Array modifier is crazy, when using "object offset" pointed to empty, which is parented to curve #76565

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opened 2020-05-08 21:33:32 +02:00 by Volodymyr · 9 comments

System Information
Operating system: Mac OS Catalina 10.15.4 (latest)
Graphics card: Intel HD 6000

Blender Version
Broken: 2.83 beta as of 8-th of May

Short description of error
Array modifier is crazy, when using "object offset" pointed to empty, which is parented to curve. And when the CURVE CONVERTED TO MESH -- it just destroys scale of object!

Exact steps for others to reproduce the error

  1. Open .blend
    plants.blend
  2. Try to move empty -- everything works fine
  3. Select "empty" and "petals" (with shift) then parent them (Ctrl + P -- to object) to "bezier curve"
  4. Select bezier curve and "convert to mesh"
  5. Now try to move empty

Before:
Screenshot 2020-05-08 at 22.32.55.png
After:
Screenshot 2020-05-08 at 22.33.14.png

**System Information** Operating system: Mac OS Catalina 10.15.4 (latest) Graphics card: Intel HD 6000 **Blender Version** Broken: 2.83 beta as of 8-th of May **Short description of error** Array modifier is crazy, when using "object offset" pointed to empty, which is parented to curve. And when the CURVE CONVERTED TO MESH -- it just destroys scale of object! **Exact steps for others to reproduce the error** 1) Open .blend [plants.blend](https://archive.blender.org/developer/F8521349/plants.blend) 2) Try to move empty -- everything works fine 3) Select "empty" and "petals" (with shift) then parent them (Ctrl + P -- to object) to "bezier curve" 4) Select bezier curve and "convert to mesh" 5) Now try to move empty Before: ![Screenshot 2020-05-08 at 22.32.55.png](https://archive.blender.org/developer/F8521358/Screenshot_2020-05-08_at_22.32.55.png) After: ![Screenshot 2020-05-08 at 22.33.14.png](https://archive.blender.org/developer/F8521360/Screenshot_2020-05-08_at_22.33.14.png)
Author

Added subscriber: @linosia

Added subscriber: @linosia
Member

Added subscriber: @Alaska

Added subscriber: @Alaska
Member

I have tested in Blender 2.82a, 2.83 ce76e17584 (2020-05-08 14:49) and 2.90 6f985574b7 (2020-05-08) and can confirm this occurs. The issue is caused by the scale of the empty changing when the curve is converted to a mesh. And because the array takes into account the scale of the empty, the array will enlarge.

I have tested in Blender 2.82a, 2.83 ce76e17584ee (2020-05-08 14:49) and 2.90 6f985574b775 (2020-05-08) and can confirm this occurs. The issue is caused by the scale of the empty changing when the curve is converted to a mesh. And because the array takes into account the scale of the empty, the array will enlarge.
Member

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

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

Added subscribers: @mont29, @Sergey

Added subscribers: @mont29, @Sergey

The root of the issue here is that for curves which have "Path Animation" enabled object parent works different: it will parent the object to a point on the curve path which corresponds to the path's "Evaluation Time" setting. Converting the curve to mesh makes parenting work different.

It is probably possible to avoid object from movement in some simple cases like this (by manipulating the inverse parent matrix), but don't think this is possible to solve in general. Not sure if it worth trying to keep children transform. @mont29 ?

One thing we should do is to fix missing update tag, something like this should do it: P1383. Something where Bastien might want to have second look at.

The root of the issue here is that for curves which have "Path Animation" enabled object parent works different: it will parent the object to a point on the curve path which corresponds to the path's "Evaluation Time" setting. Converting the curve to mesh makes parenting work different. It is probably possible to avoid object from movement in some simple cases like this (by manipulating the inverse parent matrix), but don't think this is possible to solve in general. Not sure if it worth trying to keep children transform. @mont29 ? One thing we should do is to fix missing update tag, something like this should do it: [P1383](https://archive.blender.org/developer/P1383.txt). Something where Bastien might want to have second look at.

@Sergey I would not spend time trying to 'fix' this indeed, would expect it to be hairy at best, and this is really a corner case, not a bug anyway. Change on update tag sounds good to me.

@Sergey I would not spend time trying to 'fix' this indeed, would expect it to be hairy at best, and this is really a corner case, not a bug anyway. Change on update tag sounds good to me.

Committed the ID tag, so all the updates are done as soon as possible.

The fact that parenting to curve and mesh work differently is a design decision. Attempts to try preserve children transform will be fragile, so considering this known behavior.

Thanks for the report!

Committed the ID tag, so all the updates are done as soon as possible. The fact that parenting to curve and mesh work differently is a design decision. Attempts to try preserve children transform will be fragile, so considering this known behavior. Thanks for the report!
Member

Removed subscriber: @Alaska

Removed subscriber: @Alaska
Philipp Oeser removed the
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Reference: blender/blender#76565
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