Dig into .blend File Corruption

I have a corrupted .blend file due to a single object that crashes Blender every time I try to open it. There are way too many models, collections to append them in a new file. It would easier to simply dig into the .blend folder structure and delete the offending object/mesh/collection. Since .blend is kind of like a .zip file, how do I get into it and delete the offender without being in Blender (since it crashes when trying to open the file)?

I don’t think you can do that…
.blend are in fact memory dumps, that can be zipped but it’s a direct copy of how data are stored in memory while blender is running , hence the fast loading of file.

You can try to append the scene, and see if from there you can find the corrupted object.
You can also append several objects/collections at once to find the one that cause the crash : you append half of the objects, if it crash then you append another half of that , until you find the culprit…
Quite tedious, but that also the fun of CG isn’t it ?

Thank you. I was hoping since the structure looks like folders when appending/linking that a simple ZIP is what it was. But alas, no such luck. Thanks for your quick reply and help.

Do you think a user-friendly backend .blend file content folder-tree editor is something the developing community could code so corruption offenders could be isolated and gleaned from a corrupt file that Blender itself is unable to open?

Interesting !

First, I think it’s quite rare to get corrupted .blend but of course it appends, especially when dealing with development versions of blender.
Making a tool as you suggest will be complicated because it has to carry all the part of .blend file loading and saving. In a few words it will be a stripped down version of blender, that probably would need to be updated as blender evolve. Also that doesn’t tells you what the corrupted data is. And maybe won’t allow you to save the file.

What could work is a script that try to batch import every object and make a list of corrupted ones.
But that will not covers every cases of .blend crashing on opening :
I had several issues with the VSE when there was a bug in displaying effects that made blender crash. I update blender one day and some files that have the current frame on a effect were crashing. The solution was to open the file without the VSE UI open , set to a frame without effect strip and go the the VSE to erase the effect.

If suddenly I run in that kind of issue I will probably try to fix it by myself before stat looking into a tool that can help me. So even if that solution exist people may not be aware of it because it doesn’t append that often.

Maybe asking broadly the community about their experiences will tell you if that can be an handy tool.

Anyway, have you recovered your file ? maybe once you’ve narrowed down the issue you can submit a bug report ?

The specifics of what might have caused the corruption wasn’t anything complex. I just scaled one object, and CRASH. I opened the .blend1 to recover (after having lost some work) and touched that same object again, and CRASH. I then pulled the even older file from the trash (thus having lost all the work I did before the first crash and .blend1 crash, which was A LOT of work at that point), and decided to delete that object without doing any action to it and saved right a way. I also opted to get rid of any other object that m…i…g…h…t… also be an issue. And now all is fine, but I have to do ALL the work over again. UGH.

I was actually surprised that this kind of crash happened with such a minor object. It wasn’t overly complex, no modifiers, no strange materials, quite bare bones (not bones). I have been using Blender as my primary ideas software for a lot of things where text is of minimal value, but spacial ideas come into play, even if not outright visual or 3D in nature, all because of the perceived file stability, and the ability to represent data more accurately and aggregately all without app subscription possibly locking me out of my work if I don’t continue to pay. I still will continue using Blender this way, but will have to have some extra backup.

Thanks for you help.

That’s indeed quite strange, I rarely had these kind of issues, have you still the buggy file at hand ? maybe it’s worth investigating a bit more, simplifying it and submit it as a bug report if nothing explains the crash …
When using the very first version of 2.8 I had some simple mesh that crashed once I went to edit mode because (using development version of blender ) some part of the mesh had been corrupted.
Another time (once again with development version) Cycles made blender crash if I put a plane in front of the camera at a specific distance. But generally Blender is quite stable, it can append that some object is linked to another using a driver or a modifier and that can trigger a bug , but generally bugs that make blender crash get a very high priority in the bug tracker. It’s always good to save / backup often but I don’t remember loosing completely a file, there is always some ways to recovers most of the work , worse case scenario, as you did…