Hi, I have this OBJ file from a smartphone app scan. Originally it was 50,000 triangles but I reduced it in Meshmixer to 13,488 triangles. it opens instantly in Meshmixer.

I need to convert it to 3DM for Alibre Design but when I try to import it into MoI3D V4 it takes a very long time on my fast PC.

Any ideas?

Thanks.

Hi Andy, what method are you using for importing it into MOI v4, are you trying to process it with the sub-d converter or some other method?

Note that the sub-d importer is designed to work on a mesh that is configured for sub-d smoothing to be applied to it, so it's expecting things like all quads, edge loops, stuff like that. Your file is not set up like that you've got a high density triangle mesh which the sub-d converter is not designed to process.

In general high density triangle meshes are not the type of data that CAD programs are set up to work on directly. You might try the wireframe converter from here though:
https://moi3d.com/resources#Obj23dmWireframe_converter

But generally it is not advisable to try and directly use triangle mesh scan data in a CAD program, it needs to go through a rather complex "reverse engineering" process to have it converted into smooth surfaces used by CAD.

- Michael

Thanks however Alibre Design doesn't like the resultant 3DM file because it doesn't have any faces. :(

Andy

Hi Andy, yes that method will generate lines, not faces. I guess Alibre does not try to load curves from .3dm files.

CAD programs are not designed to operate on models diced up into tens of thousands of little triangles. CAD programs expect larger smooth surfaces.

So it's difficult to do what you're trying to do. The type of data you have obtained from the scanning is meant to be loaded into a polygon mesh editing program, not a CAD program.

The process of fitting smooth CAD surfaces to dense triangle data is called "Reverse engineering". Some info here:
https://wiki.mcneel.com/rhino/reverseengineering

- Michael

I started trying to recreate the key surfaces, but this is very fiddly and frustrating so I'm probably giving up on this project. :(

Andy

Decided on this approach then export to Alibre Design and re-draw a new volume to match.

Andy,

The way to do what you want to do is import the original mesh file (50,000) into a poly-modeller (blender)
Build a new model around the original all in quads and go as low poly as you can and keep the shape (using the subdiv modifier to help)
then you can import the new lowpoly model into Moi using the subdiv import.

Val

https://www.youtube.com/watch?v=4sC131_cO6U

Maybe help you this feature in Rhino 8.
Mik

Hi Andy,

I don't know if -what I want to suggest- will be helpful for you or not!

>when I try to import it into MoI3D V4 it takes a very long time on my fast PC.

I also once tried to import an Stl in MOI so, I opened Blender and saved the Stl file as an Obj but it took a lot of time to be imported in MOI and it never imported it!

Then I realized there were overlapping points (vertices). so, in Blender I did
something used to be called (removing doubles!) and then saved the file as an Obj. This time I was able to import it in MOI without any issue!

I don't know if you checked your model for double vertices or not but I recommend you to check that before importing it in MOI.



I was able to import your attached model in MOI as an Obj but only after I removed over 4000 excessive vertices using Blender.
Hope this method will help you.

-Psygorn

Thanks psygorn - very interesting! I will give that a try! Andy

Hi Psygorn,

error message appeared when I tried to answer for your private message. You disabled receiving private messages probably.
Mik

Hi Andy,

in addition to Michael's post, here is an reverse engineering approach in Geomagic Freeform:

1- Create a smoothed out, healthy mesh to work with in GOM Inspect.

2- Create a thickness to the mesh in Rhino, otherwise it won't import into Geomagic.

3- Draw boundary lines for your patch layout. These lines can be "fitted" to the voxel mesh.

4- Create patches step by step.

5- Export patches as STEP files, so it can be used in parametric CAD Software.

This is how i worked in my former company. Please remember that Reverse Engineering is very time consuming.

Best regards

@ PILOU:

The " Skin Surface" Tool is amazing.

I tried it out some years ago. Unfortunately, they don't sell it as a standalone function.
Otherwise, it would be a great addition to one's toolbox.

QUICKSURFACE is also a good option, it costs around 4,000 dollars.