.obj export file error


I’ve a rhino model that im exporting as an .obj then importing into blender. when the file is imported into blender the model basically has no data (no faces verts or tris etc.) when im looking at the the .obj file icon in finder doesnt have the model preview on it either??? what am I doing wrong between model and exporting it as an .obj? is there something I need to package before doing so?

I have been having that issue for quite a while. Obj files are fine if exported asa polygon mesh objects, but seem empty when exported as NURBS. The file itself does contain data (opening it as an ASCII file) but nothing seems to display that as a 3D model. However Rhino can import the obj file and display it as it should be.

Perhaps a Mac issue? However I am able to manipulate obj files downloaded from other sources.

Is anyone having success with NURBS obj files on the Mac?

Do you have a sample 3dm file and the saved obj version set to NURBS? Also what app are you opening the NURBS obj in where it doesn’t show? If Rhino opens and shows the NURBS obj, the issue sounds like it might be the other app only supporting mesh obj.

Personally I only ever use mesh obj, the open format I use for NURBS is mostly Step 214.

Here is the simplest example I could imagine – a unit cube.

It doesn’t show anything viewable when previewed in macOS quick view, nor opening with Xcode, Reality Converter or a little viewer utility I just downloaded called Azul.

I have contemplated it being a macOS incompatibility but wanted to see if there was a solution. The reason I’m wanting to save as a NURBS version is I’m doing a bit of 3D art in Grasshopper and the result has 10000 cylinders – not too demanding when described as cylinders, but as polygons the output file is 2.5GB!

The ultimate goal is to convert my designs in to USDZ so I can use the iPhone’s AR features to display them.

Note that I was incorrect in my first post when I said the Mac would display models from other sources. I realised they will have been mesh versions.

Cube.3dm (1.5 MB) Cube.obj (2.4 KB)

Your Obj comes into Rhino again as NURBS so I think the variable that will determine what works is if the application opening the Obj supports the NURBS option. I looked up USDZ a bit and I don’t see NURBS support in a quick search. Just for fun, I checked the Obj import in Blender and only the verts come in if NURBS was used when saving it in Rhino. I also tested a new glTF export plugin in Rhino 7 (PackageManager command to find it) that is a work in progress as that was another format that I wondered about preserving NURBS for you. I couldn’t find a definitive answer on that so I just tried it in Blender as well and that gets converted to a mesh.

I’m not sure if this is helpful, personally I would look at optimizing the meshes (e.g. less polys, joining into a disjoint mesh) as I suspect you will end up having to be a mesh model at some point in your process. Good luck on the project.

Thanks for your efforts. I can imagine Rhino being able to import my exported file given it would speak the same language as my copy.

My suspicion is that macOS doesn’t support NURBS in obj files since the Finder only shows an empty scene when previewed, even before trying to convert to other formats.

If you are interested in what I’ve been playing with so far using USDZ (and if I can successfully attach it here) check out this AR video clip I did of a TASCAM audio interface I created from schematics, then projected using my phone on to a flat surface.

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