Copy rotation bone constraint behaves inconsistently on individual axis #41726

New Issue

Hjalti Hjálmarsson · 2014-09-05T15:21:16+02:00

2014-09-05 15:21:16 +02:00

System Information
Any

Blender Version
Broken: 2.71 (and earliers)

Short description of error
A bone with a copy rotation constraint (on a single axis) will have very inconsistent rotation values.

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

Check the blend file. Rotate the "hand" bone along the local Y axis and the "wrist" bone is suppose to follow along but after a few degrees it starts snapping to weird inconsistent values.

The fix is to set the "wrist" bone to "YXZ Euler" instead of the default "XYZ Euler" so the Y axis has the priority. I'm making this bug report for everyone that might stumble upon this frustrating problem and assumes that it's a bug.

Sample file: rotation_bone_bug.blend

**System Information** Any **Blender Version** Broken: 2.71 (and earliers) **Short description of error** A bone with a copy rotation constraint (on a single axis) will have very inconsistent rotation values. **Exact steps for others to reproduce the error** Based on a (as simple as possible) attached .blend file with minimum amount of steps Check the blend file. Rotate the "hand" bone along the local Y axis and the "wrist" bone is suppose to follow along but after a few degrees it starts snapping to weird inconsistent values. The fix is to set the "wrist" bone to "YXZ Euler" instead of the default "XYZ Euler" so the Y axis has the priority. I'm making this bug report for everyone that might stumble upon this frustrating problem and assumes that it's a bug. Sample file: [rotation_bone_bug.blend](https://archive.blender.org/developer/F109018/rotation_bone_bug.blend)

Hjalti Hjálmarsson commented

2014-09-05 15:21:16 +02:00

Changed status to: 'Open'

Hjalti Hjálmarsson commented

2014-09-05 15:21:16 +02:00

Added subscriber: @Hjalti

Joshua Leung was assigned by Dalai Felinto

2014-09-05 15:24:39 +02:00

Dalai Felinto commented

2014-09-05 15:24:39 +02:00

Added subscribers: @JoshuaLeung, @dfelinto

Dalai Felinto commented

2014-09-05 15:24:39 +02:00

@JoshuaLeung is this a known todo/limitation?

Bastien Montagne commented

2014-09-05 15:39:27 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2014-09-05 15:39:27 +02:00

Think you are hitting the usual infamous issue with rotations and constraints - those being handled through matrices only, you can only set them in [-180, 180] range, ultimately.

Using that on bones does not makes things easier, given how complex bones rotations are… :/

Think you are hitting the usual infamous issue with rotations and constraints - those being handled through matrices only, you can only set them in [-180, 180] range, ultimately. Using that on bones does not makes things easier, given how complex bones rotations are… :/

Joshua Leung commented

2014-09-05 15:56:21 +02:00

Yep, looks like a classic case of the rotation decomposition going wrong. I haven't seen this particular version of it before, but it'll be due to the same cause. At least a relatively "simple" workaround exists for users in this case (unlike in the other cases, where the fixes are more involved).

Bastien Montagne commented

2014-09-06 11:48:49 +02:00

Changed status from 'Open' to: 'Archived'

Bastien Montagne closed this issue

2014-09-06 11:48:49 +02:00

Bastien Montagne commented

2014-09-06 11:48:49 +02:00

Closing this as known limitation, no point in keeping it open in tracker. :)

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

Copy rotation bone constraint behaves inconsistently on individual axis #41726