Maintain Volume constraint appears to have no effect in 2.79 #57793

New Issue

Aaron Powell · 2018-11-12T17:07:36+01:00

Aaron Powell commented

2018-11-12 17:07:36 +01:00

System Information
Fedora 28, dual NVIDIA 1080 GTX cards

Blender Version
Broken: 2.79b f4dc9f9d68
Worked: 2.78

The Maintain Volume constraint appears to have no effect when combined with an IK constraint. I created a stretchy leg rig for a character in Blender 2.78 following this tutorial (https://www.youtube.com/watch?v=m-ErKAsL4QE) a while ago, and when I upgraded to Blender 2.79 the rig no longer held its volume like it did in 2.78.

The constraint works on its own, but if it's combined with the stretch IK features it appears to have no effect anymore. I'm assuming it's a bug but it could have also been a change by design.

Exact steps for others to reproduce the error
Open attached blend file and move the foot controller around. No errors or warnings thrown in the console.

maintain_volume_example.blend

**System Information** Fedora 28, dual NVIDIA 1080 GTX cards **Blender Version** Broken: 2.79b f4dc9f9d68b Worked: 2.78 The Maintain Volume constraint appears to have no effect when combined with an IK constraint. I created a stretchy leg rig for a character in Blender 2.78 following this tutorial (https://www.youtube.com/watch?v=m-ErKAsL4QE) a while ago, and when I upgraded to Blender 2.79 the rig no longer held its volume like it did in 2.78. The constraint works on its own, but if it's combined with the stretch IK features it appears to have no effect anymore. I'm assuming it's a bug but it could have also been a change by design. **Exact steps for others to reproduce the error** Open attached blend file and move the foot controller around. No errors or warnings thrown in the console. [maintain_volume_example.blend](https://archive.blender.org/developer/F5515618/maintain_volume_example.blend)

Aaron Powell commented

2018-11-12 17:07:36 +01:00

Added subscriber: @lunadigital

Bastien Montagne commented

2018-11-29 16:33:54 +01:00

Added subscribers: @brecht, @mont29

Bastien Montagne commented

2018-11-29 16:33:54 +01:00

Am not sure it's working better in 2.78? Bone scale in XZ plane remains the same, while in 2.79 it increases, but this is not affected by MaintainVolume constraint afaikt.

@brecht, iirc you are pretty familiar with IK and such, maybe you know more here?

Am not sure it's working better in 2.78? Bone scale in XZ plane remains the same, while in 2.79 it increases, but this is not affected by MaintainVolume constraint afaikt. @brecht, iirc you are pretty familiar with IK and such, maybe you know more here?

Michael Soluyanov commented

2019-03-29 11:21:27 +01:00

Added subscriber: @crantisz

Michael Soluyanov commented

2019-03-29 11:21:27 +01:00

This not working at all in all versions from 2.5 to 2.80. In video there is a walkaround - additional bones copy loc rot scale, then afterwords - maintain volume.

Philipp Oeser commented

2019-03-29 11:44:19 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2019-03-29 11:44:19 +01:00

Just as a note: behavior changed in ec76f38b09 and again in a9509a2f8a (but apparently unrelated? -- like mentioned this also isnt working before these commits...)

Just as a note: behavior changed in ec76f38b09 and again in a9509a2f8a (but apparently unrelated? -- like mentioned this also isnt working before these commits...)

Alexander Gavrilov commented

2019-05-06 21:02:58 +02:00

Added subscriber: @angavrilov

Alexander Gavrilov commented

2019-05-06 21:02:58 +02:00

I just changed Maintain Volume yet again in 2.8 - now it has a dropdown to choose from all ways it has been working up to now.

Regarding IK, however, even without looking at the file this sounds like a misunderstanding of how IK works. Specifically, IK always runs after all constraints on its bones (irrespective of the ordering of the IK constraint itself in the stack), so to apply further constraints to its result, it is mandatory to make a new chain with Copy Transforms - that's not a 'workaround'.

I just changed Maintain Volume yet again in 2.8 - now it has a dropdown to choose from all ways it has been working up to now. Regarding IK, however, even without looking at the file this sounds like a misunderstanding of how IK works. Specifically, IK always runs after all constraints on its bones (irrespective of the ordering of the IK constraint itself in the stack), so to apply further constraints to its result, it is mandatory to make a new chain with Copy Transforms - that's not a 'workaround'.

Brecht Van Lommel commented

2020-01-27 13:20:34 +01:00

Changed status from 'Confirmed' to: 'Archived'

Brecht Van Lommel closed this issue

2020-01-27 13:20:34 +01:00

Brecht Van Lommel self-assigned this 2020-01-27 13:20:34 +01:00

Brecht Van Lommel commented

2020-01-27 13:20:34 +01:00

Indeed not a bug in the current system, given the order in which IK constraints are applied, a second bone must be used.

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Maintain Volume constraint appears to have no effect in 2.79 #57793