I have to say that T-Spline is the best converter. I us eit to convert only base shapes. Now I'm working on this helicopter I made it in Nvil (3 hoours work) and now convert it to MOI.
As you can see cage is very tight, but T-Spline treat it very well! I use this tight cage becouse in Nvil as you can see I used Creas and to save these edges I have to make tight cage.

Looks liek I take the best from Poly and Nurbs. The fastest workflow made organic base shape in poly and then finish it in MOI.

Andrei, looks like there are about 30,000 triangles in the helicopter.

What is the largest # of triangles you have been able to process though T-Splines?

This is Resurf it convert OBJ to Iges, but you have only one Setting.

Step 1: load your OBJ mesh into software;

Step 2: click menu 'Surface> Blend mesh to NURBS' , the software will create NURBS surfaces from your OBJ mesh automatically. The NURBS surfaces are water-tight and exact G1 transition.

Step 3: save the NURBS surfaces as .igs file. Since the surfaces are water-tight, they can be sewed as solid without changing any geometry by other software.


http://www.resurf3d.com/Objmesh2solid.htm

Chrisd , really do not know did not tested this yet.

zarkow, I tested it, and unfortunately the result is not as good as T-Spline.

Viacad are working on the a add on tool to viacad which will have some mesh to nurbs tools, I'm waiting for the beta to have a play with it.

>>.. make some Converter to convert from Polygon models to Nurbs.

It's very interesting for me :) I'll think about it. But I won't promise anything at the moment.

Just came across this while looking for something else.

ViaCAD Pro 9 which was recently released includes sub division mesh modelling tools.
There is a future addon (coming) called Power Pack Pro which includes a convertor from mesh to nurbs. Looks like it does a pretty good job with even high poly models.
http://www.masterviacad.com/powerpack/page9/page36/page36.html

Unfortunately, it hasn't be released yet but sounds like they are about to start alpha testing.
http://forum.punchcad.com/showthread.php?t=4906&highlight=power+pack&page=5

Exciting technology anyway and worth keeping any eye on.

I may be a bit biased, but I think T-splines have the best subd to nurbs converter.. :)

The cheapest way to get this conversion right now is through fusion 360. It's free for students and hobbyists, and about $40/month otherwise. It can open OBJ files and export IGES, which should open in MoI without issue.

Hello,

T-splines along with the VSR (now Autodesk) tools for tweaks is a great combination. Hoping TS v4 for Rhino comes out soon, it makes round trip very easy being able to directly copy between applications.

T-Splines, PowerSubdNurbs, and other "converters" that have been referenced here are quite limited in the number of polys they can process into a nurbs surface. These tools are intended to be able to manipulate a nurbs surface based on a polygonal "reference" surface. The "conversion" is a by product.

If anyone has found something that can handle millions of polys, please indicate what it is. In my experience, the only applications that can fit a nurbs surface to millions of polys are Geomagic and RapidForm.

I am particularly interested in Resurf3D with their RhinoResurf application, which looks like it can handle more polys. Unfortunately I have not been able to test it because the Rhino trial and the RhinoResurf trial don't play well together.

Hello,

The last scan mesh I imported into Rhino (a few days ago) was around half a million polys. Using a combination of T-splines and VSR Shape modeling I was able to take that very organic 20MB surface and end up with a watertight STEP file around 340K in size with deviation of less than .1mm, well within tolerance for the application. I would not recommend using the technique indicated earlier in this thread, that just leaves you with a jumbled mess of control points, highly unmanageable. Using a combination of submesh creation and proper T-splines and VSR surfacing tools will leave you with not only a much cleaner and lighter set of surfaces, it will allow you to modify those designs more easily.

OSTexo,

500,000 was the max number of polys for T-Splines if a recall correctly from a few years ago.

Has this limit been increased?

Some of the work I have been doing just can't be decimated down that far. I'm trying to find something I can afford that will do a reasonable job of fitting nurbs to a high poly model, and does not cost $15,000 or more.

Hello chrisd,

Don't try to convert your mesh to a T-spline. It depends on the scan, but I like to append faces and use the world retopology snap after laying out the general resurfacing plan. After some tweaking, adding and deleting edges and faces you are able to check your surface deviation within Rhino itself. In areas of detail you can go back and change density in specific areas, add creases, etc. In the end you'll be left with a much cleaner and lighter set of surfaces.

The thing that I have found is LARGE SURFACE VARIATION = LARGE NURBS MODEL. There does not seem to be any getting around this one yet. Tooling producers will cry if you tell them you want to give them a triangulated model, but the nurbs representation can be just as large, or even LARGER than the triangulated version. I fail to see in many situations where the nurbs is actually going to better to machine from where there is a lot of surface variation.

Hello,

I'm not sure I understand what you mean by large surface variation. I'd like to see a small example of what you're referring to.

Try Decimation Master of Zbrush before some exporting! ;)

hows this?

ZSurf and you will obtain a Nurbs surface!

http://www.kf12.com/blogs/techno/2007/08/zsurf/

Hi Frenchy

Yes, ZSurf can do this for low levels of detail or debossing a logo, but really is not useful for more complex reliefs. It also does not import 16-bit greyscale files if I recall correctly.