Help with rigging 3x3 bones and root in blender

Question

recently I started Blender and I want to recreate a simple rig I already did in Houdini. Unfortunately I am not able to recreate my setup so I am seeking advice on several issues.

First of all I have no idea how to add an IK chain for 3 bones. When I get the workflow correctly I have to edit my Armature in Edit Mode, then select the last bone -> Pose mode and there I can assign a Inverse Kinematics Constraint. But how does it work with three bones?

I have robot parts, so I don't need any envelope or weight. My geometry could be straight parented to a bone. How does that work in blender (does it?)

Root - Chain Goal (drives the very end of the bonechain) - Bone1 - Geometry1 - Bone2 - Geometry2 - Bone3 - Geometry3

But how am I supposed to bind a chain end to an empty/circle for animating?

For a better understanding I enclosed some images what my rig needs to do. Any help, tips or links to tutorials would be highly appreciated. All I find is basic IK or guys trying to rig biped characters in 10 seconds ..

https://i.stack.imgur.com/kmGQG.gif https://i.stack.imgur.com/n95wp.gif https://i.stack.imgur.com/H5Zq4.gif

Thanks! M

Answer 1

Here is a basic solution for this kind of armature:

Extrude a bone from the lower leg, unparent it, it will be the IK target, which will control the lower leg (IK bone). Duplicate the target to make the IK pole target (the bone that will give direction to the knee), parent it to the IK target.

In Pose mode give the lower leg an Ik constraint, assign it the target and pole target, give it a Pole Angle of 180° if necessary and a Chain Length of 3.

To give your bones some custom shapes, in Object mode create an object with the shape you want (example: a circle), then back to the armature, in Pose mode, select the bone you want to shape, in the Properties panel > Bone > Viewport Display > Custom Object > select the circle.