Roundtripping in Rhino

[gustojunk (Gustavo Fontana)]

hi @Joshua_Kennedy,

I think @Czaja is right here: the triangulation ruins any hope of productive round-tripping. Also we don’t have an importer yet, but it might make sense to have one?

@Joshua_Kennedy

You have to understand that Rhinoceros isn’t modifying the FBX/glTF/etc. file directly when you import it. Instead, it converts the entire file to a format Rhinoceros can understand (the Rhino document [3dm]). Then when the export occurs it’s converting the entire Rhino document back to FBX/glTF/etc.

Yes, I think that’s part of the problem. I do recall that Modo for example lets you work on files that are .fbx and make changes and save them, and they re-save over the same .fbx. I don’t know if it’s a UI trick and under the hood, they are doing exactly what Rhino is doing, or if they are in fact maintaining a common format file structure.

I recall having a similar conversation with @brian about doing this for Step, and his idea at the time was to store a nested block with the intact ‘importing structure/properties’ and an export update that same structure, or something like that?

Can we split this answer to a new topic: roundtripping in Rhino? …so we don’t hijack this thread?

Thanks,

G

[brian (Brian Gillespie)]

There are two parts of this question:

1. Are there losses when opening, editing, and saving non-3dm files?

The answer is “yes”. Nearly always.

Rhino works natively on Rhino geometry. Whenever Rhino reads a file of any kind, it is translated into Rhino geometry. When you save it, the file is saved as whatever you ask for. Losses in translation can occur. The objects may be in the same physical location, but may have had materials removed, or other data silently ignored.

This happens with almost every file format. There are settings in DWG and DXF files that Rhino doesn’t read. There are STEP entities we don’t read. I bet there’s stuff in FBX we don’t read, too.

So… the first answer is: Rhino will destroy data when you open and resave the file.

2. Please let me open, edit, and save non-3dm files

I guess the reason we don’t let you do this is because of (1), above. We’re confident that opening, editing, and saving the file is going to lose information from the original file. The moment you overwrite it, you can’t get it back (unless you have a backup, but let’s be real - we’re talking about humans here - we roll without backups all day long).

It’s a UI choice that when you open FBX and click Save, Rhino asks you to save a 3dm. And it’s a UI choice that it doesn’t ask you to overwrite your FBX and, potentially, destroy data that is there.

Could we change that? Of course. Do we want the support questions from people who destroy their data by opening a file and habitually clicking Save? Not really.