Hi Pat,
if you wish to turn your design into a real object via a wax carving mill or a rapid prototyping machine you will need to convert your Nurbs curves into a mesh first. For a mill this is then converted into a set of toolpaths by a postprocessing program, I am not sure about RP , out of my league!
regards Tim Blades.

Hi Pat,

In the beginning I too was a bit confused by all of this talk of "mesh".
For Jewellers wanting to export a design to be milled, an STL file is the "mesh" that we'd use.

But to do a realistic render of that jewellery piece, you'd need to use a different kind of "mesh" to suit those programs.
From what I understand it appears that for rendering, you'd use an OBJ file as that "mesh".

Hope this helps, Colin

Hi Pat, Colin - both STL and OBJ contain a similar type of polygon mesh object, but OBJ has more information in it that is more suitable for rendering, stuff like texture coordinates, more than 3-sided polygons, shading information, ... STL contains only plain triangle facets and no other types of information.

Basically though, there are different ways that 3D objects can be represented on the computer.

MoI uses a system called NURBS which works with mathematical curves.

A different system is a polygon mesh type object, which is a system that defines an object by using a larger number of small flat polygon facets.

Each different system can have their own particular advantages and disadvantages.

Polygons are used frequently in the entertainment industry - they are kind of easy to squish and deform for making creatures and face type shapes.

NURBS are used frequently in the CAD and manufacturing industry since having true curved shapes allows for a more exact definition of things like spheres, circles, cylinders, ....

It is possible to convert NURBS objects into polygons by dicing up the smooth surface into smaller facets - this is what MoI does when you save to an .obj or .stl file. It is not very easy to go the other way from a lot of small facets into smooth NURBS surface again though.

- Michael

You need a mesh for pretty much everything in 3D- from displaying Nurbs objects, for rendering, and for all stages of manufacturing and analysis. What you are seeing in the Moi viewport is not the actual Nurbs surface but a meshed representation of it. The true Nurbs object is infinitely smooth (in theory). In real-life this would be impractical to represent. So a mesh is required to define it in managable terms...

jonah