Rigging & Skinning 101 - Legs & Feet

Legs & Feet

The Image below shows a leg skeleton. The spheres are joints, the triangles are bones. The bones are only visual but show the direction of the hierarchy of the limb.

Position, scale and rotation are three aspects of a rig to keep in mind. Rotation is very important.

Holding x will lock the grid and create a 0 rotation for the joint being created. This is arbitrary but important, as '0' keeps the rig clean.  

The leg in the image below has a hierarchy of 5 joints on a total of 11 grid units.

Labelling joints creates a smooth workflow and easy to read, the process becomes simpler in the long run. 

A pelvis joint can now be added to the leg skeleton. This is parented to the child joint, the hip. The parenting process is done automatically with the rest of the leg. The parenting is indicated by the position of the bone, which points towards the child from the parent. 

The image below shows the Creation of Rotation plane IK handles.

Maya understands offset joints and creates IK movements accordingly. The knee reacts to the upwards movement of the ik handle because this joint was made offset from the hip and foot joints.

This rig is an Inverse kinematic, this allows a rig to react more realistically.

Creating groups and changing the position of the group’s pivot point creates specific movement and rotation. In this example, each group in the outliner tab controls a separate foot movement.  These groups are labelled accordingly, similarly to how the joints have been labelled for efficiency when working.

Controls can be added once IK rotation groups have been created.

Controls are easier to indicate if their shape represents the anatomy. For example, a control in the shape of a footprint.

Joints have priority over everything else, these can be hidden to prevent changing them by mistake.

The history needs to be deleted and the transformations frozen on the primitive shape controls. This is very important as it can affect the movement of the rig. 

In the constrain menu: Point controls translate, Orient controls rotate, and Scale controls scale. Toggling these can adapt a control.

A pole vector constraint causes the end of a pole vector to move to and follow the position of an object, or the average position of several objects.

Driven keys create an association between pairs of attributes, where one attribute value (or multiple attributes values) drive the value of another.

The driver will always be for our controls. The driven is for groups

To clean up the ‘driven keys’ that have been applied, we can cap the numbers we can scrub between, removing numbers that don’t affect anything. Now, if a control has a maximum scrub of 30, you can’t scrub higher than that number. This makes movement easier to adjust.

At this stage, we can move on to the spine. The legs are mostly completed.