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Blender 2.80 crashes when opening a scene created by blender 2.7x with hierarchy duplication set to "group"
Closed, ResolvedPublic

Description

System Information
Operating system: Windows 10 Pro
Graphics card: RX 480

Blender Version
2.80, May 24, 01:38:50 - b3f96da2e605

Blender 2.80 crashes when opening a scene created by blender 2.7x that contains a hierarchy that has an object duplication set to "group" and is parented to a mesh.

How to reproduce
open attached blend file

Event Timeline

Bastien Montagne (mont29) triaged this task as Confirmed, High priority.

Fix for T57934 (rB7fe3d1e7d718) is direct cause of this bug (since you cannot have an empty as armature…).

I don’t think we should ever allow changing object type in our versioning code (besides when current one is no more valid)… A lot of Blender relies on some specific types of objects, going over all object's usages to carefully decide what to do in each case would be a lot of work, and a highly error-prone one too.

So I would rather go with second solution from @Sergey Sharybin (sergey) here (Show a warning about unsupported instancing detected.). Or add a new empty to instantiate dupligroup (when there is one!), but imho that case is a bit too much exotic to be worth the effort.

You can call it exotic, but it is what is used in an official demo file which is featured on blender.org and is used in official benchmarks.

P.S. I am fine with warning, but i am not fine with silent failure on such files. I had enough confusion about this to be explained.

Piotr (Lewiatan) added a comment.EditedMay 30 2019, 12:49 AM

I rather see this fixed or have a workaround of this problem, because I would be quite irritated being stuck in the outdated version of Blender because don't want to lose a large amount of work. As far as I've heard 2.80 was suppoused to be backward compatible. If DupliGroups were used by official Blender devs, they should work in 2.80 too. In my case, I had no idea I have had DupliGroup in my blend.file for god know for how long and I'd be happy to find out how to get rid off it.

@Piotr (Lewiatan) DupliGroups are still working with empties, which are the only type of objects where they were making sense in the first place. Having those on other object types was just a nice source of confusion. And 2.80 is not 100% backward-compatible, though we try to keep it that way as much as possible. Projects started with 2.79 should be finished on that version really, unless you understand and know what you are doing when switching to 2.80.

Bastien Montagne (mont29) claimed this task.

Over one week, stealing this to fix now.

It's worth noting that https://developer.blender.org/rB2fb54ef86e57598e4d27987066db7a06a8269413 appears to break the "classroom" demo (https://download.blender.org/demo/test/classroom.zip). Opening it now prints a few dozen warnings like:

Warning: Non-Empty object 'chair' cannot duplicate collection 'schoolDesk' anymore in Blender 2.80, removed instancing

and indeed numerous objects in the scene are now empties.

@Campbell Barton (campbellbarton), unless the web team is notified, or someone with the access to ftp actually does this, is not gonna to happen.

What's the best way to notify the web team?

Ok, guess you didn't poke them yet. So i've updated the archive.

@Pablo Vazquez (pablovazquez) , not sure if you want to make some further tweaks or notifications about demo being updated.

@Bastien Montagne (mont29). opening file from command line does not show any warnings.

@Sergey Sharybin (sergey) am getting bunch of warnings in the console… Fact that it does not show in UI is most certainly a separate issue related to how reports are working in Blender, looks like they are not 'ready' to show up during launch time for some reason…