Arms & Clavicles
The clavicle is very important in order to get good arm movements, because the shoulder doesn't rotate more than on a horizontal line. With the clavicle, this limit can be surpassed, but remember that the clavicle bone doesn't rotate on its own axis (the one pointing to the shoulder). There is no limit on the shoulder's rotation, but the elbow can only rotate on one axis (using the biceps and triceps muscles).
The wrist bone also cannot rotate on its axis point. The relationship between the elbow and the wrist is very interesting because of the radius and ulna bones; they cross when the forearm rotates so that the wrist region rotates, keeping the elbow fixed (Fig.08).
Basically, we can consider that there are three phalanx bones for each of the five fingers in the human hand. None of these bones rotate on their axis point. The starting base of a phalanx can rotate on two axes, but the middle and last phalanges cannot (Fig.09).
The leg joint can rotate in all directions, and it's possible to rotate the ankle with it together, as if in a group. The knee just rotates in one direction, whilst the toes on the feet are similar to the fingers on the hand (with three phalanx bones for each), except that the toes only have two phalanges each (Fig.10).
Remember to base your rigging on good anatomy whenever you can, but don't let it imprison your creativity! Sometimes we need to create mechanics that are different to realistic and natural anatomy in order to achieve the desired effects and deformations. Feel free to diversify using your creativity to get the best solutions for your needs.
That's it for this lesson! Be sure to draw and study a lot of anatomy and deformations! In the next chapter we will dive into Maya - our 3D software of choice - to put our knowledge into practice! That's right, in the next part we will test our planning on the real thing! A brief overview will show you how the software works and explain some of its main tools that are used for the rigging process, and we will also discover some tips and tricks on general rigging so you can speed up your workflow.