broken IK #41097

New Issue

Skylyn Bilén · 2014-07-16T05:29:58+02:00

Skylyn Bilén commented

2014-07-16 05:29:58 +02:00

System Information
windows 7 professional
dell inspiron n5010

Blender Version
Broken:2.7.1 9337574
Worked:2.6.x

IK is improperly directing the bone when the bone is limited.

Exact steps for others to reproduce the error
build an armature, make a thing to IK. IK the bone set. limit the rotation to mimic a knee.then move the target.
the frames are right next to each other, as illustrated by the frame #'s

broken.blend

**System Information** windows 7 professional dell inspiron n5010 **Blender Version** Broken:2.7.1 9337574 Worked:2.6.x IK is improperly directing the bone when the bone is limited. **Exact steps for others to reproduce the error** build an armature, make a thing to IK. IK the bone set. limit the rotation to mimic a knee.then move the target. the frames are right next to each other, as illustrated by the frame #'s ![undefined](https://archive.blender.org/developer/F98051/undefined) ![undefined](https://archive.blender.org/developer/F98054/undefined) [broken.blend](https://archive.blender.org/developer/F98063/broken.blend)

Skylyn Bilén commented

2014-07-16 05:29:58 +02:00

Changed status to: 'Open'

Skylyn Bilén commented

2014-07-16 05:29:58 +02:00

Added subscriber: @skyliner_369

blender-admin commented

2014-07-16 05:29:58 +02:00

#41096 was marked as duplicate of this issue

Thomas Dinges commented

2014-07-16 07:31:59 +02:00

Added subscriber: @the_randomizer

Thomas Dinges commented

2014-07-16 07:31:59 +02:00

◀ Merged tasks: #41096.

Bastien Montagne commented

2014-07-17 20:13:19 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2014-07-17 20:13:19 +02:00

As usual, please always attach a simple .blend file to help reproducing the issue…

Skylyn Bilén commented

2014-07-18 07:52:37 +02:00

you do realize that there is a very simple blend file at the bottom of the page.

Bastien Montagne commented

2014-07-18 09:47:35 +02:00

Woops… Sorry, can confirm the issue indeed :/

Brandt commented

2014-07-18 10:38:03 +02:00

That's all right, my friend and I wanted to make sure it was reported promptly :)

Brecht Van Lommel commented

2014-07-19 15:09:39 +02:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2014-07-19 15:09:39 +02:00

Brecht Van Lommel self-assigned this 2014-07-19 15:09:39 +02:00

Brecht Van Lommel commented

2014-07-19 15:09:39 +02:00

This is a bit of a weakness in the IK solver which is not considered a bug currently. To get it to behave as you want you have to very slightly bend the joints a bit to hint in which direction you want them to go.

So instead of forming a straight line, change the rest pose so that the knee is bent just a bit, and it should behave more reliable.

This is a bit of a weakness in the IK solver which is not considered a bug currently. To get it to behave as you want you have to very slightly bend the joints a bit to hint in which direction you want them to go. So instead of forming a straight line, change the rest pose so that the knee is bent just a bit, and it should behave more reliable.

Brecht Van Lommel commented

2014-07-19 15:11:08 +02:00

Also, this is good practice in general even if this problem was solved. There are many situations in which multiple solution are possible given a particular target position. So to get predictable behavior it's best to never have perfectly straight lines in the rest pose.

Skylyn Bilén commented

2014-07-19 19:15:44 +02:00

well, if it is a weakness, they should still work on it. this seems to be a good point for the ik to start to be even better. the solver should easily be able to find the solution, even if the bones aren't bent. on top of that, the character modeled had had knees locked. the solver needs this fixed.

Brandt commented

2014-07-19 19:20:24 +02:00

I agree with Skyliner_369 said, this is clearly an issue that should be looked into more. Flaw or not, it's something that should not be happening and should not have to be worked around. I'm sorry, but I simply cannot agree that the issue cannot be resolved. This is not a very professional way to handle issue, please reconsider and look into this. Unresolved issues or flaws should not be left in this state.

Brecht Van Lommel commented

2014-07-19 19:26:37 +02:00

We have a strict policy for bugs, and that is when a feature is not working as intended by the developer. This could be improved but it would be considered a feature request, and we do not handle those here.

You'll find the same advice for rigging in Autodesk Maya for example, it's really not unusual, it's basic rigging practice.

We have a strict policy for bugs, and that is when a feature is not working as intended by the developer. This could be improved but it would be considered a feature request, and we do not handle those here. You'll find the same advice for rigging in Autodesk Maya for example, it's really not unusual, it's basic rigging practice.

Brandt commented

2014-07-19 22:58:11 +02:00

Well, wish we knew that beforehand, now it feels like I did nothing but waste your guys' time, as usual :( Guess I just aren't that good at the program, like, at all.

Brecht Van Lommel commented

2014-07-19 23:24:24 +02:00

It's no problem, thanks for taking the time to report, for this kind of thing it's not always clear if it is a bug or not and the behavior is of course not optimal. Just a regular part of bug reporting and development.

Brandt commented

2014-07-19 23:26:47 +02:00

So what can we do to overcome or circumvent the issue?

Brecht Van Lommel commented

2014-07-19 23:32:06 +02:00

Make sure the bones are not in a straight line, bend the knee a tiny bit.

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broken IK #41097