I noticed that in v4 beta there is a new button "SubD -> Create -> From file" that can load OBJ files.

I thought this is great because I can load an STL (converted to OBJ) and use it to reconstruct the object by snapping to the vertices of the STL.

I tried it with this object (shown in Blender):



And I got this:



That's a bit unexpected. Is this the expected outcome? Does this mean this new function cannot be used for the purpose I had in mind? What is its purpose then?

Maybe you must first use the free Instant Mesh for transform your OBJ in "Quads" then use SUBd
(or of course Blender)

https://github.com/wjakob/instant-meshes

You have also Import OBJ by Max Smirnov
http://moi3d.com/forum/get_attachment.php?webtag=MOI&hash=196c71c0e707b0c68f267a376fa30df3&filename=ImportObj.v.1.5.2015.09.10.zip

and / Or OBJ to 3md by Michael Gibson http://moi3d.com/download/Obj23dmWireframe.zip

Hi Andre, yes that is the expected outcome for that function, and that is correct that it is not intended to be used for STL conversion.

It's not a general purpose importer that can work on any kind of polygon structure, it is meant to be used on a polygon mesh that has been constructed as a control cage for subdivision surface modeling.

A sub-d control cage should be a lighter weight polygon structure that primarily uses quads, not a set of dense triangle polygons like you have in your model.

There's an overview of sub-d modeling here:
https://www.youtube.com/watch?v=ckOTl2GcS-E&t=4s

This function is meant to process the kind of quad-dominant polygon structures that you can see in the video. It is able to convert those control cages into smooth NURBS surfaces so you can use them as parts of a model that you are constructing in MoI.

It's basically a bridge between sub-d modeling and CAD. But it is specifically for sub-d models, not triangle mesh models. That's why it is positioned in the UI in a SubD tab and not in the general File > Open.

- Michael

Hi Pilou,

> Maybe you must use the free Instant Mesh for transform your OBJ in "Quads" then use SUBd

I don't recommend doing this.

That type of triangulated model data is just not a fit for MoI, it is better to edit that type of data in a polygon mesh editing program and not in MoI.

There is a type of workflow called "Reverse engineering" which is focused on processing high density discrete element data like that into CAD surfaces, but it is a complex area of work and isn't a task that MoI is focused on doing itself.

- Michael

It's for that i have writed "Maybe" ! ;)
It's a pity that the file was not linked for some test...

Sorry, here it is.

It would actually be enough to just get the vertices, that would take the whole "triangles vs quads" thing out of the picture.

THX for the file! :)

You have an import STL https://moi3d.com/forum/index.php?webtag=MOI&msg=9546.9
but suremlly some lines to erase by hands...
Not yet tested with your file...

I have made Import STL to Blender then export as OBJ without any regulates
(Blender doesn't love me so I use it just as gobetween :)
(it knows surelly make quads from triangles! Alt - J :)
So after InstantMesh..(i am not a specialist of it :)
So you can surelly have a better result of Quads following different parameters!

With SUbD inside MOi


With Import OBJ by Max Smirnov
So you can see that Quads regulates are not optimum from Instant Mesh with the regulates that i have used! :)


PS In fact for this particular case maybe you have better way to redraw it directly inside MOi!
(maybe 1 minute in slow process ;)

QuadMesher is pretty good for that kind or job, mush better than InstantMesh.
There is a bridge for the most common 3D package.
https://exoside.com/quadremesher/

I would probably clean the mesh a bit further to get a real cage Sub-D version, but it's a good starting point.

Those certainly produce aesthetically pleasing results but for the purpose of recreating the precise dimensions by snapping to the vertices they seem to be too inaccurate.

So you must redraw in nurbs over structure...

Hi Andre, probably the OBJ to 3DM wireframe converter would get you a result where you can snap to vertices. It will make a 3DM file that has line segments in it for every polygon edge.

- Michael