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ITaSC IK constraints stop working after deleting bone inside chain and recreating it again
Open, Needs Triage by DeveloperPublic

Description

System Information
Operating system: Windows-8.1-6.3.9600 64 Bits
Graphics card: GeForce GT 730/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.12

Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: rB26bd5ebd42e3

Short description of error
When I add multiple ITaSC IK to the bone chain they doesn't work (moving IK target have no effect) if bones were created in order that is different from parenting order

Exact steps for others to reproduce the error

Inside the Top Armature I added single bone then subdivided it, then rearranged endpoints and added IK targets (blue) and IK constraints. Both IK work on this armature.

I created Bottom Armature duplicating Top Armature. Then I deleted Bone.002 and recreated it, then added IK constraint on bone Bone.002 again. While Top and Bottom armatures looks same and bones have same parenting order, both IK on Bottom Armature stop working.

Details

Type
Bug

Event Timeline

Is this a valid setup in iTaSC? It certainly doesn't look like it's predicatably working in the top armature either - in both armatures, if you reduce the chainlength of the tip IK solver from 4 to 3 so the too IKs don't 'collide' it works fine.
It could be that this is just not a supported configuration - I don't know enough about iTaSC but it would be in standard IK.
(aside - does anyone use or develop the iTaSC solver? is it a candidate for removal?)

@bassam kurdali (bassamk) @Benoit Bolsee (ben2610) develop its integration to Blender, I don't think he has much time later, but if iTaSC is working, I don't see why to remove it.

@bassam kurdali (bassamk) You may be right that the way how I rigged armature is unsupported. It could be this is right way to create that kind of rig (on blender manual it called Tree-IK and the idea is that one IK can affect another, so chainlengths can overlap)


(if it done like this, it always works and it has same functionality)
So perhaps it's not a bug.

if it has an active developer it seems fine to keep )