OBJ Polyline Export Rhino V5 SR13

Hi Guys,

Currently at work, we have Rhino V5 SR13. I’m having an issue exporting a flat surface via OBJ and keeping the polylines / isocurves.

I have a requirement to export a flat surface to a program called Unfolder for MAC. It requires an OBJ and splits the file along polylines (or isocurves - apologies I come from a CAD background) into separate shapes that can be nested onto A4 pages and printed to create a cut and stick together template.

So the file I have got in Rhino looks like the following:

When I export as OBJ it meshes and the lines work. Problem is, I would like the mesh lines to line up at a predefined grid position (159.2mm x 246.2mm) so I can split in the mac program unfolder. As per below:

I have tried using contours, polylines, rebuild… everything looks fine but as soon as I export, the mesh settings override what I have done and I end up with the following:

I know its me lack of knowledge that’s causing this. Can this be done?

Thanks in advance, I have been banging my head against the wall for days now.

EDIT: I have attached the Rhino file if it helps.


hi, if i understand you correct you would like to apply a regular grid as a mesh over the entire surface? that might not work since it has to tessellate the roundes edges on the sides, which why it actually is triangulating it. Rhino 7 has a new command called Quadremesh but i am not sure if that would help anyway.

i suspect you could simply split the surface at the desired areas and join them back together which will help define the mesh structure a bit more. after meshing you can try to apply QuadrangulateMesh to clean it slightly up you can also delete parts and replace them with ngons if that helps. also you can use the command UnjoinEdge if you want to predefine openings. something you might be able to do with unfolder of course but i never used it i believe it works similar to pepakura which i had installed via wine.

but what exactly are you trying to do in unfolder? maybe i am misunderstanding the issue

Hi, Thanks for your response.

You are correct, unfolder is basically a native version of pepakura for Mac. I tried using wine but had little success.

The ultimate goal is to take the surface modeled, divide it into sections that fit on pieces of A4 paper, and layout using unfolder to automatically add Join ID’s. It can then be printed onto A4, cut and stuck together to recreate the original 3D surface. From there it can be traced on wood and cut using simple tools.

Basically I want to split the surface and create a printable template that can be traced onto wood.

I tried using the split tool to split the surface in Rhino, then I meshed each individual surface and then used the join tool. I ended up with the following:

I thought this would work but when I imported it into unfolder the mesh appeared like the following:

Screenshot 2021-03-31 at 09.49.42

I tried using the Quadremesh as you mentioned but still no look. Im not sure I understand the ngons part. Ill have to look into this, as I mentioned earlier, im from a CAD background so this kind of eludes me.

I have reached out to the developers of unfolder and what im trying to do is possible in that software, I just dont know how to get what I need from rhino. The sent me an example working file that I have screen grabbed below. I require the lines indicated with red arrows to be created in Rhino using a grid pattern of 159.2mm x 246.2mm (to fit on A4 paper) exported as an *.obj.

Hope this all makes sense, and I really appreciate you trying to help me.


Hi -

The information on the unfolder webpage doesn’t have any specifications for the .obj files that it can handle… You can export the surface and the lines from Rhino to .obj and use the NURBS format. Can it read that? Or, alternatively, export as meshes but include the curves - is unfolder then able to use those curves?