Ian Hubert does it again... I had no idea that IK was that easy to setup. He demos it with a really cool robotic arm at the end.
Though shorts can be annoying because you can't scrub, so here's the breakdown version that includes some of the stuff he doesn't specifically say:
Basic Setup
- Add a Single Bone, go into Edit Mode, select the end point of the bone, press 'E' to extrude. Repeat a few times to make an arm.
- Switch to the Cursor tool, click just below the arm and create another bone that will act as the control bone. (Shift + A)
- Switch back to the Tweak/Select tool, select the control bone and rotate it so that it's horizontal.
- Switch over to Pose Mode, make sure the control bone is selected, then Shift + Select the bottom bone of the arm so you have two bones selected. Press Shift + I, then 'To Active Bone.'
- Now moving the control bone gives you a snazzy IK Arm.
Parenting IKs
- Switch over to Edit Mode, select all the bones of the armature, duplicate it (Shift + D) then rotate and scale it down to fit within the larger armature. (You can duplicate in a different mode, but make sure you use CTRL + J to join the armatures into one before the next step)
- Still in Edit Mode, Shift + Select the top bone of the smaller armature and the top bone of the larger armature, press CTRL + P, then 'Keep Offset,' then Shift + Select the control bone of the smaller armature and the bottom bone of the larger armature and do the same.
- Go to Pose Mode, select the bottom bone of the small armature, click into 'Bone Constraints Properties' tab in the properties panel, make sure the 'Chain Length' is set to something higher than 0.
- Now try moving the control bone of the large armature - you'll see it also moves the parented armatures... super cool.
- In the tutorial, Ian also shows adding additional constraints, such as a rotation constraint, so that the robot arm is locked to certain movements.