[Bf-committers] blend files differ every time they're saved

[Jonas Eschenburg]

I noted that repeatedly saving the same project produces very distinct 
files.

Just try the following: Open some blend file. In my case, it was the BMW 
bemchmark from Blender's demo files. Save it twice using either "Save 
Copy" or "Save As". Then use LZMA compression (xz) to compare:

$ ls -l bmw*.blend
-rw-r--r--  1 jonas  wheel  3150509 16 Aug 18:45 bmw1.blend
-rw-r--r--  1 jonas  wheel  3150587 16 Aug 18:45 bmw2.blend
$ cat bmw1.blend | xz -9 | wc -c
  2975856
$ cat bmw1.blend bmw1.blend | xz -9 | wc -c
  2976400
$ cat bmw2.blend bmw2.blend | xz -9 | wc -c
  2978000
$ cat bmw1.blend bmw2.blend | xz -9 | wc -c
  5585604

It seems that most of both files is completely distinct. I'm not only 
trusting in xz here, I even wrote my own binary comparison tool. FYI, I 
disabled file compression in Blender User Preferences->File->Compress File.

Could somebody give a hint on what is happening here?

Jonas