Armature modifier "Preserve Volume" breaks when scaling #100373

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Mark · 2022-08-12T15:48:25+02:00

Mark commented

2022-08-12 15:48:25 +02:00

Memory: 16 GB RAM
Processor: AMD Ryzen 5 3600 6-Core Processor 3.59 GHz
Operating System: Windows 10
Graphics card: NVIDIA 2060 RTX (8GB VRAM)

SCENE DESCRIPTION

Blender Version 3.2.1
Broken: 3.2.1, preserve_volume_broken.blend, 2022-08-12
Broken: 3.2.1 AND 3.0.1, rain_v2.1.blend, 2020-09-22

preserve_volume_broken.blend

NOTE: This bug is also apparent in the official Rain_v2.1.blend file downloaded from studio.blender.org. Curiously, this rig has preserve volume checked off by default. The only changes was the Corrective Smooth modifier toggled off in both the viewport and render views and posed with the root bone scaled to 0.1.

BUG DESCRIPTION:

Scaling down bones will break deformations on mesh objects which have "Preserve Volume" checked on in the Armature modifier.
Scaling the Armature object itself however will not break the deformations while Preserve Volume is on.
I believe perhaps "Preserve Volume" operates only at Object level only and not at Armature level.

Without preserve volume:

With preserve volume:

From the simplified file provided
Preserve volume before scaling:

Preserve volume after scaling:

HOW TO REPRODUCE THE ERROR:

Open the preserve_volume_broken.blend file
Scale down the "root - SCALE THIS BONE" bone in pose mode.
Move the other tweak bones so see how the deformation breaks while "Preserve Volume" is checked on in the Cylinder's armature modifier.
Check off the "Preserve Volume" option in the Armature modifier so see the difference.

NOTE: The file provided I feel perfectly illustrates a) the need for preserve volume and b) how the preserve volume uses the armature object scale and not the parent bone's scale at armature level. I have not seen a blender version where this performs as expected.

Memory: 16 GB RAM Processor: AMD Ryzen 5 3600 6-Core Processor 3.59 GHz Operating System: Windows 10 Graphics card: NVIDIA 2060 RTX (8GB VRAM) `SCENE DESCRIPTION` **Blender Version 3.2.1** Broken: 3.2.1, preserve_volume_broken.blend, 2022-08-12 Broken: 3.2.1 AND 3.0.1, rain_v2.1.blend, 2020-09-22 [preserve_volume_broken.blend](https://archive.blender.org/developer/F13387219/preserve_volume_broken.blend) NOTE: This bug is also apparent in the official Rain_v2.1.blend file downloaded from studio.blender.org. Curiously, this rig has preserve volume checked off by default. The only changes was the Corrective Smooth modifier toggled off in both the viewport and render views and posed with the root bone scaled to 0.1. `BUG DESCRIPTION`: Scaling down bones will break deformations on mesh objects which have "Preserve Volume" checked on in the Armature modifier. Scaling the Armature object itself however will not break the deformations while Preserve Volume is on. I believe perhaps "Preserve Volume" operates only at Object level only and not at Armature level. Without preserve volume: ![without preserve volume.PNG](https://archive.blender.org/developer/F13371007/without_preserve_volume.PNG) With preserve volume: ![with preserve volume.PNG](https://archive.blender.org/developer/F13371010/with_preserve_volume.PNG) **From the simplified file provided** Preserve volume before scaling: ![preserve_volume_before_scaling.PNG](https://archive.blender.org/developer/F13371039/preserve_volume_before_scaling.PNG) Preserve volume after scaling: ![preserve_volume_after_scaling.PNG](https://archive.blender.org/developer/F13371058/preserve_volume_after_scaling.PNG) `HOW TO REPRODUCE THE ERROR`: 1) Open the preserve_volume_broken.blend file 2) Scale down the ***"root - SCALE THIS BONE"*** bone in pose mode. 3) Move the other tweak bones so see how the deformation breaks while "Preserve Volume" is checked on in the Cylinder's armature modifier. 4) Check off the "Preserve Volume" option in the Armature modifier so see the difference. NOTE: The file provided I feel perfectly illustrates a) the need for preserve volume and b) how the preserve volume uses the armature object scale and not the parent bone's scale at armature level. I have not seen a blender version where this performs as expected.

Mark commented

2022-08-12 15:48:25 +02:00

Added subscriber: @Munkle_Mark

Omar Emara commented

2022-08-15 13:08:14 +02:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-08-15 13:08:14 +02:00

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

Omar Emara commented

2022-08-15 13:08:14 +02:00

It seems you forgot to upload the file, can you do that? Did this used to work in any older version that you know of?

Omar Emara commented

2022-08-15 14:21:30 +02:00

Closed as duplicate of #43188

Omar Emara closed this issue

2022-08-15 14:21:30 +02:00

Mark commented

2022-08-15 14:41:09 +02:00

In #100373#1403840, @OmarEmaraDev wrote:
It seems you forgot to upload the file, can you do that? Did this used to work in any older version that you know of?

Ah yes, I did forget. I've edited the original task to include the blend file. Sorry about that.

I've tested this as far back as 2.79b and also in 2.83 (the earliest of the 2.8x series I have on my system) and the problem persists there.

preserve_volume_broken_2-83.blend

preserve_volume_broken_2-79b.blend

> In #100373#1403840, @OmarEmaraDev wrote: > It seems you forgot to upload the file, can you do that? Did this used to work in any older version that you know of? Ah yes, I did forget. I've edited the original task to include the blend file. Sorry about that. I've tested this as far back as 2.79b and also in 2.83 (the earliest of the 2.8x series I have on my system) and the problem persists there. [preserve_volume_broken_2-83.blend](https://archive.blender.org/developer/F13387360/preserve_volume_broken_2-83.blend) [preserve_volume_broken_2-79b.blend](https://archive.blender.org/developer/F13387359/preserve_volume_broken_2-79b.blend)

Omar Emara commented

2022-08-15 14:50:16 +02:00

Thanks. As you can see in the report to which this was merged, this is considered a known limitation. But it is marked as a TODO and listed in #55365, so maybe it will be fixed in the future, though it is unlikely to happen soon.

Mark commented

2022-08-15 15:04:32 +02:00

Thanks for the clarification.

I had been looking for a duplicate and saw this page but the description was a bit vague and perhaps that's why I overlooked it when searching with keywords but the task #43188 is indeed the same issue.

Thanks for the clarification. I had been looking for a duplicate and saw this page but the description was a bit vague and perhaps that's why I overlooked it when searching with keywords but the task [#43188 ](https://developer.blender.org/T43188) is indeed the same issue.

himisa referenced this issue

2023-05-22 08:42:58 +02:00

Fix #32022, #43188, #100373, Armature modifier - Preserve volume + Scale #108134

Nathan Vegdahl referenced this issue from a commit

2023-06-06 12:32:01 +02:00

Fix #32022, #43188, #100373, Armature modifier - Preserve volume + Scale

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