Alembic Export: Camera resolution parameters not included. (resx, resy) #116375

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opened 2023-12-20 13:21:03 +01:00 by Yonatan-Bary · 7 comments

Yonatan-Bary commented

2023-12-20 13:21:03 +01:00

System Information
MacOS 12.2.1

Blender Version
4.0.0

The Problem:
Blender's cameras don't have specific resolution configured to them, instead they use the scene's resolution.
This is a problem when exporting a camera using Alembic. Other software (like Houdini) expects the resolution parameters on the camera itself.

Possible solution:
Store the scene's resolution on each camera that is exported.
The needed parameters looks like this (found using abcecho):

CompoundProperty name=.userProperties;schema=
ScalarProperty name=resx;interpretation=;datatype=float32_t;arraysize=1;numsamps=1
ScalarProperty name=resy;interpretation=;datatype=float32_t;arraysize=1;numsamps=1

Two alembic files attached:
One without the resx,resy parameters, exported from Blender.
The other with, exported from Houdini.

Thanks for the awesome work anyways!

**System Information** MacOS 12.2.1 **Blender Version** 4.0.0 **The Problem:** Blender's cameras don't have specific resolution configured to them, instead they use the scene's resolution. This is a problem when exporting a camera using Alembic. Other software (like Houdini) expects the resolution parameters on the camera itself. **Possible solution:** Store the scene's resolution on each camera that is exported. The needed parameters looks like this (found using abcecho): `CompoundProperty name=.userProperties;schema=` ` ScalarProperty name=resx;interpretation=;datatype=float32_t;arraysize=1;numsamps=1` ` ScalarProperty name=resy;interpretation=;datatype=float32_t;arraysize=1;numsamps=1` **Two alembic files attached:** One without the resx,resy parameters, exported from Blender. The other with, exported from Houdini. Thanks for the awesome work anyways!

No Resolution Parameters (exported from Blender).abc

1.8 KiB

With Resolution Parameters (exported from Houdini).abc

1.9 KiB

Yonatan-Bary added the

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Philipp Oeser commented

2023-12-20 13:45:57 +01:00

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Can check on this

Can check on this

Philipp Oeser self-assigned this 2023-12-20 13:46:04 +01:00

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Philipp Oeser commented

2023-12-20 14:18:03 +01:00

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Ah, misread this (these are implemented as userProperties in Houdini -- maybe Maya, too?, dont think they are part of the concept of a camera in alembic or USD itself... see https://docs.alembic.io/python/abcg.html#alembic.AbcGeom.CameraSample)

So this then looks like it is questionable to support these?

@dr.sybren : do you recall if we support userProperties outside the spec just to be compatible with other software?

Ah, misread this (these are implemented as `userProperties` in Houdini -- maybe Maya, too?, dont think they are part of the concept of a camera in alembic or USD itself... see https://docs.alembic.io/python/abcg.html#alembic.AbcGeom.CameraSample) So this then looks like it is questionable to support these? @dr.sybren : do you recall if we support `userProperties` outside the spec just to be compatible with other software?

Philipp Oeser removed their assignment 2023-12-20 14:18:10 +01:00

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Yonatan-Bary commented

2023-12-20 14:45:30 +01:00

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I found these userProperties in the alembic from Blender:
CompoundProperty name=.userProperties;schema=
ScalarProperty name=stereoDistance;interpretation=;datatype=float32_t;arraysize=1;numsamps=1
ScalarProperty name=eyeSeparation;interpretation=;datatype=float32_t;arraysize=1;numsamps=1
Don't know if this helps

I found these userProperties in the alembic from Blender: `CompoundProperty name=.userProperties;schema=` ` ScalarProperty name=stereoDistance;interpretation=;datatype=float32_t;arraysize=1;numsamps=1` ` ScalarProperty name=eyeSeparation;interpretation=;datatype=float32_t;arraysize=1;numsamps=1` Don't know if this helps

Sybren A. Stüvel commented

2023-12-21 16:08:47 +01:00

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@dr.sybren : do you recall if we support userProperties outside the spec just to be compatible with other software?

Last time I worked on USD we didn't, but I haven't been involved with that for a while now. USD is a way more sensible standard than Alembic, though. Much of Alembic is only standardised at the lowest level, and how to store things is often left to whatever application writes the files. There we do have some compatibility stuff, if it's clear enough how to write them.

The problem with adding these kind of compatibility options for proprietary applications is that it's hard to impossible to test whether it's done properly (unless someone sponsors, and keeps sponsoring, developers with Houdini licenses). In this particular case I don't think it'll hurt much to just include some .userProperties on the camera, though.

Other software (like Houdini) expects ...

@Yonatan-Bary what other packages than Houdini expect this?

> @dr.sybren : do you recall if we support `userProperties` outside the spec just to be compatible with other software? Last time I worked on USD we didn't, but I haven't been involved with that for a while now. USD is a way more sensible standard than Alembic, though. Much of Alembic is only standardised at the lowest level, and how to store things is often left to whatever application writes the files. There we do have some compatibility stuff, if it's clear enough how to write them. The problem with adding these kind of compatibility options for proprietary applications is that it's hard to impossible to test whether it's done properly (unless someone sponsors, and keeps sponsoring, developers with Houdini licenses). In this particular case I don't think it'll hurt much to just include some `.userProperties` on the camera, though. > Other software (like Houdini) expects ... @Yonatan-Bary what other packages than Houdini expect this?

Philipp Oeser commented

2024-01-04 11:44:25 +01:00

Member

OK, so will look into it.

@Yonatan-Bary : would still be good to know if Maya, Houdini (possibly others?) are compatible in that sense, do they all expect (on import) and provide (on export) these values in the same way?

/cam1/cam1Camera/.userProperties:
ScalarProperty      float32_t      resx[1]
ScalarProperty      float32_t      resy[1]

OK, so will look into it. @Yonatan-Bary : would still be good to know if Maya, Houdini (possibly others?) are compatible in that sense, do they all expect (on import) and provide (on export) these values in the same way? ``` /cam1/cam1Camera/.userProperties: ScalarProperty float32_t resx[1] ScalarProperty float32_t resy[1] ```

Philipp Oeser added

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Philipp Oeser self-assigned this 2024-01-04 11:44:50 +01:00

Philipp Oeser referenced a pull request that will close this issue

2024-01-04 14:20:14 +01:00

Alembic: export render resolution on cameras #116782

Philipp Oeser commented

2024-01-04 14:23:54 +01:00

Member

@Yonatan-Bary : I made a PR implementing this, see !116782

There will also be be builds to test this (see link in the PR), testing this out would be highly appreciated, thx in advance!

@Yonatan-Bary : I made a PR implementing this, see !116782 There will also be be builds to test this (see link in the PR), testing this out would be highly appreciated, thx in advance!

Philipp Oeser referenced this issue from a commit

2024-01-04 17:49:41 +01:00

Alembic: export render resolution on cameras

Philipp Oeser closed this issue

2024-01-04 17:49:42 +01:00

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Philipp Oeser commented

2024-01-04 17:51:13 +01:00

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@Yonatan-Bary : committed 5412bd48a9

So you should be able to verify it works in tomorrows 4.1 build from https://builder.blender.org/download/daily/

@Yonatan-Bary : committed 5412bd48a9ef7395b0841906200c028f05994f03 So you should be able to verify it works in tomorrows 4.1 build from https://builder.blender.org/download/daily/

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