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trying to manage freecad documents with git
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FreeCAD git tryout

General idea

This is a playground with the purpose to try to manage FreeCAD documents with git. Basically, it contains folders which contain FreeCAD files and each FreeCAD file contains the geometry of one part.

The whole geometry of the model is supposed to be composed of all parts. So the idea is to load all parts in FreeCAD and create a part structure where the files of the individual parts are just linked into the assembly structure. To achieve this FreeCAD is run with the scripts from Peters Version Control workbench e.g.:

~/PROJEKTE/FreeCAD_git/freecad_git_tryout/Toyota_Yaris_-_freecad_assembly$ ../../versioncontrol-workbench/scripts/ body_in_white___________________________PID0

This script will require the Assembly3 workbench of FreeCAD in order to deal with the Links. Versions of FreeCAD containing this workbench can be downloaded here. Some basic ideas of how to collaborate with FreeCAD using git are also discussed in this FreeCAD Forum thread.

The user then works in the assembly structure which contains links of all parts. If he changes something the changes will go into the individual FreeCAD files since they are just linked. When the user finally saves the work only the files that have actually changed are saved.

The goal of this approach is that multiple users can work together on different branches of the same model and the amount of conflicts created is kept as low as possible. With this approach, a conflict only arises if users are making changes to the same part. So merging branches might become less painful.

The model

The model used here is derived from the public LS-DYNA models of the Toyota Yaris of the NHTSA. The geometry was generated using ANSA. Of course, this is not a real CAD model as designers would generate it. The purpose is to investigate/demonstrate ways of collaboration with CAD data when working in distributed teams.

Dealing with zipped FreeCAD files

This repository uses Zippey from here in order to better deal with the zipped fcstd files. (e.g. saving storage, allowing ASCII diff, ...)

In order to activate Zippey run the following commands:

git config filter.zippey.smudge "$PWD/ d"
git config filter.zippey.clean "$PWD/ e"

After applying the filters one has to switch bag to a commit before the fcstd files have been added (e.g. commit 98baa2110fdb09c7f5581ab133f45bacd6d9a3b5) and then get back to HEAD.

git checkout 98baa
git checkout master

Downloading the fcstd files from the website will only provide the unzipped content. In order to recover them you have to do the following: d < downloaded-file > recovered-file

Tries with merging

working with a single file on two branches

In this use case I created two branches: 001_single_file_simple_change_user_Alice and 001_single_file_simple_change_user_Bob in both of them I worked with the frecad file: Toyota_Yaris_-_freecad_single_file/body_in_white___________________________PID0.fcstd. In the Alice branch I changed the color of the part 51 in the Bob branch I changed the color of part 48.

When trying to merge I got this:

marko.thiele@jasper:~/PROJEKTE/FreeCAD_git/freecad_git_tryout$ git merge 001_single_file_simple_change_user_Bob
Traceback (most recent call last):
  File "/home/marko.thiele/PROJEKTE/FreeCAD_git/freecad_git_tryout/", line 198, in <module>
  File "/home/marko.thiele/PROJEKTE/FreeCAD_git/freecad_git_tryout/", line 192, in main
    decode(input, output)
  File "/home/marko.thiele/PROJEKTE/FreeCAD_git/freecad_git_tryout/", line 156, in decode
    (data_len, raw_len, mode, name) = [t(s) for (t, s) in zip((int, int, str, str), meta.split('|'))]
ValueError: invalid literal for int() with base 10: '<<<<<<< HEAD '
error: external filter /home/marko.thiele/PROJEKTE/FreeCAD_git/freecad_git_tryout/ d failed 1
error: external filter /home/marko.thiele/PROJEKTE/FreeCAD_git/freecad_git_tryout/ d failed
automatischer Merge von Toyota_Yaris_-_freecad_single_file/body_in_white___________________________PID0.fcstd
KONFLIKT (Inhalt): Merge-Konflikt in Toyota_Yaris_-_freecad_single_file/body_in_white___________________________PID0.fcstd
Automatischer Merge fehlgeschlagen; beheben Sie die Konflikte und committen Sie dann das Ergebnis.

When I extract both freecad documents and unzip them I can see that most differences come from Document.xml and GuiDocument.xml and unfortunately they are conflicting.



Some other differences are in files like DiffuseColor*, however, I suspect these are changes to different files.

The conclusion is that out of the box merging with git will not work with freecad files.

working with an assembly of multiple files on two branches

Doing the same thing as described above using the assembly with links to multiple files a merge was straightforward because the changes have been on different files. When opening the assembly on the merged branch the CAD model contained the changes of both branches.


Of course, this will not help if two persons work on the same part. This will still result in a conflict. However, as long as the work on a branch is focused on certain parts (subassemblies) of the model the proposed approach should make teamwork using git a lot less painful.

One possibility to help with conflicting parts might be to create an assembly containing both conflicting versions of the part. In this setup, the user would have to resolve the conflict manually, which is just the same as what does git if there are conflicting lines in one file.

creating and resolving conflicts while working with an assembly of multiple files on two branches

Note: This might lead to something...

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