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Alembic - exported file does not keep collection offset
Open, Confirmed, MediumPublic

Description

System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.82 (sub 1), branch: master, commit date: 2019-11-05 18:12, hash: rB0bee94f920f9
Worked: (optional)

Short description of error
Alembic files does not keep the collection offset data when exporting collection instances. Collection offset data can be found in

properties>object>collections [instance_offset]

Exact steps for others to reproduce the error

  1. put a cube in a collection and name the collection "myCollection"
  2. move the cube x = 10.
  3. change the collection offset to x = 10, y = 0, z = 10. Settings are found in properties>object>collections
  4. Create a collection instance of "myCollection"
  5. Move the collection instance to x = 20

the above steps can be found in attached .blend

  1. Export alembic
  2. Import alembic into a new scene.
  3. The imported alembic data has the wrong position OF THE CUBE that is a child to the collection instance locator.

Details

Type
Bug

Event Timeline

I found a little alembic bug today :-)

Extra clarification in the image. Added collection offset UI screendump

@Daniel Bystedt (dbystedt) nice find! Do you want & are you able to check how the USD exporter (in the experimental sybren-usd branch) handles this? If that handles it properly, it's even more motivation to get the USD exporter into the master branch, and rewrite the Alembic exporter to follow the same logic.

Philipp Oeser (lichtwerk) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.Nov 7 2019, 1:30 PM

I would love to try the sybren-usd branch.

It seems like the version on graphicall is old (2019-07-31) and there's no sybren-usd branch on https://builder.blender.org/download/branches/.

I have just been able to set up a build of blender on windows (visual studio, git, cmake etc) , but I need info regarding how to build or download sybren-usd branch

Congrats on the build setup :D It's going to be useful I'm sure.

For this test the version on graphicall is fine, because I haven't changed the USD implementation since.

I don't have any experience with building USD on Windows. @LazyDodo (LazyDodo) do you have time to write some instructions here? Then I can take those and turn them into a proper wiki page. We'll have to have those instructions at some point anyway ;-)

@Daniel Bystedt (dbystedt) I did the test with USD, and it is working properly there, so that's more motivation to get the Alembic exporter to use the same approach.

@Sybren A. Stüvel (sybren) Excellent! I also used the USD branch from craphicall.org and export usdc & usda without issues. However it seems that USD is missing in fiile>import (see attached image)

Yeah, it is indeed. There is no USD importer just yet, only an exporter.