USD Export Crash When Parent is disabled for rendering. #85729

New Issue

Jeroen Bakker · 2021-02-17T09:43:49+01:00

Jeroen Bakker commented

2021-02-17 09:43:49 +01:00

System Information
Operating system: Linux-5.4.0-65-generic-x86_64-with-glibc2.31 64 Bits
Graphics card: AMD Radeon RX 5700 (NAVI10, DRM 3.35.0, 5.4.0-65-generic, LLVM 11.0.0) X.Org 4.6 (Core Profile) Mesa 20.2.6

Blender Version
Broken:

version: 2.93.0 Alpha, branch: master, commit date: 2021-02-17 06:07, hash: 17dddc9417
2.83.12

Worked: (newest version of Blender that worked as expected)

Short description of error
When exporting render and an object parent is disabled for rendering there it crashes during USD export.
usdtest.blend

Exact steps for others to reproduce the error

Add a cube
Add an empty
Disable empty for render
Set cube parent to empty
Export USD file (Make sure that 'Render' is selected for 'Use Settings for'

NOTE: Use Settings for Viewport will work, Alembic export works.

The source of the crash is in AbstractHierarchyIterator::connect_loose_objects:

      /* 'object->parent' will never be nullptr here, as the export graph contains the
       * root as nullptr and thus will cause a break above. */
      BLI_assert(object->parent != nullptr);

      object = object->parent;

**System Information** Operating system: Linux-5.4.0-65-generic-x86_64-with-glibc2.31 64 Bits Graphics card: AMD Radeon RX 5700 (NAVI10, DRM 3.35.0, 5.4.0-65-generic, LLVM 11.0.0) X.Org 4.6 (Core Profile) Mesa 20.2.6 **Blender Version** Broken: * version: 2.93.0 Alpha, branch: master, commit date: 2021-02-17 06:07, hash: `17dddc9417` * 2.83.12 Worked: (newest version of Blender that worked as expected) **Short description of error** When exporting render and an object parent is disabled for rendering there it crashes during USD export. [usdtest.blend](https://archive.blender.org/developer/F9811621/usdtest.blend) **Exact steps for others to reproduce the error** * Add a cube * Add an empty * Disable empty for render * Set cube parent to empty * Export USD file (Make sure that 'Render' is selected for 'Use Settings for' NOTE: Use Settings for Viewport will work, Alembic export works. The source of the crash is in `AbstractHierarchyIterator::connect_loose_objects`: ``` /* 'object->parent' will never be nullptr here, as the export graph contains the * root as nullptr and thus will cause a break above. */ BLI_assert(object->parent != nullptr); object = object->parent; ```

Jeroen Bakker commented

2021-02-17 09:43:49 +01:00

Added subscriber: @Jeroen-Bakker

Jeroen Bakker changed title from ~~USD Export Crash When Parent is hidden disabled for rendering.~~ to USD Export Crash When Parent is disabled for rendering.

2021-02-17 09:46:14 +01:00

Philipp Oeser commented

2021-02-17 14:14:46 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Sonny Campbell commented

2022-06-08 12:02:46 +02:00

Added subscriber: @SonnyCampbell_Unity

Sonny Campbell commented

2022-06-08 12:02:46 +02:00

I've tested this and it happens for both USD and Alembic.

By default, USD exports with the "Visible Only" flag ticked.

By default, Alembic exports with the "Visible Only" flag unticked.

If you set "Use Settings For" to Render and "Visible Only" is ticked, it crashes both when exporting for USD and Alembic.

I've tested this and it happens for both USD and Alembic. By default, USD exports with the "Visible Only" flag ticked. ![UsdExport.png](https://archive.blender.org/developer/F13138151/UsdExport.png) By default, Alembic exports with the "Visible Only" flag unticked. ![AlembicExport.png](https://archive.blender.org/developer/F13138153/AlembicExport.png) If you set "Use Settings For" to Render and "Visible Only" is ticked, it crashes both when exporting for USD and Alembic.

Sonny Campbell self-assigned this 2022-06-13 12:28:53 +02:00

Sonny Campbell commented

2022-06-13 15:54:22 +02:00

This revision should fix the underlying crash raised in this bug. However I have a question about what the intended outcome is when exporting usd/alembic files.

If I set "Visible Only" and "Use Settings For" to Render, my assumption is that I should only export objects that are visible in a Render. If I disable a parent object for Render, and export the scene as in my screenshot here, should the Empty object be exported in my usd file? Currently it is being exported.

This revision should fix the underlying crash raised in this bug. However I have a question about what the intended outcome is when exporting usd/alembic files. If I set "Visible Only" and "Use Settings For" to Render, my assumption is that I should only export objects that are visible in a Render. If I disable a parent object for Render, and export the scene as in my screenshot here, should the Empty object be exported in my usd file? Currently it is being exported. ![image.png](https://archive.blender.org/developer/F13156441/image.png) ![image.png](https://archive.blender.org/developer/F13156443/image.png)

Sybren A. Stüvel commented

2022-06-13 16:15:22 +02:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2022-06-13 16:15:23 +02:00

Nice find!

In #85729#1373702, @SonnyCampbell_Unity wrote:
If I set "Visible Only" and "Use Settings For" to Render, my assumption is that I should only export objects that are visible in a Render. If I disable a parent object for Render, and export the scene as in my screenshot here, should the Empty object be exported in my usd file? Currently it is being exported.

Check the documentation for HierarchyIterator::weak_export:

/* When weak_export=true, the object will be exported only as transform, and only if is an

   * ancestor of an object with weak_export=false.
   *
   * In other words: when weak_export=true but this object has no children, or all descendants also
   * have weak_export=true, this object (and by recursive reasoning all its descendants) will be
   * excluded from the export.
   *
   * The export hierarchy is kept as close to the hierarchy in Blender as possible. As such, an
   * object that serves as a parent for another object, but which should NOT be exported itself, is
   * exported only as transform (i.e. as empty). This happens with objects that are part of a
   * holdout collection (which prevents them from being exported) but also parent of an exported
   * object. */

bool weak_export;

This means that the disabled parent will still be exported, but only as an Empty. Thus, testing this flow with Empties will hide some of the subtleties in the exporter.

Also I now see that the comment should be updated, the special handling of "holdout" collections was removed.

Nice find! > In #85729#1373702, @SonnyCampbell_Unity wrote: > If I set "Visible Only" and "Use Settings For" to Render, my assumption is that I should only export objects that are visible in a Render. If I disable a parent object for Render, and export the scene as in my screenshot here, should the Empty object be exported in my usd file? Currently it is being exported. Check the documentation for `HierarchyIterator::weak_export`: ```lang=c++ ``` /* When weak_export=true, the object will be exported only as transform, and only if is an ``` * ancestor of an object with weak_export=false. * * In other words: when weak_export=true but this object has no children, or all descendants also * have weak_export=true, this object (and by recursive reasoning all its descendants) will be * excluded from the export. * * The export hierarchy is kept as close to the hierarchy in Blender as possible. As such, an * object that serves as a parent for another object, but which should NOT be exported itself, is * exported only as transform (i.e. as empty). This happens with objects that are part of a * holdout collection (which prevents them from being exported) but also parent of an exported * object. */ ``` bool weak_export; ``` ``` This means that the disabled parent will still be exported, but only as an Empty. Thus, testing this flow with Empties will hide some of the subtleties in the exporter. Also I now see that the comment should be updated, the special handling of "holdout" collections was removed.

Sonny Campbell commented

2022-06-13 16:32:31 +02:00

Ok perfect, I missed that comment. That makes a lot of sense then, I also tested this with the usd_hierarchy_export_test.blend from the unit tests which has a more complex hierarchy of enabled/disabled objects, and that was where I first noticed it.

But yeah if that is expected then this should patch solve the crash. If you'd like I could update that comment to remove the line about the holdout collection too?

Ok perfect, I missed that comment. That makes a lot of sense then, I also tested this with the usd_hierarchy_export_test.blend from the unit tests which has a more complex hierarchy of enabled/disabled objects, and that was where I first noticed it. But yeah if that is expected then this should patch solve the crash. If you'd like I could update that comment to remove the line about the holdout collection too?

Sybren A. Stüvel commented

2022-06-14 12:16:27 +02:00

If you'd like I could update that comment to remove the line about the holdout collection too?

Thanks for the offer, but I've already done that ;-)

> If you'd like I could update that comment to remove the line about the holdout collection too? Thanks for the offer, but I've already done that ;-)

blender-admin commented

2022-06-14 12:16:40 +02:00

This issue was referenced by d209629806

This issue was referenced by d209629806aa8c3cd688082027ac5e8f6fefc206

Sybren A. Stüvel commented

2022-06-14 12:32:29 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Sybren A. Stüvel closed this issue

2022-06-14 12:32:29 +02:00

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USD Export Crash When Parent is disabled for rendering. #85729