How to IK rig legs

Question

I have a simple character. I would like rig the legs so that I can easily control them. How can I IK rig my characters leg?

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.blend file

Do you need reverse foot or just the simpliest IK? – Jaroslav Jerryno Novotny Dec 25 '14 at 11:53 — Jaroslav Jerryno Novotny, Dec 25 '14 at 11:53
If the foot would stay level, that would be best. – Vader Dec 25 '14 at 11:54 — Vader, Dec 25 '14 at 11:54

score 20 · Accepted Answer · edited Apr 13 '17 at 12:57

20

First you will need a target bone for the Ik - for example a copy of the foot bone. Make sure this bone is not parented to anything (except when you have a root/master bone - then parent it to root/master)

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Now in pose mode add an IK constraint to the shin bone and setup it like in the picture. You can do this fast by selecting the target_bone first (copy of foot_bone), then the shin_bone and Ctrl+Shift+C then I. Set the IK chain length to 2.

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Last step is to add Copy Rotation constraint to foot_bone.
Select target_bone (copy of foot_bone), select foot_bone,Ctrl+Shift+C then R

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Now your leg is controlled with the target bone. You can also add a Pole bone for the IK constraint so the direction of the knee is defined:

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You can eyeball the pole_angle, how to set it precisely is explained here: How to Set/Calculate pole angle of IK constraint so the chain does not move?

edited Apr 13 '17 at 12:57

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answered Dec 25 '14 at 14:15

Jaroslav Jerryno Novotny

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is foot_bone the original or the copy? – Vader Dec 25 '14 at 14:28
original - the copy is target_bone, i will edit it so its clear. – Jaroslav Jerryno Novotny Dec 25 '14 at 14:30
In the Copy Rotations constraint I can't add the new bone as the vertex group. Why is this? – Vader Dec 25 '14 at 14:38
Make sure characters armature object is in Target: input field and not some mesh object – Jaroslav Jerryno Novotny Dec 25 '14 at 15:38
Also if your leg doesn't bend correctly (remains stiff even if you move the target). Make sure to go to edit mode and give a small rotation forward to the shin bone. this will make the IK constraint work properly (kudos: https://blender.stackexchange.com/a/203683/83141) – Luca Jan 03 '23 at 14:08

How to IK rig legs

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