Possible IK or Driver Regression?

General Forums Blender Development Discussion
1

Hi all,

I’ve made an IK/FK switch that’s parented to the IK bone of a two bone chain. In 2.79 this works fine, but in 2.8 it causes all kinds of mischief.

There are a couple of parts to this:

  1. When in FK mode, the yellow IK bone loses its influence over the mesh and causes twitching, and the green switch bone no longer follows its parent. This can sometimes be rectified by changing in and out of edit mode or moving to a different frame, which seems to indicate some sort of cyclic dependency issue. Unparenting the switch bone fixes the problem, but that isn’t necessary in 2.79.

  2. I made the test file in 2.79, but when loaded into 2.8 the IK has no effect until I reapply the driver to the IK constraint’s influence with the exact same settings. Hence I had to make a separate 2.8 version (see below). Weirdly my earlier test files don’t exhibit this second issue.

Here are both files:
IK FK Switch 1a.blend (536.3 KB)
IK FK Switch 2_8 1a.blend (563.4 KB)

Should I report this as a bug, or is it normal behaviour that’s just become more apparent now in 2.8?

Thanks,

Chris

Human Progress
2

I would suggest to post this on devtalk.blender.org since devs do go there.

2 Likes
3

That looks broken, I would say report a bug since it’s a regression and probably something broke it.

2 Likes
4

This absolutely looks like two bugs. :smiley:

2 Likes
5

Thanks for confirming - I was going to make two separate reports, but then I found that the disabled IK issue is also fixed by unparenting the switch bone (or just adding a keyframe to it, strangely enough), so it may be related. Since this all appears to revolve around the IK switching I submitted it under the one report.