What I have here is the base skeleton of my rig.
It is a simple bipedal rig; not even eye/jaw/finger bones. You might notice however that there are some flat colored bones by the feet. One is the root joint at the center of the grid, and the others are part of the reverse foot, but we'll get to that in a mo.
The bones will vary in spacing/length/yadda yadda yadda, but in order to make your leg work right at all, the very least you'll need is a thigh, knee, and ankle bone. For the reverse foot, it's preferable to have a heel and toe joint as well. Make sure you have a naming convention for all your bones, as keeping track of Joints 1-3,687 will be hard.
DISCLAIMER: You will most likely never have to deal with 3,687 bones.
Once you have the base leg skeleton, you're ready to make the reverse foot bones. To differentiate them from the actual skeleton, put some marking after the name (e.g. actual skeleton: L_ankle. reverse foot skeleton: L_ankleCTRL.) Don't worry if it doesn't line up exactly like the picture. Initially, it won't. You start the chain at the heel of your character's mesh, from there make the toe, heel, and finally ankle joints. Then line up the heel joint in such a manner that the toe joint is real darn close to its final resting place, smack center with the actual toe.
WHOA! Where'd all those lines come from!? Those would be your IK Handles. I prefer to create the IK that extends the entire leg from thigh to ankle (which I name ankleIK, but something else might work for you), then go back to the other IK's once I have the RF (Reverse Foot) in place. NOTE: You are putting the IK handles on the actual skeleton, not the RF bones. Since the leg rotates more freely than the rest of the foot, you'll make the ankle IK a rotating plane (RP in the Handle Tool Settings), and the others Single something (it says SC in the Tool Settings, but heck if I remember what the "C" stands for). Make your SC IK's from the ankle to the heel, rename it ballIK, and then make your last one that goes from the heel joint to the toe joint. Now that all bones and IK's are in place, you can start connecting everything.
Select the ankleIK, then shift select the ankleCTRL bone, and parent (or "P" on your keyboard. That's the shortcut). That pattern will follow for each bone down. So, in order:
Child > Parent
ankleIK > ankleCTRL
ballIK > heelCTRL (you can name the ballIK as heelIK, if that helps you remember which is which)
toeIK > toeCTRL
They're all connected? Good, now if you select the heelCTRL and swivel it, move it, dunk it, lick it, or spank it, it should control all succeeding bones and IK handles. This setup is handy for when you need your foot to roll and twist naturally.
I hope this tutorial was helpful. I intend to continue this series as long as I can. It would be even better if someone had a specific control setup for specific body parts they wanted explained, otherwise I will continue au naturel.
