Hi bmabam, the problem is that NURBS solids are designed to be made up of large smooth surface sheets, and not a zillion little facets that are arranged to simulate a smooth surface which is what you are ending up creating with this method.

Each surface in a NURBS model has some more overhead to it than each polygon in a polygon mesh model. That's because of various things like trim curves being tracked separately from the underlying surface, and each trim curve has both a UV curve to it as well as a 3D curve.

When used as intended for having broad smooth surfaces, that extra overhead is not significant and in fact the data size of a NURBS solid made up of proper smooth surfaces will usually be a lot less than a polygon mesh equivalent, with the NURBS solid also being a lot more accurate as well. For example a NURBS sphere made up of 1 sphere surface is a lot less in data size then a polygon mesh that is arranged to simulate a sphere.

But I can't recommend this kind of an approach where you're ending up with a single little tiny plane surface in the NURBS solid for every single polygon in the polygon mesh. That will only work very well if you have a pretty simple polygon mesh like less than 2000 faces, or if the polygons actually describe the model well like if you have all boxes or something that is actually supposed to be made up of triangles like maybe a gemstone.

What you probably have is something that is actually supposed to be a smooth surface, but instead you have 100,000 little facets that are arranged in such a way to try and emulate a smooth surface. That is not a good kind of thing to have as NURBS.

Usually for such things to get a good result you need to reverse engineer broader smooth surfaces from the polygon mesh data. There is some specialized software that can do stuff like that, check out this previous post for some links to some of those reverse engineering programs:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2469.3

- Michael

Thanks for the explanations. I understand the problem but for those of use that just do this for a hobby and the cash flow is always on the negative side, justifying a the money it takes to buy some of the software packages that it takes to do this kind of thing is pretty hard to justify. If there is a way to do these things on some type of limited basis like using TC and importing the IGES file, that will have to work for now. It takes a while to import the stl and it takes a while each time you do something with it. I can live with that for now and hope that someone will come along with the neet little free converter that has a fix it button.

Now for a real question. Is there an limit on the size of the stl file or # of facets in the stl file that can be imported or is simply a matter of the bigger it gets, the slower thinigs happen.

Also, a request. It would be nice if you would use more progress bars. For these operations, that take some time like import and export, I've sat more than once wondering if I should kill the program because it hit a dead end. To your credit, it always comes back when the operation is complete. A visual that things are still running is always helpful.

Thanks

Hi bmabam,

> Now for a real question. Is there an limit on the size of the stl
> file or # of facets in the stl file that can be imported or is
> simply a matter of the bigger it gets, the slower thinigs happen.

There isn't any one specific limit, it's more of the second thing you mention there where if you have a whole lot of polygons it will become heavier and heavier in data size and get slower.

I'd think you'd want to stick with something around 2000 faces or so.

It's just a not a good method to use though for heavier meshes, objects structured like that are just a very bad fit with the way NURBS work.


> Also, a request. It would be nice if you would use more progress
> bars. For these operations, that take some time like import and
> export, I've sat more than once wondering if I should kill the
> program because it hit a dead end.

Yup, in v3 I'm planning on working on this for importing.

For v2 there was a big step forward for export, there is a progress bar shown during the mesh generation stage now when exporting to a mesh file format.

- Michael