Setting up the leg IK controls

00:03

If this were a normal biped leg,

00:06

then we would pretty much use the same IK setup that we created for the arm.

00:11

This limb is a little different though because it's

00:13

made up of three sections instead of two.

00:16

So it's classed as a quadruped limb.

00:20

What I'm going to do here is use my personal favorite setup,

00:23

but it may be that one of the other configurations better complements your own rig.

00:29

OK.

00:30

So I've already updated the controls, visibility,

00:32

so they change with the attribute.

00:35

So the IK and FK controls show and hide when needed.

00:40

I've also added this extra hock control here

00:44

and this is simply parented to the foot control.

00:47

OK. Let's find the main IK and FK joints

00:52

and hide the FK ones.

00:54

What we need is another set of joints,

00:56

ones which will help to drive the quadruped leg.

01:00

So use control and D to quickly duplicate the thigh IK joint

01:05

and then delete the tours.

01:08

We just need the four main joints.

01:11

Now rename these changing IK to driver.

01:16

OK. Let's isolate these. Now,

01:19

what we now need is another I

01:21

handle,

01:22

but this time we're going to use a spring solver.

01:25

You can also use a rotate plane solver too. If you prefer.

01:31

Actually, let's create one of those first. So we can compare

01:34

so create it from the first joint down to the very last joint.

01:39

If we move the IK handle,

01:41

now you will see that the lower leg compresses more than the upper section.

01:45

So this is OK, but it's not perfect.

01:49

Let's undo that.

01:51

And now let's create a spring solver.

01:55

You see, we now have a much nicer and more predictable compression

01:59

throughout the whole leg.

02:01

One thing to point out is that the spring solver isn't always available as an option.

02:06

If you don't see it, all you need to do is activate it.

02:10

You can do this in the script editor using a simple command

02:13

IK spring silver.

02:17

What you can also do with a spring solver is adjust the spring angle bias here

02:23

using the ramp, we can adjust how the leg compresses.

02:28

So on a more advanced rig,

02:29

we could wire this up to some controls to give

02:32

the animator the option to further fine tune the poses.

02:36

Now the spring silver is great in some situations,

02:39

but it won't always work with every rig.

02:41

It can be a little temperamental.

02:44

Let's rename this to driver left I care handle

02:48

and bring the rest of the rig back.

02:51

We are just going to parent the ICA handle to the foot control. So select it and press P

02:58

the driver leg. Now moves with the control.