Alembic integration improvements #69058

New Issue

Design task to coordinate the Alembic project.

Order of importance:

{icon circle color=red} Very Important - These we should handle before the next release.
{icon circle color=yellow} Somewhat Important - These issues would be nice to do as soon as possible
{icon circle color=green} Less Important - Extra polish, nice to have
? Incomplete - Tasks needing more details before implementing.

Open Bugs

{icon circle color=yellow} #54734 (Alembic Import does not respect remap relative)
{icon circle color=yellow} #55403 (Alembic: export of animated child hairs)
{icon circle color=yellow} #58704 (Animated alembic curves dont update on render) Probably requires #69046

Improvements

{icon circle color=yellow} #49114 (Exporting curves to Alembic crashes other software when reading)
{icon circle color=green} #51321 (AlembicObjectPath has a fixed-size char[])
{icon circle color=green} #73200 (Alembic: show animdata on CacheFile as sub-animdata of objects)

New Features

These features are related, in the sense that implementation would be possible (or at least easier) when #69046 is finished:

{icon circle color=yellow} #54050 (Alembic: Camera properties (focal length, focus distance, ...) animation not importing)
{icon circle color=yellow} #50725 (Alembic export doesn't take 'Custom Properties', as alembic non-standard data.)
{icon circle color=green} #49234 (Alembic not importing motion blur)
{icon circle color=green} #51311 (Support Alembic export/import of curve objects)

Other new features:

{icon circle color=green} #52646 (Alembic Instances are Duplicates instead of References)
{icon circle color=green} #51488 (Alembic export animated vertex color exports only first frame vertex color)

Design Tasks

{icon circle color=yellow} #54690 (Alembic design notes)
{icon circle color=green} #37578 (Point Cache replacement based on Alembic)

Design task to coordinate the Alembic project. Order of importance: - {icon circle color=red} **Very Important** - *These we should handle before the next release.* - {icon circle color=yellow} **Somewhat Important** - *These issues would be nice to do as soon as possible* - {icon circle color=green} **Less Important** - *Extra polish, nice to have* - `?` **Incomplete** - *Tasks needing more details before implementing.* # Open Bugs - {icon circle color=yellow} #54734 (Alembic Import does not respect remap relative) - {icon circle color=yellow} #55403 (Alembic: export of animated child hairs) - {icon circle color=yellow} #58704 (Animated alembic curves dont update on render) *Probably requires #69046* # Improvements - {icon circle color=yellow} #49114 (Exporting curves to Alembic crashes other software when reading) - {icon circle color=green} #51321 (AlembicObjectPath has a fixed-size char[]) - {icon circle color=green} #73200 (Alembic: show animdata on CacheFile as sub-animdata of objects) # New Features These features are related, in the sense that implementation would be possible (or at least easier) when #69046 is finished: - {icon circle color=yellow} #54050 (Alembic: Camera properties (focal length, focus distance, ...) animation not importing) - {icon circle color=yellow} #50725 (Alembic export doesn't take 'Custom Properties', as alembic non-standard data.) - {icon circle color=green} #49234 (Alembic not importing motion blur) - {icon circle color=green} #51311 (Support Alembic export/import of curve objects) Other new features: - {icon circle color=green} #52646 (Alembic Instances are Duplicates instead of References) - {icon circle color=green} #51488 (Alembic export animated vertex color exports only first frame vertex color) # Design Tasks - {icon circle color=yellow} #54690 (Alembic design notes) - {icon circle color=green} #37578 (Point Cache replacement based on Alembic)

Added subscriber: @dr.sybren

Added subscriber: @SteffenD

Added subscriber: @p2or

Hi Sybren,

I'm using alembic every day so many thanks for all your work and effort.

What I've noticed is that collections are ignored while exporting (flattened out). I think including/supporting collections might be a nice (and probably quick) improvement in order to keep the same hierarchy in other packages. I'm currently using a custom export operator, converting all the collections to empties before exporting the scene to alembic, which essentially is faking a group but is in fact just a quick and dirty workaround. Exporting heavy scenes just takes a few seconds longer so there is no real issue by that. However, in case there is any chance supporting groups/collections by default, would be a nice of course. In case you support that idea and you think I can help on that, providing or testing some files, just let me know. What do you think?

Thanks & Cheers,
Christian

Hi Sybren, I'm using alembic every day so many thanks for all your work and effort. What I've noticed is that *collections* are ignored while exporting (flattened out). I think including/supporting collections might be a nice (and probably quick) improvement in order to keep the same hierarchy in other packages. I'm currently using a custom export operator, converting all the collections to *empties* before exporting the scene to alembic, which essentially is *faking a group* but is in fact just a quick and dirty workaround. Exporting heavy scenes just takes a few seconds longer so there is no real issue by that. However, in case there is any chance supporting *groups/collections* by default, would be a nice of course. In case you support that idea and you think I can help on that, providing or testing some files, just let me know. What do you think? Thanks & Cheers, Christian

We're thinking of ways of including collections into the exported hierarchies, both for USD and Alembic, but it's not an active task at the moment. It's unfortunately not a quick thing to do, because:

Objects can be in multiple collections at once, and with different visibility states.
Collections can be instanced into the scene multiple times.
Empties can instance random subsets from a collection.
The parent/child hierarchy of objects in the scene is separate from the collection hierarchy, and thus collection boundaries can cross parent/child boundaries.

Because of the above points, there is no clear one-to-one mapping that will always work. The USD exporter currently supports case 2. from the above list, and properly handles cases where an object in an instanced collection has a parent outside that collection. I think that it's best to first get the USD exporter into master, then alter the Alembic exporter to use the improvements I made for USD, and then we can improve the way we handle collections.

We're thinking of ways of including collections into the exported hierarchies, both for USD and Alembic, but it's not an active task at the moment. It's unfortunately not a quick thing to do, because: 1. Objects can be in multiple collections at once, and with different visibility states. 2. Collections can be instanced into the scene multiple times. 3. Empties can instance random subsets from a collection. 4. The parent/child hierarchy of objects in the scene is separate from the collection hierarchy, and thus collection boundaries can cross parent/child boundaries. Because of the above points, there is no clear one-to-one mapping that will always work. The USD exporter currently supports case 2. from the above list, and properly handles cases where an object in an instanced collection has a parent outside that collection. I think that it's best to first get the USD exporter into master, then alter the Alembic exporter to use the improvements I made for USD, and then we can improve the way we handle collections.

Hey Sybren,

many thanks for that explanation, makes sense. Just thought, that's an easy thing to do and would improve it drastically consistency wise...

Thanks again,
Christian

Hey Sybren, many thanks for that explanation, makes sense. Just thought, that's an easy thing to do and would improve it drastically consistency wise... Thanks again, Christian

Added subscriber: @Momotron

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Added subscriber: @juang3d

HI Sybren.

Great to see this task! :D

Please don't forget about velocities or motion blur for fluid meshes (or variable vertex count meshes), right now we cannot render motion blur for fluids baked on alembic format.

Cheers.

HI Sybren. Great to see this task! :D Please don't forget about velocities or motion blur for fluid meshes (or variable vertex count meshes), right now we cannot render motion blur for fluids baked on alembic format. Cheers.

That is actually already in the tracker... #49234 (Alembic not importing motion blur)

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@ajohnson223 Please don't comment here to report issues or discuss problems; if you have found a bug, please file a bug report. I have removed your comment to keep the tracker clean; in case you don't agree, let me know in a private message.

@ajohnson223 Please don't comment here to report issues or discuss problems; if you have found a bug, please [file a bug report](https://www.youtube.com/watch?v=JTD0OJq_rF4). I have removed your comment to keep the tracker clean; in case you don't agree, let me know in a private message.

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Alembic integration improvements #69058

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