A few weeks ago I was accepted into a beta program for an upcoming product release, Gravity Sketch, for the Oculus Quest (Virtual Reality headset). It's very intuitive to create 3D models in VR. The models created by GS are .obj and unfortunately, I can't seem to import them into MoI3d. Is anyone aware of a way to import .obj models into MoI? In many cases, I'd prefer to use a mix of GS with MoI for greater precision and there are many features that MoI supports that don't yet exist in GS (boolean subtraction being a big one for me).

Here's a video of the current GS Beta which should be released sometime this week: https://youtu.be/ZMqD8cKZCjY

Hi jon,

Please post a sample .obj file.

There is ImportObj script from Max, circa 2015:

http://moi.maxsm.net/files/

- Brian

Thanks Brian! I'll check these scripts out.
Attached is the character I made in GS from the video.

Hi Jon, the problem is that your . obj file contains 3D model data in the form of a faceted polygon mesh. That's a different type of 3D data than what MoI is designed to work with at modeling time (NURBS surfaces and solids).

You would need to use a polygon mesh editing program to open and work with that kind of data, not MoI.

You can go the other direction, starting in MoI and exporting .obj - MoI will dice up spline surfaces into faceted polygons and output those polygons to an .obj file. But it is not easy to go the other direction and automatically fit large smooth surfaces to an already diced up bunch of triangles.

There is an exception to that - if your polygon mesh is designed to be used as a sub-d control cage then you can use the sub-d converter which is new in MoI v4, under SubD > Create > From file.

However, your example .obj file above is not one that was designed for sub-d smoothing.

- Michael

At 100% after 12 minutes calculation crash : report was send to Michael

Hi Pilou, I would not advise to try and convert that file as a sub-d mesh. It's 108 different mesh objects, with approx 70,000 polygons all triangles no quads at all.

It is not structured to be used as a sub-d control cage and so it is not one that I'd expect to work well with the sub-d converter.

If you did want to try it you would need to make sure you have a very large amount of system RAM.

- Michael

So seems normal that this crashes! :)

With ImportObj:
In MoI3, hung up at 12,000 of 70,154.

In MoI4 beta, 0 of 70,154, error: Invalid index: 0 length = 0...

This type of model where the data is made up of a large number of little triangle facets, is not suitable for import into MoI. MoI is just not the right tool for opening that type of model structure.

You can export something like that out of MoI but not import it into MoI.

- Michael

Hi Pilou,

> So seems normal that this crashes! :)

Well it would be good if it didn't crash even though it's not expected to give you an actual useful result.

Probably the crash can be fixed for MoI v5. If it was a sub-d mesh which wasn't working right then that would be a higher priority to fix.

- Michael

Or maybe i had not enough hard memory...( 8 Gigas)

Hi Pilou, well even if it's not enough memory it's better to just bail out instead of crashing. It can be kind of difficult to catch every place where it can happen though.

- Michael

Hi Michael,

Thank you for your reply! Are there any conversion tools you might recommend that can convert the faceted polygon mesh into a format that is suitable for MoI (NURBS)? I'm honestly not sure if I'm asking the question properly. I played around with Meshmixer, but not sure if it can do the trick.

My 3D Printer splicer (FlashPrint) was able to import the .obj. However, when it imports it does report errors and attempts to repair it. Yet, it still was able to print the models which turned out decently (image attached).

I'd love to be able to exchange models between GS and MoI3d and if some conversion tool in-between is necessary, it wouldn't be a problem for me at all.

Thank you again!

Jon

Hi Jon,

> Are there any conversion tools you might recommend that can convert the faceted polygon mesh
> into a format that is suitable for MoI (NURBS)? I'm honestly not sure if I'm asking the question properly.

Well there are such tools but they are quite specialized - it's not like a matter of changing how things are just packaged up and formatted like many file format translations, you're instead talking here about a major change from one type of data (small facets) into a different fundamental type of data (spline CAD surfaces).

It's generally referred to as "Reverse engineering", if you do some searches on that you can find some software for it like Geomagic Wrap for example. You can also look for software for converting 3D scans into CAD models which is closely related.

But since it's a specialized field you'll probably find the software is quite expensive and will require a substantial investment in time to get good results, like in some software you manually guide the process by sketching a large patch structure on the faceted mesh.

That can be a feasible investment if it's an important part of your design process like you know you want to sculpt things in clay and then convert to a CAD model.

But for the most general case the polygon model data like you attached above is just not suitable for use as a CAD model.

- Michael

In general you must decimate your object and for Moi transform triangles in Quadrangles...
MeshLab is free and can makes that...http://www.meshlab.net

Thank you so much for your detailed reply, Michael! I did some more research and there is a "Pro" version of GS that appears to be able to export IGES (.igs) file format. I'm not sure if I'll run into the same issue, but I'm pursuing trying to get this option enabled in the beta to see if I can import models into MoI. If I have any success, I'll report back here. Thank you again for your support!

Best Regards,

Jon

Or more easy the free InstantMeshes https://github.com/wjakob/instant-meshes

So in Moi ;)

Hi Jon,

re:
> I did some more research and there is a "Pro" version of GS that appears to be able to export IGES (.igs) file format.

That's definitely worth a try. It's not automatically assured that it will help, it depends on what they put in the .igs file. Like for a sphere object do they write it as a sphere object in the IGES file or do they write out 1000 little flat facets for the sphere.

But if they remember that the object was a sphere and can write out that higher level representation then that could work.

- Michael

Thank you Frenchy, that tool looks pretty cool! I'll give it a try