Yes, the .bak is a fully-fledged Rhino file, just with an extension .bak added. As son as you remove it, it’s just a normal Rhino file. You can continue to use it as any file.
Why you have a .bak and why you found your data in it…
When Rhino saves a file, it does the following:
- Saves the open file in its current state to the disk under a temporary name (like a SaveAS)
- If that is successful, renames the existing file (which is only current to the previous time you saved) to the file name + .bak (that is the backup file).
- Renames the temporary file created in step 1 to the original file name.
That system was originally designed to save your bacon in case something went wrong during a file save to disk. The backup file was deleted if the save was successful. Later they realized that leaving .bak file accessible to the user instead of deleting it might be helpful to some - with the downside of taking up more disk space and leaving .bak files everywhere - so it’s optional, you can turn that behavior off, and .bak files are no longer left on the disk.
I guess you can be glad today that this option is on by default…
Glad you recovered your hard work!