Animal Rigger ProIK and FK
Switch any leg between IK and FK without it moving, and switch in the middle of a shot.
Every leg has two ways to pose it:
- IK: you move the foot, and the leg bends to reach it. Use it when the foot is on the ground, or pushing against something.
- FK: you turn each bone from the top down. Use it when the leg swings freely through the air.
A walk often uses both: IK while the foot is planted, FK while it swings.
Switch a leg
On Animate, open IK / FK. Its header counts the legs, for example 3 IK · 1 FK. There is one line per leg (Front left, Front right, Hind left, Hind right) with IK and FK buttons. The pressed one is how that leg works now.
Press the other button. Before the switch, the new method's controls are moved to where the leg is, so the leg stays exactly where it was. Then the control you pose with next is shown and selected: the top leg bone in FK, the foot in IK.
It works from Object Mode too. You do not need to select a bone first.
Other ways to switch:
- All legs: IK or FK for all four at once.
- Right-click in Pose Mode › Switch IK / FK: switches the legs of the selected bones.
The arrow button at the end of each line selects the control that leg is posed with now. Shift-click it to add to the selection.
Keys
Keys decides whether a switch sets keys:
| Setting | What happens |
|---|---|
| Auto | Keys the switch when auto-keying is on, or when the leg already has keys. Otherwise sets none. The default. |
| Always | Always keys the switch. |
| Never | Only switches. |
Auto keys exactly when you need it: on an animated leg, a switch with no key would be undone as soon as you changed frame.
Switch in the middle of a shot
Go to the frame where the method should change and press the button. With a key set:
- The frames before stay as they were. If the leg had no earlier key for its method, the old method is also keyed on the frame before. Switch to FK at frame 30, and frame 29 is still IK.
- The frame you are on has the new method, with the leg in the same place.
A later switch adds its own key. Scrub across the switch to check it: the foot should not jump.
The leg's sliders
Select any control on a leg and its sliders show under the table:
| Slider | What it does |
|---|---|
| Stretch | Lets the IK leg stretch past its length to reach the foot. |
| Foot roll | Rocks the foot back on the heel, or up onto the toe. |
| Bank | Tips the foot onto its inner or outer edge. |
| Toe break | Folds the paw across the middle, so the toe can stay flat. Paws only. |
| Toe curl | Curls the toes. Paws only. |
| Toe spread | Spreads the toes. Paws only. |
Keep a foot planted
In IK, a foot's Follows setting says what it moves with. Set it to World and the foot stays put while you move the body. Pick it under The selected control on Animate with the foot selected. The switch does not make the foot move.