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Sticky Option in Floor Constraint for Bones Not Working
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Description

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: Intel(R) HD Graphics 520 Intel 4.5.0 - Build 25.20.100.6373

Blender Version
Broken: version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-09 21:43, hash: rB030c7df19da9
Worked: (optional)

Short description of error
The sticky option of the floor constraint does not work. I tried to use it in Blender 2.79 and it worked fine, so I'm pretty sure it's not user error on my end.

Exact steps for others to reproduce the error
The attached Blend file has a bone set up above a plane with it as its floor and the sticky option marked, but, if you try to move it across the floor, it will not stick. This is a new Blender file that I made specifically for this so there are not really many extra details involved. I created a plane object and then scaled it up. I then made a bone (raised it a little) and applied the bone constraint and checked "Sticky".

Event Timeline

you forgot to attach the .blend file :)

Brecht Van Lommel (brecht) triaged this task as Needs Information from User priority.Jun 10 2019, 11:22 AM
Brecht Van Lommel (brecht) raised the priority of this task from Needs Information from User to Needs Triage by Developer.Jun 19 2019, 11:06 PM
Sebastian Parborg (zeddb) triaged this task as Confirmed, Medium priority.

@Brecht Van Lommel (brecht) Sergey and I looked into this and this is really old feature that never really worked reliably. The initial commit from 2005 even states as much.

The sticky option is dependent on time and will break when jumping around the timeline (or during frame skip etc).

Because of CoW, the code in question doesn't work at all right now because constraints can't save data or manipulate it's own data during evaluation.
(Which is intentional)

Yes, I think it can be removed.

Brecht Van Lommel (brecht) lowered the priority of this task from Confirmed, Medium to Confirmed, Low.