Press `Create` button to create this expression.
Now select r_toe joint from outliner window and template it. (Display > Object Display > Template)
Select rik_ball and rik_pelvis ikhandles and all three locators(lx_toe, lx_ball, ilx_heel)
and hide them (Display > Hide > Hide Selection)

To test the setup did so far select x_pelvis joint and move it up and down. When the foot of control leg passes the ground plane the reverse leg`s foot stays on ground and leg bends properly. You can also try to move ik_leg ikhandle to see how the reverse leg behaves when control legs bends.


Figure 4

Step 5 - Fine Tuning

Create an ikhandle from x_heel joint to x_toe joint and name it as `ik_toe`. (Skeleton > IK Handle Tool)
Group ik_toe and ik_leg handles together and name it as `foot`. (Edit > Group)
Using `Snap to Points` option, snap foot object`s local axis to ik_leg ikhandle.

To make foot object easy to select and animate, move it`s display handle a bit right.
(Select foot node, open attirube editor, check `display handle` option in display tab and close attibute editor.


Figure 5

Select Display > Hide > Hide Kinematics > Joints. Go component mode and select selection handle
and move it a bit right. Go back object mode, and select Display > Show > Show Last Hidden.)
Create a locator and move it left of skeletons.(Create > Locator)
Rename it as `pole_leg`.
Pole vector constrain rik_pelvis ikhandle to pole_leg locator. (Select pole_leg locator than select rik_pelvis ikhandle and Constrain > Pole Vector.)

Select ik_toe and ik_leg ikhandles and template them. (Display > Object Display > Template)
Select control leg`s root joint(x_pelvis) and hide it. (Display > Hide > Hide Selection)
Select reverse leg`s root joint(r_toe) and untemplate it. (Display > Object Display > Untemplate)


Figure 6

To test the setup, you can move pole_leg locator in Z axis to change leg`s twist about pelvis joint, and move or rotate foot object to pose the foot and bend leg.

Step 6 - Creating the main skeleton

Now we will create a main skeleton that will be used when skinning.

Unhide control leg. (Select x_pelvis and Display > Show > Show Selection)
Select the root joint of control leg skeleton (x_pelvis) and duplicate without any connections.(Edit > Duplicate)
Move the duplicated leg somewhere else and name joints as left_pelvis, left_knee, left_heel, left_ball and left_toe.
Set it back to the default pose. (Skeleton > Assume Preferred Angle)
Create a new three joint skeleton for spine bones and name them as root, spine1 and spine2.(Skeleton > Joint Tool)
Connect the left_pelvis joint to the root joint.
Select the left_pelvis joint and mirror it.(Skeleton > Mirror Joint)
Rename mirrored leg`s joints as right_pelvis, right_knee, right_heel, right_ball, and right toe.


Figure 7

Step 7 - Making control and reverse skeletons to drive main skeleton

In the outliner window select everything except root joint and create a group. (Edit > Group)
Rename this group as `left_leg`.
Duplicate left_leg group with upstream graph and rename it as `right_leg`. Move it a bit far in Z axis.


Figure 8

Now we will setup some constrains to make control legs and reverse legs to drive main skeleton`s legs. To do this create these constrains;

for left leg;
point constrain left_knee joint to r_knee joint of left_leg group.
point constrain left_heel joint to r_heel joint of left_leg group
point constrain left_ball joint to r_ball joint of left_leg group
point constrain left_toe joint to r_toe joint of left_leg group
point contrain x_pelvis joint of left_leg group to left_pelvis joint

and for right leg;
point constrain right_knee joint to r_knee joint of right_leg group.
point constrain right_heel joint to r_heel joint of right_leg group
point constrain right_ball joint to r_ball joint of right_leg group
point constrain right_toe joint to r_toe joint of right_leg group
point contrain x_pelvis joint of right_leg group to right_pelvis joint

Now select x_pelvis and r_toe joints of left_leg group and x_pelvis and r_toe joints of right_leg group and hide them. (Display > Hide > Hide Selection).

Rename pole_leg locator of left_leg group as `pole_left_leg` and of right_leg group as `pole_right_leg`.
Rename foot group of left_foot group as `left_foot` and of right_leg group as `right_foot`.


Figure 9


download advanced_leg_skeleton.zip


Huh!.... That`s all, have fun ;)