Editing imported files

I have someone that sent me some .3dm files from Rhino4. I want to modify the file but when I import it it is just a mesh and cant be edited.Is there a way to save a file so that it can be uploaded into a different PC as a polysurface that can be modified?

Sadly, no.
It’s easy to make a mesh from a polysurface.
The process to start with a mesh and make a polysurface based on it, is called Reverse Engineering.

So when a file is saved as a 3dm file it is converted into a mesh? If that is so why can I edit files I have created and saved as 3dm files? Am I only able to edit files that I create myself?


No, you were just for some reason sent a file with just meshes in it, unless the NURBS are locked or hidden.

OK so how would you send a file with all the information in it.The files were labelled as .3dm files

As @JimCarruthers says, a 3dm file can have meshes or nurbs inside, in your case it only has meshes apparently. the process to turn into nurbs is not easy or automatic, if the model is not complex, the best option is to remodel it using the mesh as a reference in space.

Well what the person on the other end has to do is hard to say, it’s like “Why isn’t it NURBS? This makes no sense?” Tell them to send you the actual surface data.

Your data supplier may not have used Rhino to create the data, but rather a program that only creates meshes but allows the designer to export them as a Rhino .3dm file. A dialog with your supplier is in order to sort this out. If it turns out that the original data is from a program that only does meshes, then Deigo’s suggestion is probably the best option.

Thanks everyone.The sender said he used Rhino4 .I was hoping just to tweak the files.He wanted me to print them on my Form2 , but a couple of the parts are too thin to print well.I guess I can ask him to save the files and send them again with the NURBS data.Is there a setting or something in rhino4 that he would need to use to make sure the .3dm file has the NURBS information.


if it was made inside rhino 4 using the common nurbs tools, doesn’t need any configuration or special setting, just save it as 3dm; step; iges; x_t format should work.

I gave up.Every file he sent had only mesh information in it.I guess maybe he saved his file after he had done a mesh conversion and deleted the NURBS data?

Or maybe there never were any NURBS to begin with - he might have just downloaded something from the .net or imported it from another program that only makes meshes…

Any off layers, or hidden objects in these files?


no hidden objects or layers.Is it possible when he saved the files as a 3dm he saved it just as a mesh and the NURBS data was lost.

That’s not really possible. Either they have it in an original file or it never was a NURBS model.

Hello - it is certainly possible but if the objects were made as surfaces in Rhino the user would need to deliberately get rid of the surfaces after creating meshes. I suspect Mitch may be right and they were not made in Rhino only imported as meshes.


thanks everyone.Good to know.