Exporting curves to Alembic crashes other software when reading #49114
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Reference: blender/blender#49114
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System Information
windows 8 64bit
Blender Version
Broken: 2.77.3
1fe9d67Worked: (optional)
The curve import to others software will be report error, even cause crash
test.zip
Exact steps for others to reproduce the error
Download the test file and import to maya, or houdini, the some curve type will make report error or cause crash.
blender to blender:
Nurbs into Maya:
![}V5$~AO7B5KW]A)O2AKY1_7.png](https://archive.blender.org/developer/F338954/_V5__AO7B5KW_A_O2AKY1_7.png)
Poly or Bezier into Maya:
!- [x]R
2QT$~35E}7KPE{UK`E.png](https://archive.blender.org/developer/F338956/V_R_2QT__35E_7KPE__UK_E.png)![46HZM]9SDG3%`}OFX$V}F8P.jpg](https://archive.blender.org/developer/F338958/46HZM_9SDG3___OFX_V_F8P.jpg)
Have test with maya 16, maya 17 and houdini 15
Changed status to: 'Open'
Added subscriber: @Leroy-Xie
#50529 was marked as duplicate of this issue
Added subscriber: @kevindietrich
Setting to low priority since this will be a bit hard to solve without knowing how different software expect this data to be written. Alembic uses the Renderman conventions, and I already know that curves and NURBS are not as straightforward to export as meshes because of that (NURBS import is disable in Blender for this very reason). From the Maya plugin, control points need to be duplicated, but how this is determined is not documented, therefore I am afraid that a lot of trial and error needs to happen.
Added subscriber: @dr.sybren
I see crashing of other applications as a problem with those applications, and not something Blender can fix.
@Leroy-Xie Do you have a clear specification of how NURBS curves and surfaces should be written, in order to be compatible with other software? And since this report is rather old already, can you test what happens with a current version of Blender and whether this is still an issue?
The curve problem in Alembicto Exporting curves to Alembic crashes other software when readingAdded subscriber: @ChrisRydalch
Added subscriber: @mont29
Changed status from 'Open' to: 'Archived'
Time to archive this imho...
Added subscriber: @Andruxa696
I also have this problem. Blender 2.83
@Andruxa696 In that case I have the same question for you as I had for @Leroy-Xie: Do you have a clear specification of how NURBS curves and surfaces should be written, in order to be compatible with other software?
Unfortunately I do not have a clear specification and I do not understand the technical nuances. For my self I found solution to use only blender NURBS and create more vertices in it- then it works fine. But never export Poly or Bezier curves - then maya(version 2018 and 2019 ) crashes. Houdini 18 not crashes, but does not see Poly or Bezier curves correct. For Houdini the same solution - create blender Nurbs and add more vertices to it. Hope it will help somebody.
@dr.sybren I can only say that maybe we can convert and exporty Poly or Bezier curves the same way as NURBS curves, or convert it to NURBS before export.
For some of this bugs even no need to check it in other software - just export from blender and import it back.
last example where few Nurbs curves is part of one object - also exports incorect .
If I create few curves in one object in Maya - it exports to Houdini correctly , so it is not the limitation of Alembic.
I hope it will help you at least a little. Good luck and thank you @dr.sybren for you hard work.
alembic_curves.blend
@dr.sybren here is blend file with example - just export it in alembic format and import back. you will see what I mean. Thanks.
@Andruxa696 In that case I have the same question for you as I had for @Leroy-Xie: Do you have a clear specification of how NURBS curves and surfaces should be written, in order to be compatible with other software? And since this report is rather old already, can you test what happens with a current version of Blender and whether this is still an issue?
@dr.sybren seems you missed one of my previous message( message before I sent a file), I have answered on your question already. Thanks. If it is still unclear , I do not have a clear specification of how NURBS curves and surfaces should be written.
But please reread my long answer if you missed it.
I have tested it in last 2.83 and 2.9 (hash:
83304e4c22) builds . It still have this problem.Check file I have sent before.
For me it is not big error, I almost never use curve exports. Just want to help somehow . I tried to google some about nurbs curves and their technical specification in alembic , nothing found. maybe need to ask help in http://opensource.imageworks.com/ . I have downloaded source files on github, it seems they have example files and tests only in maya and houdini. Maybe we can ask them to help with specification. I can not help more, I am not technical enough for it.
Thanks, you did great job with alembic. Good luck.
The curves exporter certainly makes some assumptions that I don't agree with, and that I'll address at some point. This will be tracked in #76746 (which doesn't involve 3rd party proprietary software, so it's easier to tackle there).
Added subscriber: @kursadk
This is still an issue with Blender 3.4 Nightly and Maya 2022 The exported curves crashes Maya.
The USD export does not seem to export the curves properly, at least when I go with the USD route to export them, I do not see the actual curves in the viewport and they come as regular mesh object.