StretchTo constraint: Apply Pose as Rest Pose changes bone length #79553

New Issue

W.Volbers · 2020-08-05T15:34:56+02:00

W.Volbers commented

2020-08-05 15:34:56 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1060 3GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.77

Blender Version
Broken: version: 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: 353e5bd749
Worked: never
Short description of error
bonelength changing to wrong length when apply new Rest Pose

Exact steps for others to reproduce the error

add armature
subdivide bone in three bones,
select the top bone -clear bones
go to Pose mode
apply second bone a stretch-constraint to the last bone(tip)

rearrange the bones in Posemode to an new Pose
select with boxselect all bones
Apply Pose as Rest Pose (menu Pose, Ctrl A)
the green Bone with the stretch-constraint will have now a wrong bonelenght,

I'm not sure if this is a bug, but what seems strange to me is that the bone is displayed correctly in edit mode

workaround press reset inside the Add Bone Constraint

apply_new_Rest-Pose.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1060 3GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.77 **Blender Version** Broken: version: 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: `353e5bd749` Worked: never **Short description of error** bonelength changing to wrong length when apply new Rest Pose ![before.JPG](https://archive.blender.org/developer/F8748419/before.JPG) ![after.jpg](https://archive.blender.org/developer/F8748421/after.jpg) **Exact steps for others to reproduce the error** add armature subdivide bone in three bones, select the top bone -clear bones go to Pose mode apply second bone a stretch-constraint to the last bone(tip) rearrange the bones in Posemode to an new Pose select with boxselect all bones Apply Pose as Rest Pose (menu Pose, Ctrl A) the green Bone with the stretch-constraint will have now a wrong bonelenght, *I'm not sure if this is a bug, but what seems strange to me is that the bone is displayed correctly in edit mode* **workaround press reset inside the Add Bone Constraint** ![workaround.JPG](https://archive.blender.org/developer/F8748445/workaround.JPG) [apply_new_Rest-Pose.blend](https://archive.blender.org/developer/F8748426/apply_new_Rest-Pose.blend)

W.Volbers commented

2020-08-05 15:34:56 +02:00

Added subscriber: @walt-3

Richard Antalik commented

2020-08-06 04:33:13 +02:00

Added subscribers: @dr.sybren, @iss

Richard Antalik commented

2020-08-06 04:33:13 +02:00

Not sure if this is bug, strictly speaking. @dr.sybren Should applying rest pose recalculate this value?

Philipp Oeser commented

2020-08-27 18:23:04 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-08-27 18:23:04 +02:00

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

Philipp Oeser commented

2020-08-27 18:23:04 +02:00

I would think this is a bug (maybe it is a Known Limitation).
I think if you apply a new Rest Pose, one would expect also the mesh to not deform anymore.
With the current behavior, this is not the case, so you end up with a rest pose which already deforms.

I would think this is a bug (maybe it is a Known Limitation). I think if you apply a new Rest Pose, one would expect also the mesh to not deform anymore. With the current behavior, this is not the case, so you end up with a rest pose which already deforms.

Philipp Oeser changed title from ~~set new Rest Pose change the bonelenght~~ to Apply Pose as Rest Pose change the bonelenght (due to StretchTo constraints rest length not being reset)

2020-08-27 18:24:19 +02:00

Sybren A. Stüvel commented

2020-08-31 12:43:21 +02:00

Changed status from 'Confirmed' to: 'Needs User Info'

Sybren A. Stüvel commented

2020-08-31 12:43:21 +02:00

Please test this with a few older versions of Blender. Knowing whether a bug was recently introduced or has been in Blender for longer will help developers in finding the root cause of the issue.

Please test this with a few [older versions of Blender](https://download.blender.org/release/). Knowing whether a bug was recently introduced or has been in Blender for longer will help developers in finding the root cause of the issue.

W.Volbers commented

2020-08-31 13:27:20 +02:00

behaves the same way in v2.80.75,
the versions before that I leave out

behaves the same way in v2.80.75, the versions before that I leave out

Sybren A. Stüvel commented

2020-08-31 15:07:27 +02:00

Changed status from 'Needs User Info' to: 'Confirmed'

Sybren A. Stüvel commented

2020-08-31 15:07:27 +02:00

Thanks for testing this @walt.

I'm not sure if this is a bug, but what seems strange to me is that the bone is displayed correctly in edit mode

This isn't so strange. The current pose is simply copied to the rest pose, which is what you see in edit mode. The Stretch To constraint applies a scale factor on top of the rest pose, and this scale factor is still the same after the operator has finished. This is why the bone becomes too long -- effectively the scale factor from the constraint is shown twice.

The code for the "Apply as Rest Pose" operator doesn't have anything for updating affected constraints or modifiers. The problem here is that the Rest Length property could have been adjusted by an artist, or even animated, so Blender can't just reset it and assume then everything will be alright.

Thanks for testing this @walt. > I'm not sure if this is a bug, but what seems strange to me is that the bone is displayed correctly in edit mode This isn't so strange. The current pose is simply copied to the rest pose, which is what you see in edit mode. The Stretch To constraint applies a scale factor on top of the rest pose, and this scale factor is still the same after the operator has finished. This is why the bone becomes too long -- effectively the scale factor from the constraint is shown twice. The code for the "Apply as Rest Pose" operator doesn't have anything for updating affected constraints or modifiers. The problem here is that the Rest Length property could have been adjusted by an artist, or even animated, so Blender can't just reset it and assume then everything will be alright.

Sybren A. Stüvel commented

2020-08-31 15:57:43 +02:00

Having said that, applying as rest pose will break existing animation anyway, so I think we can reset the rest length of the constraint.

W.Volbers commented

2020-08-31 16:06:09 +02:00

yes exactly,
i would not use this anymore when i am done with rigging .

( just to avoid misunderstandings,
the "apply pose as rest pose" would mainly drop the rigging process.)

yes exactly, i would not use this anymore when i am done with rigging . ( just to avoid misunderstandings, the "apply pose as rest pose" would mainly drop the rigging process.)

Sybren A. Stüvel commented

2020-08-31 16:56:33 +02:00

I have no idea what "dropping the rigging process" means.

In my test build, I have the "automatic reset button" working. It still produces a visual change, though. Edit bones don't have scale, which means that the stretching & squashing of the constraint (to maintain volume) cannot be copied to the rest pose. As a result, a bone that's stretched thin will become full size again:

@walt-3 Would this be the expected behaviour?

I have no idea what "dropping the rigging process" means. In my test build, I have the "automatic reset button" working. It still produces a visual change, though. Edit bones don't have scale, which means that the stretching & squashing of the constraint (to maintain volume) cannot be copied to the rest pose. As a result, a bone that's stretched thin will become full size again: ![apply-as-rest-pose-#79553.png](https://archive.blender.org/developer/F8825842/apply-as-rest-pose-#79553.png) @walt-3 Would this be the expected behaviour?

Sybren A. Stüvel changed title from ~~Apply Pose as Rest Pose change the bonelenght (due to StretchTo constraints rest length not being reset)~~ to StretchTo constraint: Apply Pose as Rest Pose changes bone length

2020-08-31 17:18:07 +02:00

blender-admin commented

2020-09-01 17:57:42 +02:00

This issue was referenced by a92ab93c7d

This issue was referenced by a92ab93c7dc3f54ffd8290dd8055998a2c932998

Sybren A. Stüvel commented

2020-09-01 17:58:27 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Sybren A. Stüvel closed this issue

2020-09-01 17:58:27 +02:00

Sybren A. Stüvel self-assigned this 2020-09-01 17:58:27 +02:00

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

StretchTo constraint: Apply Pose as Rest Pose changes bone length #79553