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Joining with an object scaled to zero on one axis will make geometry disappear
Closed, ResolvedPublicKNOWN ISSUE

Description

System Information
Operating system: platform: Linux, Debian 9 AMD 64
Graphics card: VGA compatible controller: NVIDIA Corporation GK106 [GeForce GTX 650 Ti] (rev a1)

Blender Version
version: 2.83.5, branch: master, commit date: 2020-08-19 06:07, hash: c2b144df395f, type: Release
build date: 2020-08-19, 06:05:02

Short description of error
Join dose not work correctly in some case,

Exact steps for others to reproduce the error
There is a empty "plain box" around the Objects to Join, and shows up the join bug.

( Using shift select ) Select the Cube first then s001-#def-active-grp_curve_.007 and, (in object mode of course) Press Control J, and the Cube Disappears!
Change order of selection and Cube dose not disappear IE:
Select the s001-#def-active-grp_curve_.007 then the Cube and, (in object mode of course) Press Control J, and it works!

Attach files, and system info file from blender

Lachlan

Event Timeline

Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Confirmed.Mon, Aug 24, 2:31 PM
Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Known Issue".

Can confirm, not sure this is a bug though.

First of all, I think we are talking about objects Cube and s001-#def-active-grp_curve_.007 here? (report was misleading in saying Cube and Vert.001 -- this combination doesnt really have that problem)
The s001-#def-active-grp_curve_.007 object has a Z-scale of zero, which is taken into account after joining for the joined object.
If you select the other way around, the Cube Z-scale of 1 is taken into account after joining for the joined object - and this works well.

So the object doesnt really disappear, it is just not showing with a Z-scale of zero ;) -- I know this sounds weird.
It is not entirely clear to me if this happens in drawing code, but at least 2.79 behaved the same. (so it might as well be in actual modeling code...), it cannot be reproduced with scaling Z to zero after joining.

So as a workaround, just apply scale on s001-#def-active-grp_curve_.007 first, then joining should work no matter in which order selection happened.

Will keep as Known Issue for now.

Philipp Oeser (lichtwerk) renamed this task from Join dose not work correctly in some case. to Joining with an object scaled to zero on one axis will make geometry disappear.Mon, Aug 24, 2:33 PM
Philipp Oeser (lichtwerk) updated the task description. (Show Details)

Thanks Philipp,

I'm no Blender expert, I'm just learning fact. So was very confusing for the old 63 year brain LOL. Thanks for the good work around. And for you quick help!

lachlan

@Philipp Oeser (lichtwerk) agree this borderline bug/limitation, however I checked on supporting it and found it's possible to prevent the single degenerate axis from interfering with transforming object data on other axes.

@Lachlan Audas (lachlanA) be assured these kinds of issues impact users of all ages :) There is now a fix in master that handles the situation more gracefully, although we can't prevent the zero-scale from flattening the objects that are joined, so a warning is shown as well.