iTaSC IK solving strange behavoir after scaling in object mode #31588

Closed
opened 2012-05-25 00:29:09 +02:00 by Matt Hoecker · 4 comments

%%%Blender 2.63a Official Release (Though my splash screen doesn't say 2.63a, just 2.63, I did a fresh install just to make sure.)
Windows 7 64bit
Ncidia GeForce GTS 450

When using the new iTaSC IK solver I ran into this problem:

When I scale the armature object, any IK solver already added, or added after scaling, gives inconsistent results such as:

Head of effector bone will snap to the midpoint of the previous bone in the chain. (when chain length is 2 and scaled down)
Bones spread out with great distance between (when scaled up).

However, when chain length is set to 1, the effector bone operates, seemingly, as it should.

It took me several hours of testing to figure out just how this was happening, but I got it down to a repeatable offense.

Default Scene, add armature.
Extrude a chain of bones.
Add a target (bone or empty, but bone is easier to see the [I believe] incorrect effect)
In Armature Object data for the armature, under iTaSC parameters, set to iTaSC (Animation or Simulation, doesn't matter).
Add inverse kinematic constraint to last bone and target it to your target.
Test. It should work fine.
Change chain length, it should work fine.
Now, IN OBJECT MODE scale down the armature, just slightly. Pose the target bone and you can start to see the effect.
Scale down the armature to .5 its size and move the target bone. Play with chain length.
Scaling up gives a spread out bone effect.

Maybe this is actually something that is supposed to happen due to the math and world vs local space involved.
As I was writing this, I did find that by applying scale the armature does behave as normal. So again, this could be just the way this feature has to work, but as I was trying to use iTaSC, I spent a couple of hours of frustration trying to figure out why it was acting so strangely.

Do with this info what you will! Thanks for your hard work.

%%%

%%%Blender 2.63a Official Release (Though my splash screen doesn't say 2.63a, just 2.63, I did a fresh install just to make sure.) Windows 7 64bit Ncidia GeForce GTS 450 When using the new iTaSC IK solver I ran into this problem: When I scale the armature object, any IK solver already added, or added after scaling, gives inconsistent results such as: Head of effector bone will snap to the midpoint of the previous bone in the chain. (when chain length is 2 and scaled down) Bones spread out with great distance between (when scaled up). However, when chain length is set to 1, the effector bone operates, seemingly, as it should. It took me several hours of testing to figure out just how this was happening, but I got it down to a repeatable offense. Default Scene, add armature. Extrude a chain of bones. Add a target (bone or empty, but bone is easier to see the [I believe] incorrect effect) In Armature Object data for the armature, under iTaSC parameters, set to iTaSC (Animation or Simulation, doesn't matter). Add inverse kinematic constraint to last bone and target it to your target. Test. It should work fine. Change chain length, it should work fine. Now, IN OBJECT MODE scale down the armature, just slightly. Pose the target bone and you can start to see the effect. Scale down the armature to .5 its size and move the target bone. Play with chain length. Scaling up gives a spread out bone effect. Maybe this is actually something that is supposed to happen due to the math and world vs local space involved. As I was writing this, I did find that by applying scale the armature does behave as normal. So again, this could be just the way this feature has to work, but as I was trying to use iTaSC, I spent a couple of hours of frustration trying to figure out why it was acting so strangely. Do with this info what you will! Thanks for your hard work. %%%
Author

Changed status to: 'Open'

Changed status to: 'Open'
Member

%%%Thanks for the report. I've reproduced the bug and will look into it. Obviously iTaSC does not take the object scale factor into account. Shouldn't be difficult to fix.

Note that I had first to fix a series of crash related to unaligned memory in Eigen3. It looks like iTaSC was never tested with SSE optimization.%%%

%%%Thanks for the report. I've reproduced the bug and will look into it. Obviously iTaSC does not take the object scale factor into account. Shouldn't be difficult to fix. Note that I had first to fix a series of crash related to unaligned memory in Eigen3. It looks like iTaSC was never tested with SSE optimization.%%%
Member

%%%Fixed in revision 47372%%%

%%%Fixed in revision 47372%%%
Member

Changed status from 'Open' to: 'Resolved'

Changed status from 'Open' to: 'Resolved'
Sign in to join this conversation.
No Label
Interest
Alembic
Interest
Animation & Rigging
Interest
Asset Browser
Interest
Asset Browser Project Overview
Interest
Audio
Interest
Automated Testing
Interest
Blender Asset Bundle
Interest
BlendFile
Interest
Collada
Interest
Compatibility
Interest
Compositing
Interest
Core
Interest
Cycles
Interest
Dependency Graph
Interest
Development Management
Interest
EEVEE
Interest
EEVEE & Viewport
Interest
Freestyle
Interest
Geometry Nodes
Interest
Grease Pencil
Interest
ID Management
Interest
Images & Movies
Interest
Import Export
Interest
Line Art
Interest
Masking
Interest
Metal
Interest
Modeling
Interest
Modifiers
Interest
Motion Tracking
Interest
Nodes & Physics
Interest
OpenGL
Interest
Overlay
Interest
Overrides
Interest
Performance
Interest
Physics
Interest
Pipeline, Assets & IO
Interest
Platforms, Builds & Tests
Interest
Python API
Interest
Render & Cycles
Interest
Render Pipeline
Interest
Sculpt, Paint & Texture
Interest
Text Editor
Interest
Translations
Interest
Triaging
Interest
Undo
Interest
USD
Interest
User Interface
Interest
UV Editing
Interest
VFX & Video
Interest
Video Sequencer
Interest
Virtual Reality
Interest
Vulkan
Interest
Wayland
Interest
Workbench
Legacy
Blender 2.8 Project
Legacy
Milestone 1: Basic, Local Asset Browser
Legacy
OpenGL Error
Meta
Good First Issue
Meta
Papercut
Meta
Retrospective
Meta
Security
Module
Animation & Rigging
Module
Core
Module
Development Management
Module
EEVEE & Viewport
Module
Grease Pencil
Module
Modeling
Module
Nodes & Physics
Module
Pipeline, Assets & IO
Module
Platforms, Builds & Tests
Module
Python API
Module
Render & Cycles
Module
Sculpt, Paint & Texture
Module
Triaging
Module
User Interface
Module
VFX & Video
Platform
FreeBSD
Platform
Linux
Platform
macOS
Platform
Windows
Priority
High
Priority
Low
Priority
Normal
Priority
Unbreak Now!
Status
Archived
Status
Confirmed
Status
Duplicate
Status
Needs Info from Developers
Status
Needs Information from User
Status
Needs Triage
Status
Resolved
Type
Bug
Type
Design
Type
Known Issue
Type
Patch
Type
Report
Type
To Do
No Milestone
No project
No Assignees
2 Participants
Notifications
Due Date
The due date is invalid or out of range. Please use the format 'yyyy-mm-dd'.

No due date set.

Dependencies

No dependencies set.

Reference: blender/blender#31588
No description provided.