IK is stupidly useful for keeping your animation planted on the ground, though using it for animating might be tricky. I'm no expert on this, so try it out yourself.
I also recommend setting this up before you start animating so you don't mess up your previously finished frames.
Heres an example on setting up the IK rig on the legs of an animation
1. Load your ani and do whatever pre-animation setup you need to do
2. Find the bones "%leg1r" and "%footr" for the right foot, and "%leg1l" and "footl" for the left. Isolate it if you need to. Make sure you can click it.
3. Select the leg1l/r bone and go to Animation -> IK Solvers -> IK Limb Solver
4. On the viewport, your mouse now has a dotted line coming from the leg bone, click on the foot bone that is on the same side as your leg. (I think this can be done in the Scene Explorer)
5. Now the leg has an IK solver attached to it. The IK Handle is a blue + object that should be centered on the foot bone. Move it around and check that the leg bends properly forward.
5a. If the foot doesn't bend properly, Undo the Solver away, give the "leg1" a little bend forward (along the Y axis), "leg2" a little bend back (along the Y axis, I recommend using Local rotation instead of View rotation), and remake the IK Limb Solver. This will help the solver know which way to bend.
Move the IK handle around and you'll see that the leg can now rotate in forward, backwards, and side to side. The only thing missing is the rotation inwards and outwards, which the Command Panel can help with.
1. Select your IK Handle
2. Click on the Motion tab (1) and scroll down till you see the IK Solver (2) and/or IK Solver Properties box (3)
In the
IK Solver mini-panel has a drop for the solve you wish to use. More info of the solver here
here. Use IKLimb if you're not sure. The "Enabled" button will enable the IK to set Preferred Angles properties on your bones. The "IK for FK pose" box will allow you to move the handle around AND allow you to rotate the bone to animate in FK. IK/FK Snap will snap the IK handle to where the end Joint Bone. The buttons in the Preferred Angles I haven't explored yet. Bone Joints is the bones you're solving.
In the
IK Solver Properties mini-panel, is what rotates the leg inwards and outwards. Just click and drag the "Swivel Angle" number box up and down to rotate it inwards and/or outwards. Make sure the parent space is in the Start Joint. Try not to rotate like crazy (like to -720).
When you have an angle you like, you need to key the rotations on the bones.
I'm still not sure what the proper way is doing it (probably something about those preferred angle buttons), but what I do is I move the IK to where I need the leg to be and manually key the rotation on every bone along the leg. Then I click back on the handle and disable IK solver. If the leg doesn't flip to some weird angle, then I'm good.