How a Biped Walks

If you don’t use Biped to create a walk for you, it helps to know that a human walk cycle is defined by two steps: left foot to right foot, followed by right foot to left foot (or vice versa). The two steps break down into four states:

1. Contact: Both feet are on the ground. At this point, the stride is at its longest: this is known as an extreme pose.
2. Down or “Recoil”: After contact, the weight goes down on the front leg. The body lowers, and both legs bend.
3. Passing or “Breakdown”: The front leg straightens and the back leg passes it. The body raises to a point that is higher than in the contact position.
4. Up or “High Point”: The back foot is now the front one, and is about to make contact. The other foot pushes up and forward, raising the body to its highest position.
5. Contact: The same as pose 1, but with the opposite leg forward.

You can start animating the cycle at any of these poses. Animators often prefer to begin with the contact pose, as that pose (in general, any extreme pose) is a good reference to build from.

You have to decide how many frames the walk cycle will use. Twelve frames yield two steps per second: this is a natural pace, which we will use in this tutorial. Cartoonists sometimes use an 8-frame cycle to create a fast, humorous walk. A 24-frame cycle would give (for film) one step per second, suitable for a slow-moving character. This tutorial uses a slightly slower 37 frames for the cycle.

Preparation for This Tutorial

• If you have not already downloaded the tutorial files (MAX scenes and other assets), download them now and unzip them into a project folder called \Autodesk 3ds Max 2011 tutorials. See Where to Find Tutorial Files.
• On the Quick Access toolbar, click (Project Folder) and set your current project to Autodesk 3ds Max 2011 Tutorials.