Error on stretched Pole Target IK
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Description

System Information
Windows 7 64, GTX 980

Blender Version
Broken: bbf09d9 (2.73a) + 691cb61

Short description of error
Bone Constraint:
IK Stretch doesnt work combined with a Pole Target - Stretch scales to zero.

I dont know if this is a bug, but havent found something on the wiki about this behaviour.

Exact steps for others to reproduce the error

IKStretchPoleBug.blend695 KBDownload

Steps: (IK Setup)

Create an Armature
- Create 3 Bones
  - Use 1 for IK-Solver Constraint
  - Use 2 as IK-Target
  - Use 3 as Pole Target

Select IK-Solver Bone
- Go to Properties > Bone > Inverse Kinematics
- Fill Stretch bar to 1.000

Problem:
The IK-Solver Bone disappears, i guess because of zero scaling and mainly because of the Pole target.

Using the Stretch Bone as part of a at least 2 part IK chain works fine.
But for some reason it dont work with a single bone setup.

rB Blender
	rB726727191ab6 Fix T43715: IK pole target + stretch not working for a single bone chain.

Mentioned Here: rBbbf09d9ee68d: Point 2.73a release to updated addons revision
rB691cb61835dc: Fix for another missing update from GPencil in Outliner

Karja Krähwald (karja) raised the priority of this task from to 90.

It seems IK stretch loses its target completely if a Pole target is assigned.
Check this by reducing the constraint influence.

I can reproduce this bug, if IK chain is only 1 bone.
Works fine with 2+ bones chain.
Works fine with 1 bone chain, but without pole.

--> KO for 1 bone chain with pole.

@Brecht Van Lommel (brecht), git blame says you did quite some work on this. Any chance you can look into this? *cateyes*

Julian Eisel (Severin) lowered the priority of this task from 90 to Normal.

Fixed now, thanks for the report.