Lesson learnt 004 - Vanilla walk cycle

This is a simple walk cycle or vanilla walk cycle assignment from Animation Mentor.

The Vanilla Walk

A typical Vanilla walk or a relaxed walk will have a speed of 24 frames per cycle.

Concept

So, what makes a walk possible? What is a walk?

A walk is a series of controlled falls. When a body's Centre of Gravity (CG) is tilted by leaning forward, it should fall forward. While the body falls, a feet moves forward and contacts the ground, which balance the weight shift or CG. But not totally balanced (if not the walk will stop), still leaving some CG tilt, the body continues moving forward and the next feet takes over the balance. Therefore one importance note is that the body continuously tilts forward throughout the walk. The diagram below illustrates from left to right.

But of course if it is a Characteristic walk then the concept will be different. Below is an example where the legs are the driver of the CG forward instead of the body.

Breakdown

The Concept above is a basic description of a walk. For more detailed and complete analysis, lets get into the breakdowns.

Each cycle of 24 frames starts from one foot forward, transit to the other leg and back again. So each 12 frames is actually a symmetry of the other leg cycle. In this 12 frames there is a the ground Contact of one foot forward and one foot backwards, follow by a Passing of the rear foot to the front and then another ground Contact of that foot. It is further break down into in-betweens namely Extreme High and Extreme Low. Take note on the Extreme Low, the legs bend so the body actually dips in height a little. While at Extreme High, the leg is straightened and the toes are tipped and so the body raises.

This is just the beginning, as if it is not complicated enough..

If the character that is animated has both legs starting from one same point then this animation would sufficient. But if the legs starts from 2 different points, as in a hip, then there is more to go.

Weight Shift

When the body is supported by both legs, in Contact pose, the weight is distributed equally to both sides, so the hips is flat. 

During the transition to the Passing pose, where one leg is lifted up, all the weight is now shifted to the other leg and to the hips. So to balance and not fall side ways, the hips shifts sideways, bringing the CG back to the centre (may not need to be totally back to centre because soon the other leg will contact), as well as tilt up one side because of weight acting on it.

More Hips Rotation

Other then the hips raising and dropping from the side by RZ to take the weight, there are 2 more rotation axis. 1st is RY axis, where turning the hips will result in opening the legs less to get a bigger stride, saving energy. 2nd is the RX, where every time the body drops and raises in height at Extreme poses, it will also drag forward and backwards

Notice most of the above happens because locomotion in a human body is very efficient, and those movement actually saves a lot of energy.

Finish Up

Lastly its Splining and adding more in-betweens to create the kick-off for the rear feet. And also adding in some drag for the toes. 

The most tricky part is finding out when to start tipping the toes and also when to lift foot from ground. Studying reference videos will greatly help!

Below is Ghosting for the curves to track the motion.