tomashubelbauer/3mf-zip-uncompressed

An experiment in seeing how no-compression ZIP file will diff in Git

3MF ZIP Uncompressed

This is an experiment in seeing whether repacking a 3MF OPC ZIP archive into a new archive with "store" compression (uncompressed) will make the changes to the 3MF file diffable and make the whole file a better fit for version control.

The process is as follows:

• Start a new project in PrusaSlicer with default settings
• Right-click the print bed and select Add Shape > Box with default dimensions
• Save the project as box.3mf
• Run unzip box.3mf -d box to extract the 3MF OPC ZIP into a directory box
• Run zip -r box -0 box to create a new archive, box.zip with no compression
• Turn off the lock next to the box properties Scale and Size
• Scale the box up twice the size by setting 50 for its Size on the Z axis
• Save the project again under the same name
• Delete the box directory to not clash with the unzip command
• Run unzip box.3mf -d box again to generate a new extraction of the project
• Run zip -r box -0 box to update the archive with no compression

At this point, VS Code will detect the ZIP archive is a binary file and will not diff it. It can be forced to view it using the default text editor, but even in that case it will not attempt to diff it.

GitHub will show the file as binary and will not offer a way to force-diff it. It does offer a link to view the raw file, but it downloads the file instead of diffing or at least viewing it in the browser.

Since Git detects binary files not by extension, but by a slice of the file's contents, it will always reject ZIP files because their extension is binary and further textual content (due to the store compression mode) will not make a difference.

It is possible to coerce Git into viewing textual diffs of binary files, but at this point, we've strayed too far off the default path and it will give more trouble than it is worth.

The conclusion, then, is that 3MF cannot be version controlled easily even by repacking with no compression. It's best to stick with unpacking the 3MF into a directory and versioning the contents of the directory. Or to use textual STL.