Parent behaviour: Parent to Object without Inverse needs an option to keep transform #95001

New Issue

Brad Clark · 2022-01-18T09:31:59+01:00

Brad Clark commented

2022-01-18 09:31:59 +01:00

Parenting behavior: Parent to Object without Inverse needs an option to keep transform
Current way it works

Parenting updates parent_inverse matrix if you keep offset. That helps to keep local transform identical before/after parenting, ensuring drivers, animation data, constraints etc. keep working as before.

Issues with the current methods:

Non-standard behavior, so people not familiar with Blender don’t expect this when working with hierarchies and parenting.
Parent_inverse matrix is hidden, so those same people won’t be able to easily figure out what’s going on.
It is inconsistent, as Unparent (Keep Transform) does seem to apply the visual transformation of the object transformation values, and seems to clear the inverse matrix. need to confirm

Conclusion of the discussion:

Add parenting option that doesn’t use parent-inverse but just updates child’s local transform values to keep it's visual transform. This is only truely possible when there is no inherited sheer, as the child's parent-inverse matrix can undo the sheer, but its loc/rot/scale properties cannot. Since this would be an additional option of the parenting menu, this is not a practical issue.
Add option to Apply Transform menu that applies the parent-inverse to the child’s local transform to remove hidden matrix values but visually the object stays in the same location, orientation and scale.

This will impact or change animation when used on animated objects but that is a limited use case that vs having a more user discoverable and understandable parenting operation where blender isn't "guessing" what the user wants to do and is hiding this from the user.

Referenced from https://devtalk.blender.org/t/2021-11-25-animation-rigging-module-meeting/21536#parenting-and-the-hidden-matrix-6

Parenting behavior: Parent to Object without Inverse needs an option to keep transform Current way it works Parenting updates parent_inverse matrix if you keep offset. That helps to keep local transform identical before/after parenting, ensuring drivers, animation data, constraints etc. keep working as before. Issues with the current methods: - Non-standard behavior, so people not familiar with Blender don’t expect this when working with hierarchies and parenting. - Parent_inverse matrix is hidden, so those same people won’t be able to easily figure out what’s going on. - It is inconsistent, as Unparent (Keep Transform) does seem to apply the visual transformation of the object transformation values, and seems to clear the inverse matrix. *need to confirm* Conclusion of the discussion: 1. Add parenting option that doesn’t use parent-inverse but just updates child’s local transform values to keep it's visual transform. This is only truely possible when there is no inherited sheer, as the child's parent-inverse matrix can undo the sheer, but its loc/rot/scale properties cannot. Since this would be an additional option of the parenting menu, this is not a practical issue. 2. Add option to Apply Transform menu that applies the parent-inverse to the child’s local transform to remove hidden matrix values but visually the object stays in the same location, orientation and scale. This will impact or change animation when used on animated objects but that is a limited use case that vs having a more user discoverable and understandable parenting operation where blender isn't "guessing" what the user wants to do and is hiding this from the user. Referenced from https://devtalk.blender.org/t/2021-11-25-animation-rigging-module-meeting/21536#parenting-and-the-hidden-matrix-6

Brad Clark commented

2022-01-18 09:31:59 +01:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Brad Clark commented

2022-01-18 09:31:59 +01:00

Added subscribers: @BClark, @zanqdo

Jason schleifer commented

2022-01-18 19:32:23 +01:00

Added subscriber: @JasonSchleifer

Orestis Konstantinidis commented

2022-01-19 12:01:08 +01:00

Added subscriber: @OrestisKonstantinidis

Ingo Clemens commented

2022-02-01 13:42:07 +01:00

Added subscriber: @iclemens

Sybren A. Stüvel commented

2022-02-08 10:38:40 +01:00

Added subscriber: @dr.sybren

Hadrien Brissaud commented

2022-02-08 17:51:41 +01:00

Added subscriber: @hadrien

Sybren A. Stüvel commented

2022-02-28 12:33:45 +01:00

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Muhammad Sohaib Arshid commented

2022-03-03 18:34:04 +01:00

Added subscriber: @Muhammad-Sohaib-Arshid

Muhammad Sohaib Arshid self-assigned this 2022-03-03 19:26:34 +01:00

Eigil commented

2022-03-04 16:41:37 +01:00

Added subscriber: @Eigil-Jarl-Halse

Andy Cuccaro commented

2022-03-05 05:04:25 +01:00

Added subscriber: @AndyCuccaro

Wayde Moss commented

2022-03-19 15:13:59 +01:00

Added subscriber: @wbmoss_dev

Wayde Moss commented

2022-03-19 15:13:59 +01:00

T95001_improved_parent_ops.py

Can some artists give this a try? @BClark

This is an addon that provides two operators: "#95001: Set Parent" and "#95001: Set Local Transform Origin". If its what you guys want, I can update the real operators.

#95001: Set Parent:
{F12934615}{F12934617}

The options (Preserve= World Transform, Origin= Parent) achieves (1). I don't know anything about sheer but it should work as long as the parent's world matrix is invertible.

#95001: Set Local Transform Origin
(No pictures because it has the same exact options as above. The only difference is that the parent isn't changed)

This is more about directly working with the child's local transform and what it's relative to. This operator achieves the control you're asking for (2).

I'm against exposing the inverse matrix. It doesn't seem useful. There are options for all the meaningful origins I could think of.
__
Misc:

I should've named "World Origin" to just "World"...
The old options aren't all exactly reproducible. I noticed that, for example, Set Parent (Without Inverse) will zero out the location but not the rotation, albeit a bit odd.

[T95001_improved_parent_ops.py](https://archive.blender.org/developer/F12934614/T95001_improved_parent_ops.py) Can some artists give this a try? @BClark This is an addon that provides two operators: "#95001: Set Parent" and "#95001: Set Local Transform Origin". If its what you guys want, I can update the real operators. **#95001: Set Parent:** {[F12934615](https://archive.blender.org/developer/F12934615/image.png)}{[F12934617](https://archive.blender.org/developer/F12934617/image.png)}![image.png](https://archive.blender.org/developer/F12934619/image.png) The options (Preserve= World Transform, Origin= Parent) achieves (1). I don't know anything about sheer but it should work as long as the parent's world matrix is invertible. **#95001: Set Local Transform Origin** (No pictures because it has the same exact options as above. The only difference is that the parent isn't changed) This is more about directly working with the child's local transform and what it's relative to. This operator achieves the control you're asking for (2). I'm against exposing the inverse matrix. It doesn't seem useful. There are options for all the meaningful origins I could think of. __ Misc: - I should've named "World Origin" to just "World"... - The old options aren't all exactly reproducible. I noticed that, for example, Set Parent (Without Inverse) will zero out the location but not the rotation, albeit a bit odd.

Brad Clark commented

2022-03-19 21:08:16 +01:00

Being able to see the inverse matrix allows for an understanding of what Blender is doing behind the scenes. It doesn't have to be visible along side the translate/rotate/scale but it should be able to be seen for troubleshooting without having to read/set/mess with it through scripting.

*Shearing is complicated to manage here because in Maya, there is another property just for that so when managing transforms with parent space stuff, it has special way to deal with it.

I will try and test this out today...thanks!

Being able to see the inverse matrix allows for an understanding of what Blender is doing behind the scenes. It doesn't have to be visible along side the translate/rotate/scale but it should be able to be seen for troubleshooting without having to read/set/mess with it through scripting. *Shearing is complicated to manage here because in Maya, there is another property just for that so when managing transforms with parent space stuff, it has special way to deal with it. I will try and test this out today...thanks!

Wayde Moss commented

2022-03-20 18:48:06 +01:00

It will be an update to original parent menu, replacing the 3 parenting options (Parent, Parent (Keep Transform), Parent (Without Inverse)) with the new two options.

Here are what's possible with the original 3 Set Parent variants.

	Preserve World Transform	Preserve Local Transform	Preserve only Local RotationScale	Zeroed out
Parent Origin			Set Parent (Without Inverse)	Clear Parent Inverse
World Origin	Set Parent (Keep Transform)	Set Parent ()	Set Parent(), then Alt+G	Set Parent(), then Alt+G/R/S
Child Origin
For the Child Origin row and missing Parent row elements, you can do it by copying/pasting transforms, temporarily moving the parent, etc. It's a hassle.

Here's what you get with the new options.

	Preserve World Transform	Preserve Local Transform	Preserve only Local RotationScale	Zeroed out
Parent Origin	(Origin=Parent, Preserve=World)	(Origin=Parent, Preserve= Local)	(Origin=Parent, Preserve= Local), then Alt+G to Clear local Location	(Origin=Parent, Preserve= ZeroOut)
World Origin	(Origin=World, Preserve= World)	(Origin=World, Preserve= Local)	(*)	(Origin=World, Preserve= ZeroOut)
Child Origin	.. and so on but with Origin=Child
(*) Not sure why you would, but its the same process as above w/ Origin=World

After reading a bit of the discussion, I changed my mind and do think its useful to expose the inverse matrix. It's effectively an offset from the parent. However, I won't be the one to add support for exposing the inverse matrix as I don't have sufficient math background for it. Workarounds for similar behavior can probably be done by just inserting an intermediate parent object and having the child's local transform origin be aligned with that intermediate parent object. No scripting needed.

It will be an update to original parent menu, replacing the 3 parenting options (Parent, Parent (Keep Transform), Parent (Without Inverse)) with the new two options. Here are what's possible with the original 3 Set Parent variants. | | Preserve World Transform | Preserve Local Transform | Preserve only Local RotationScale | Zeroed out | -- | -- | -- | -- | -- | | Parent Origin | | | Set Parent (Without Inverse) | Clear Parent Inverse | World Origin | Set Parent (Keep Transform) | Set Parent () | Set Parent(), then Alt+G | Set Parent(), then Alt+G/R/S | Child Origin | For the Child Origin row and missing Parent row elements, you can do it by copying/pasting transforms, temporarily moving the parent, etc. It's a hassle. Here's what you get with the new options. | | Preserve World Transform | Preserve Local Transform | Preserve only Local RotationScale | Zeroed out | -- | -- | -- | -- | -- | | Parent Origin | (Origin=Parent, Preserve=World) | (Origin=Parent, Preserve= Local) | (Origin=Parent, Preserve= Local), then Alt+G to Clear local Location | (Origin=Parent, Preserve= ZeroOut) | World Origin | (Origin=World, Preserve= World) | (Origin=World, Preserve= Local) | (*)| (Origin=World, Preserve= ZeroOut) | Child Origin | .. and so on but with Origin=Child (*) Not sure why you would, but its the same process as above w/ Origin=World After reading a bit of the discussion, I changed my mind and do think its useful to expose the inverse matrix. It's effectively an offset from the parent. However, I won't be the one to add support for exposing the inverse matrix as I don't have sufficient math background for it. Workarounds for similar behavior can probably be done by just inserting an intermediate parent object and having the child's local transform origin be aligned with that intermediate parent object. No scripting needed.

blender-admin commented

2022-04-15 00:16:23 +02:00

This issue was referenced by db6287873c

This issue was referenced by db6287873cd2c79741439f4d141c4b2db517d73e

Wayde Moss commented

2022-04-15 02:37:02 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Wayde Moss closed this issue

2022-04-15 02:37:02 +02:00

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Parent behaviour: Parent to Object without Inverse needs an option to keep transform #95001