Maniphest T82267

Animated Chain Length of IK Constraint works wrong
Confirmed, NormalKNOWN ISSUE
Actions

Assigned To
None
Authored By
Cho Dae Hwan (cutycutyhyaline)
Oct 30 2020, 10:09 PM
Tags
  • BF Blender
  • Animation & Rigging
Subscribers
Cho Dae Hwan (cutycutyhyaline)
Philipp Oeser (lichtwerk)
Sybren A. Stüvel (sybren)

Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 457.09

Blender Version
Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: rB3e85bb34d0d7
Broken: 2.80
worked: 2.79b

Short description of error

  • If insert two or more keyframes with different values with Chain Length in IK Constraint, at armature,
  • Changed value of Chain Length of IK Constraint does not applied on animation.
  • IK Constraint does not work in certain frames at all.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]

Sorry for not short. If you open attacted blender file, you can see reproduced status at last step below.

reproduce_ik.blend645 KBDownload

To Reproduce:

  • delete all object in scene.
  • turn snap on (Shift+Tab)
  • add cube.
  • move cube 5m along z axis.
  • add armature.
  • go to edit mode, with armature selected.
  • set pivot point as 3d cursor.
  • scale bone to 4 times up.
  • subdivide bone, set Number of Cuts as 3. You will get 4 bones.
  • go to pose mode.
  • select bone at top. (Bone.001)
  • add IK Constraint.
  • In IK Constraint setting, set target as cube.
  • In IK Constraint setting, set Chain Length as 3
  • go to object mode
  • set pivot point as Active Element.
  • select cube.
  • move Playhead to frame 1 in TimeLine
  • move cube -2m along x axis.
  • insert keyframe, location.
  • move Playhead to frame 30 in TimeLine
  • move cube 4m along x axis.
  • insert keyframe, location.
  • move Playhead to frame 60 in TimeLine
  • move cube -4m along x axis.
  • insert keyframe, location.
  • In TimeLine, Set Preview range from frame 1 to frame 60 (Ctrl+Alt+P)
  • Change editor type of TimeLine to Dopesheet.
  • Turn on "Show Hidden" Option in Header of Dope Sheet.
  • Turn off "Only Show Selected" Option in Header of Dope Sheet.
  • select armature
  • go to pose mode
  • select bone on top (Bone.001)
  • move Playhead to frame 1 in TimeLine.
  • insert keyframe with Chain Length in IK Constraint. (press i key with placing mouse cursor on Chain Length)

At this moment, animation works well. If you play animation, you can see top three bones moving with cube, as normal.

  • move Playhead to frame 20 in TimeLine.
  • change value of Chain Length to 2 in IK Constraint.
  • insert keyframe with Chain Length in IK Constraint.

From now, only two bone will be moving. and in earlyer frame, none of bone moving.
Expected: In frame 1 to frame 20, three bone moving, and after frame 20, two bone moving.

  • move Playhead to frame 40 in TimeLine.
  • change value of Chain Length to 1 in IK Constraint.
  • insert keyframe with Chain Length in IK Constraint.
  • Play animation (Space) and Observe animation of bones.

from now, only one bone will be moving, after frame 30. before frame 30, all bones does not move.
Expected: In frame 1 to frame 20, three bone moving, In frame 20 to frame 40, two bone moving. In frame 40 to frame 60, one bone moving.

In Addition, If you delete all keyframes of armature except frame 1 (value of Chain Length is 3), then you can see IK Constraint does not work at all.

Related Objects

Event Timeline

Cho Dae Hwan (cutycutyhyaline) created this task.Oct 30 2020, 10:09 PM
Cho Dae Hwan (cutycutyhyaline) renamed this task from If insert keyframes with Chain Length of IK Constraint, at different frames, IK works wrong. to If insert two or more keyframes with Chain Length of IK Constraint, at different frames, IK works wrong..Oct 30 2020, 10:14 PM
Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Confirmed.Nov 2 2020, 2:00 PM
Philipp Oeser (lichtwerk) added a project: Animation & Rigging.
Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Bug".
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).

Can confirm, this was working fine in 2.79

Philipp Oeser (lichtwerk) renamed this task from If insert two or more keyframes with Chain Length of IK Constraint, at different frames, IK works wrong. to Animated Chain Length of IK Constraint works wrong.Nov 2 2020, 2:01 PM
Philipp Oeser (lichtwerk) updated the task description.
Sybren A. Stüvel (sybren) moved this task from Backlog to Bugs on the Animation & Rigging board.Nov 2 2020, 4:23 PM
Philipp Oeser (lichtwerk) mentioned this in T96203: IK chain length cannot be animated.Mar 7 2022, 5:23 PM
Sybren A. Stüvel (sybren) changed the subtype of this task from "Bug" to "Known Issue".Nov 28 2022, 3:02 PM
Sybren A. Stüvel (sybren) moved this task from Bugs to Known Issues on the Animation & Rigging board.
Sybren A. Stüvel (sybren) added a subscriber: Sybren A. Stüvel (sybren).

Since Blender 3.2, the IK chain length is no longer animatable. I'll file this as a "known limitation", as it is something that would be nice to have more flexibility in. It's not something that'll be addressed soon, though.