Objects disappearing in Blender 2.79?? DAG zero... not allowed to happen!

Component:Blender Exporter
Category:bug report
Assigned:David Bluecame


While doing some tests trying to implement image sequences in yafaray_v3, I had a serious issue in Blender 2.79 / Linux 64bit with yafaray_v3

Sometimes while manually changing from one frame to the next, I got this error message in Blender and all the objects in the scene dissappeared from the scene!!!

"DAG zero... not allowed to happen!"

During that test, I saved the .blend file and when I opened it it was completely empty!   This is a very serious risk and could lead the user to lose all their work in the .blend file.

I don't know if this was related to my tests with image sequences or if this is some kind of weird bug in Blender 2.79. I checked the Core code with some debugging tools and I could not find any reason for this to happen. Therefore it could be a new Blender bug or some weird bug caused by the Python interface between Blender and YafaRay.

This problem is difficult to replicate and will be even more difficult to diagnose/solve :-((  I don't even know if it's a YafaRay bug in the first place, but I could not see it happening with Blender Internal for example.

In any case, please be very careful and before saving your work take a look to see that the objects have not disappeared from the hierarchy. If they have disappeared, don't save the file!!!!



Title:Objects disappearing in Blender 2.79??» Objects disappearing in Blender 2.79?? DAG zero... not allowed to happen!


Ok, so apparently I'm not alone in this bug.

while windows sucks;do rm windows;pacman -S linux;done


Just did a git bisect on Blender itself and the problem went away when I reverted this commit

while windows sucks;do rm windows;pacman -S linux;done


Think this patch will fix it?

no_unlink.diff 1.48 KB

while windows sucks;do rm windows;pacman -S linux;done


It basically changes the Blender exporter to set do_unlink to False in the remove function in bpy.data.meshes. The commit changed the default value of do_unlink to True, which seemed to be the cause. Btw, I'm not really familiar with the YafaRay codebase, so I may or may not have done something wrong with the patch, but it seems to be working and this patch was based off of the information from the git bisect I did.

while windows sucks;do rm windows;pacman -S linux;done


Hello, pouar


Thank you *very* much for this!   I will check this asap and will let you know.


Status:needs review» ready to commit


This problem has been a pain, especially as I'm developing the upcoming v4 and this was causing me some headaches. Since I applied the pouar patch, it did not happen to me and I could not see any new issues, so I have prepared a small update for the Exporter:


This updated Exporter can be copied on top of an existing yafaray_v3 (v3.3.0) and will give you the following:

* Support for Image Sequences

* Patch for the DAG error (thank you very much, pouar! :-))

* A minor change in the camera code to remove an error message that appeared sometimes.

Please let me know if it helps. Unless somebody tells me these changes are not working fine, they will be included in the upcoming v4.0.0


Status:ready to commit» fixed


New builds with this problem solved here: http://www.yafaray.org/daily_builds/index.html?refresh=1


Status:fixed» closed

Automatically closed -- issue fixed for 2 weeks with no activity.