Alembic Exports Particles Wrong? #87351

New Issue

Atomic · 2021-04-09T19:15:13+02:00

Atomic commented

2021-04-09 19:15:13 +02:00

System Information
system-info.txt

Blender Version
Broken: 2.92

Short description of error
Alembic Exports Particles Wrong

Exact steps for others to reproduce the error
The image shows the problem. Green is the source that generates the white alembic. They should be the same.

It looks like all the particles are presented on frame #1, then simulated to fall as a clump, instead being born over time and falling one by one. Also, the export does not take into account the Show Emitter flag for the particle system. Most users won't want the emitter surface exported, and I can't find anyway to remove it using Blender.

1.) Download the file and export the simulation as an Alembic.
2.) Import result to observe the failure.

alembic_particle_failure.zip

**System Information** [system-info.txt](https://archive.blender.org/developer/F9926967/system-info.txt) **Blender Version** Broken: 2.92 **Short description of error** Alembic Exports Particles Wrong **Exact steps for others to reproduce the error** The image shows the problem. Green is the source that generates the white alembic. They should be the same. ![Untitled-1.jpg](https://archive.blender.org/developer/F9926970/Untitled-1.jpg) It looks like all the particles are presented on frame #1, then simulated to fall as a clump, instead being born over time and falling one by one. Also, the export does not take into account the *Show Emitter* flag for the particle system. Most users won't want the emitter surface exported, and I can't find anyway to remove it using Blender. ![blender_particles.gif](https://archive.blender.org/developer/F9926974/blender_particles.gif) 1.) Download the file and export the simulation as an Alembic. 2.) Import result to observe the failure. [alembic_particle_failure.zip](https://archive.blender.org/developer/F9926980/alembic_particle_failure.zip)

Atomic commented

2021-04-09 19:15:13 +02:00

Added subscriber: @AtomP

Atomic commented

2021-04-09 19:24:15 +02:00

Another thing to note, is that if you use the alembic in another program it is totally wrong. Here is the same Blender generated .abc file inside of Houdini.

Multiple failures. All particles are presented at once, and the timeline just stops after 72 frames, when I kicked out 250 from Blender?

Another thing to note, is that if you use the alembic in another program it is totally wrong. Here is the same Blender generated .abc file inside of Houdini. ![alembic_particles.gif](https://archive.blender.org/developer/F9926995/alembic_particles.gif) Multiple failures. All particles are presented at once, and the timeline just stops after 72 frames, when I kicked out 250 from Blender?

Philipp Oeser commented

2021-04-12 11:54:56 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-04-12 11:54:56 +02:00

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

Philipp Oeser commented

2021-04-12 11:54:56 +02:00

Can confrim, will check.

Steffen Dünner commented

2021-04-12 12:16:59 +02:00

Added subscriber: @SteffenD

Philipp Oeser self-assigned this 2021-04-12 14:16:30 +02:00

Philipp Oeser commented

2021-04-12 14:16:30 +02:00

Afaict, those duplis actually should not be exported at all.
Particle export should be animated points, thats it.

Will do one further check (but could very well be that this should just be removed again)

Afaict, those duplis actually should not be exported at all. Particle export should be animated points, thats it. Will do one further check (but could very well be that this should just be removed again)

Atomic commented

2021-04-12 15:44:51 +02:00

If the system is set to render as object, yes, those duplis should be exported. If the system is set to Halo, then only points.

Philipp Oeser commented

2021-04-12 16:12:56 +02:00

In #87351#1145249, @AtomP wrote:
If the system is set to render as object, yes, those duplis should be exported. If the system is set to Halo, then only points.

Dont think so:
https://docs.blender.org/manual/en/dev/files/import_export/alembic.html#particle-systems

These were not exported in b21ba5e579 (Jun28), but then in baf124c753 (Jul05) they were - which I assume only happened by accident?
[having trouble bisecting this due to seemingly unrelated build errors]

> In #87351#1145249, @AtomP wrote: > If the system is set to render as object, yes, those duplis should be exported. If the system is set to Halo, then only points. Dont think so: https://docs.blender.org/manual/en/dev/files/import_export/alembic.html#particle-systems These were not exported in b21ba5e579 (Jun28), but then in baf124c753 (Jul05) they were - which I assume only happened by accident? [having trouble bisecting this due to seemingly unrelated build errors]

Philipp Oeser removed their assignment 2021-04-12 16:15:21 +02:00

Philipp Oeser commented

2021-04-12 16:15:21 +02:00

Added subscriber: @dr.sybren

Philipp Oeser commented

2021-04-12 16:15:21 +02:00

That being said, we could add a check in should_visit_dupli_objectfor dupli_object->particle_system, but since the intentions are unclear, I would rather have @dr.sybren comment on this.

That being said, we could add a check in `should_visit_dupli_object`for `dupli_object->particle_system`, but since the intentions are unclear, I would rather have @dr.sybren comment on this.

Alessandro Mastronardi commented

2021-11-21 01:11:47 +01:00

Added subscriber: @papillon68

Alessandro Mastronardi commented

2021-11-21 01:11:47 +01:00

Any update on this?

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Alembic Exports Particles Wrong? #87351