Hi Sheik, one difficulty with doing this automatically is that a diamond is kind of a special case, in that it is supposed to be made up of planar facets.

So a conversion from mesh to NURBS where each polygon becomes one facet works fine for this case.

But often times polygon mesh files are intended to be a simulation of a smooth surface instead of one with planar facets. Trying to convert one of these types of mesh files into a NURBS object where each polygon becomes one little tiny NURBS plane will not work very well. The NURBS structure expects smooth surfaces to be made up of larger smooth surface patches instead of tons of little facets.

- Michael

Hi Michael,
Well I decided to get MoI, even if I fear this decision will keep me from taking the time to learn to use Rhino. I guess I will be using Rhino only for things I can’t do in MoI, but actually I will still primarily be using SketchUp.

I can imagine turning a faceted mesh surface into a one smooth Nurbs surface will need some serious coding. I wouldn’t mind an easy solution, and make the mesh becomes a big bunch of faceted Nurbs patches. I would only want it for reference, and maybe some Booleans.

Rather new to the whole Nurbs world I still don’t know exactly what you can and can’t do with them. Some simple stuff surprises me like; I can select an edge or face of a simple box, but I can’t move or rotate it (like I can in SketchUp). Is that difficult to implement with Nurbs?
I actually suggested SketchUp would add “Jell-O-mode” to the transforms. It would be similar to “soft-selection” transforms in some modellers: move (or rotate or scale) the top of a box, then define a distance for how rigidly you want the rest of the geometry to follow, and shaping would be like playing with jello Everyone has played with jello, right? No need for separate transform commands. (Somehow I think this would be easier with Nurbs, as you would need to add and reduce faces for this in a poly-modeller)?
Adding edges, moving them and push/pulling the new faces is a very fast way of modelling, which I would eventually like to see becoming possible in MoI.
Add the possibility of turning some faces (or edges) to be curved (tangent, G1, G2 etc.), thus turning the original surfaces and edges to a control cage, you could do very powerful box modelling (similar to T-Splines).
Oops, I guess I was rambling for a moment there, but this is such an inspirational product.
KIS, and think of new ways of making modelling more fun!

if you already have Rhino 4, then you can do many of your "Jell-O" transforms using Rhino's UDT functions. Also there are commands such as rotate face, scale edge, etc... This is not an easy thing to handle in Nurbs, because transforms will rip apart the seams in a polysurface. With polygons, transform functions don't have to worry about retrimming, tangency matching, and surface rebuilding as they do in Nurbs. Polygonal modelers just move vertices, which should be pretty easy. Nurbs require the object to be analyzed, rebuilt and redefined.

Also Tsplines is a great converter, but only for meshes that have a subd-friendly topology. If you try converting from Sketchup meshes, i imagine the results will not be what you hope for...

jonah

Hi Sheik, thanks for deciding to get MoI, I hope you enjoy using it!

One other thing you can do for bringing in a mesh as a reference is to use this tool: http://moi3d.com/resources#Obj23dmWireframe_converter which will extract out all the edges of a polygon mesh OBJ file and put them as line curves in a new .3dm file. Then that .3dm file can be loaded in to MoI and you will be able to see the wireframe of your mesh object in MoI as a reference and snapping guide.


> I can select an edge or face of a simple box, but I can’t move or rotate it
> (like I can in SketchUp). Is that difficult to implement with Nurbs?

It is much more difficult. Often times in NURBS the edges you see are "trim edges" with a larger surface underneath them, which means that the surfaces that make up your model often don't have their points aligned at the shared edge. See this FAQ answer for some more explanation and illustration.

This structure basically means that you can't pull things around by their edges (except in the case where the surfaces are actually aligned and end naturally at a common edge), but it is also the same structure that makes NURBS work much better than polygons for booleans and cutting operations. When you do repeated cuts on a NURBS object, it keeps the same underlying surface as a single big sheet and just new trim curves are calculated.


For Jell-O type squishing like Jonah mentioned the best solution currently is to take your objects into Rhino v4 and perform the squishing in there. You can move objects back and forth between MoI and Rhino quickly by doing Copy and Paste between them.

- Michael

I just found this. SpaceClaim looks like SketchUp on Nurbs. I hope we will see something like this in MoI 2.0 ;).
http://www.spaceclaim.com/Resources/SpaceClaim-Videos/SpaceClaim-Demo.aspx
Sheik

Hi Sheik,

> I hope we will see something like this in MoI 2.0 ;).

Nope, probably not - it takes quite a bit of extra programming work to do this kind of "history free editing" type stuff.

It's also fairly specialized for mechanical design type work, and MoI is not as exclusively focused on mechanical part design only.

If you need those kinds of SpaceClaim-like functions, your best bet is to buy SpaceClaim to do those operations.

SpaceClaim has good support for the .3dm file format, so it should work well to use MoI in combination with SpaceClaim as well.

- Michael