IK-Stretching no longer stretches on Y-Axis #52747

New Issue

Derek Gomen · 2017-09-14T10:09:32+02:00

Derek Gomen commented

2017-09-14 10:09:32 +02:00

System Information
OS: Windows 10 64-bit
GPU: NVIDIA GeForce GTX 1070 x2
RAM: 16GB DDR3
CPU: AMD FX-8350

Blender Version
Broken: 2.79 (6f633de)
Worked: Latest stable 2.78 release. Also worked in the 2.78.5 (7b25ffb) experimental build that included the 2.79 features for Denoising and the Principled Shader

Short description of error
Introduced in 2.78, enabling stretching in the [IK settings ]] (the bottom slider) allowed bones to stretch only on the Y-Axis. I took advantage of this heavily when I found out about this, but in any 2.79 version released up to this point, the stretching seems to have reverted back to how it worked before 2.78 where bones will enlarge on all axis. This can be seen in this [ https:*www.youtube.com/watch?v=GeCnJiAb5e4 | Youtube Video . This stretching reverting back is breaking all of my animations I have done in the past year as the limbs now awkwardly enlarge when I originally had them stretch only on the Y-Axis.

Exact steps for others to reproduce the error
SimpleIKStretch.blend

Create a simple IK rig. Only two bones are necessary. The deform bone, and the IK bone.
Enable IK stretching by moving the stretching slider to be above 0.00.
In most versions of 2.78, the base deform bone should only stretch along the bone's local y-axis. In the latest stable and development version of 2.79, the base deform bone will simply just enlarge (scale) on all local axis.

**System Information** OS: Windows 10 64-bit GPU: NVIDIA GeForce GTX 1070 x2 RAM: 16GB DDR3 CPU: AMD FX-8350 **Blender Version** Broken: 2.79 (6f633de) Worked: Latest stable 2.78 release. Also worked in the 2.78.5 (7b25ffb) experimental build that included the 2.79 features for Denoising and the Principled Shader **Short description of error** Introduced in 2.78, enabling stretching in the [IK settings ]] (the bottom slider) allowed bones to stretch only on the Y-Axis. I took advantage of this heavily when I found out about this, but in any 2.79 version released up to this point, the stretching seems to have reverted back to how it worked before 2.78 where bones will enlarge on all axis. This can be seen in this [[ https:*www.youtube.com/watch?v=GeCnJiAb5e4 | Youtube Video ](https:*i.stack.imgur.com/C3O4P.png). This stretching reverting back is breaking all of my animations I have done in the past year as the limbs now awkwardly enlarge when I originally had them stretch only on the Y-Axis. **Exact steps for others to reproduce the error** [SimpleIKStretch.blend](https://archive.blender.org/developer/F797865/SimpleIKStretch.blend) - Create a simple IK rig. Only two bones are necessary. The deform bone, and the IK bone. - Enable [IK stretching ](https://i.stack.imgur.com/C3O4P.png) by moving the stretching slider to be above 0.00. - In most versions of 2.78, the base deform bone should only stretch along the bone's local y-axis. In the latest stable and development version of 2.79, the base deform bone will simply just enlarge (scale) on all local axis.

Derek Gomen commented

2017-09-14 10:09:32 +02:00

Changed status to: 'Open'

Derek Gomen commented

2017-09-14 10:09:32 +02:00

Added subscriber: @DerekGomen

Joshua Leung commented

2017-09-14 13:25:02 +02:00

Added subscriber: @JoshuaLeung

Joshua Leung commented

2017-09-14 13:25:02 +02:00

Changed status from 'Open' to: 'Archived'

Joshua Leung closed this issue

2017-09-14 13:25:02 +02:00

Joshua Leung self-assigned this 2017-09-14 13:25:02 +02:00

Joshua Leung commented

2017-09-14 13:25:02 +02:00

Thank you for your report. Unfortunately, we've had to change the way that the IK-stretching with non-uniform scale is working in order to fix several critical bugs the 2.78 method was causing.

The new (2.79) behaviour intentionally aims to be more similar to the old (pre-2.78) behaviour. This is because the 2.78 behaviour was causing significant breakage issues with multiple rigs in critical ways (e.g., IK <-> FK switching was broken on those rigs, along with several other built-in tools). For more details, see #51971 and blender/blender-addons#51930, and the related commits fixing those issues.

Apologies for the file breakage that these changes have caused. As noted on the release notes, we did expect that some rigs would be broken by this change.

As for your rigs, here is a setup that you could use instead:
SimpleIKStretch-fixed.blend

The "B1-Copy" and "B2-Copy" bones copy the transforms from the IK chain bones, while excluding the X and Z scaling. The geometry in turn is only deformed by these two new "deformer" bones, instead of by the IK bones directly. Hope this helps.

Thank you for your report. Unfortunately, we've had to change the way that the IK-stretching with non-uniform scale is working in order to fix several critical bugs the 2.78 method was causing. The new (2.79) behaviour intentionally aims to be more similar to the old (pre-2.78) behaviour. This is because the 2.78 behaviour was causing significant breakage issues with multiple rigs in critical ways (e.g., IK <-> FK switching was broken on those rigs, along with several other built-in tools). For more details, see #51971 and blender/blender-addons#51930, and the related commits fixing those issues. Apologies for the file breakage that these changes have caused. As noted on the release notes, we did expect that some rigs would be broken by this change. As for your rigs, here is a setup that you could use instead: [SimpleIKStretch-fixed.blend](https://archive.blender.org/developer/F798583/SimpleIKStretch-fixed.blend) The "B1-Copy" and "B2-Copy" bones copy the transforms from the IK chain bones, while excluding the X and Z scaling. The geometry in turn is only deformed by these two new "deformer" bones, instead of by the IK bones directly. Hope this helps.

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IK-Stretching no longer stretches on Y-Axis #52747