense out of context. We talking sotheing that aims games market or is it going to be rendered out? So whet is it going to be used for, and how does the rarget rendering sytem work. Theese are all questions thet you need to have a answer on before you even start to contemplate on such things as poly count. Without context such musings mnake no sense.

So theres several ways to do this depending on whta your target is, but one of the more fundamental things to understand is that theres no added value for having the objects combined into one.

So if your targetting, mentalray, maya software, renderman or vray for example keep it as nurbs, theres no reason you can not extrude and round the edges as nurbs, the quality will be better.

If games, then you dont need to make the hole necceserily as geometry at all, but in either case dont make a square pattern on the surface but rethare a round areound the hole so the hole starts form a radial.

Likewise protryudions dont need to be Cut on the underlying surface for games and many of the renderers, tough not reyes renderers like prman. But thenagain you use nurbs all the way anyway.

PS: if you smooth DONT talk about polycount as smoothing makes your polycount SKY HIGH in thsi case smoothging makes n^2 or n^3 times more polys than your accounting for!

PPS: polycount is not really an issue in most things. Only take it as it is whan it is.

[mary-poppins]

Thank you Joojaa. I think I'm confused a little, because I would like to make it for only mental ray, but I wanted to do this that way as if it had been for animation (keep everything in quads). To practice making things with nice wire. But if I keep it as nurbs, I won't be able to texturing it.