Maniphest T81037

Metaballs only work in the first scene
Closed, Archived

Assigned To
Germano Cavalcante (mano-wii)
Authored By
Gilberto Rodrigues (gilberto_rodrigues)
Sep 21 2020, 10:41 PM
Tags
  • BF Blender
Subscribers
Firepal64
Germano Cavalcante (mano-wii)
Gilberto Rodrigues (gilberto_rodrigues)
Yevgeny Makarov (jenkm)

Description

Blender Version
Broken: 2.79 to 2.90

Short description of error
Metaballs only work in the first scene. Except for linked scenes.

Exact steps for others to reproduce the error
Open default startup
Delete the cube
Add a metaball
New scene>full copy
The metaball will be invisible in the new scene and visible in the first.

Other way to reproduce the bug:

New file
delete cube
add metaball
New scene>new
add other metaball

Related Objects

Event Timeline

Gilberto Rodrigues (gilberto_rodrigues) created this task.Sep 21 2020, 10:41 PM
Firepal64 added a subscriber: Firepal64.Sep 22 2020, 8:58 AM

Can reproduce.

TL;DR Metaballs have a fundamental issue you can work around by creating a collection that contains a Metaball object with everything in it removed using Edit Mode.
You can link this collection to several scenes, and metaballs will work across them. Pretty hacky, but it does the job.


Here's my best assumption of what's happening:
The first metaball you add to any scene becomes the "metaball space origin" where Metaball geometry is generated.
Transforming this first metaball (moving it, rotating it, scaling it) changes the way geometry is generated for EVERY metaball object.
In fact, that first metaball IS where the scene's entire metaball geometry is generated. (Notice how selecting the geometry selects the first metaball!)

This is a problem, because Blender supports multiple scene where a metaball can be added.
Since the first metaball stores the geometry of all combined metaballs, if it is missing in one scene, you won't see any metaball geometry in that scene where it's missing.
(Which is exactly what this bug report is about.)

I propose that there be one "metaball space" per scene where geometry is generated. The metaball resolution settings would be in the Scene Properties menu.

Yevgeny Makarov (jenkm) added a subscriber: Yevgeny Makarov (jenkm).Sep 22 2020, 4:34 PM

https://docs.blender.org/manual/en/dev/modeling/metas/editing.html#meta-ball-object-families

When working with multiple scenes, take care naming your meta objects so the base is always in the same scene as other metas.
Failing to do so will give confusing behaviors (like invisible meta objects).

Gilberto Rodrigues (gilberto_rodrigues) added a comment.EditedSep 22 2020, 9:44 PM

@Yevgeny Makarov (jenkm) If there are naming restrictions, shouldn't blender itself name them properly when a scene is duplicated?

Germano Cavalcante (mano-wii) closed this task as Archived.Sep 24 2020, 11:14 PM
Germano Cavalcante (mano-wii) claimed this task.
Germano Cavalcante (mano-wii) added a subscriber: Germano Cavalcante (mano-wii).

These name "problems" are known.
It has even been discussed to rethink the metaballs solution (see T68890).

Thanks for the report, but there is no bug here, just a bad design.