Understanding Footstep and Body Keys

When you activate footsteps, keys are created for biped body parts. Before you work with footstep placement and timing, it's essential that you understand the default keys generated and how they relate to footstep editing.

Leg States

A leg moving through a footstep has four states, beginning with the foot on the ground. Then the foot lifts, moves through the air, and returns to the ground again. These leg states are labeled by character studio to help you work with footsteps and leg/foot keys more easily when editing footsteps.

These states are referred to in these topics to aid in understanding more advanced footstep concepts, so it's important that you become familiar with them.

• Touch occurs at the leg keyframe where the foot first touches the footstep, and always corresponds with the start frame of a footstep in Track View. The Touch state is always one frame long.
• Plant occurs after touching, and before lifting. It is always in between the start and end frames of a footstep in Track View. The Plant state is usually more than one frame long.
• Lift occurs at the keyframe where the foot lifts off the ground, and always corresponds with the end frame of a footstep in Track View. The Lift state is always one frame long.
• Move occurs while the foot is in the air, and is always in the intervals between footsteps in Track View. In walking, while one foot moves, the body is supported by the other leg. In running or jumping, there are periods where the body is not supported and moves in midair.

For more information on these keys, see Editing Footstep Timing.

You can display the current state of each leg by turning on Leg States in Biped rollout Display group. The state name appears in viewports near the foot, corresponding to the state at the current frame.

Note: State names appear only on footsteps that have been previously activated. If active footsteps have been deactivated and edited, the state names that appear will correspond to states the legs were in before deactivation. For this reason, leg states displayed between deactivation and reactivation might not be accurate.

Regardless of the footstep pattern, activating footsteps will always cause leg keys to be generated at each lift and touch frame. Although you can alter these keys to some degree by going to a touch or lift keyframe, turning on Auto Key and changing the leg positions or rotations, you cannot delete these keys.

To change the foot/leg animation after footsteps are activated, see Animating Legs and Feet and Adjusting Body Keys in Track View.

Body Keys

When foosteps are activated, keys are also generated for the center of mass (COM) object, the blue tetrahedron at the center of the biped's pelvis. The position and rotation of the COM determines the horizontal and vertical position of the biped body, as well as its rotation.

Unlike other biped parts or 3ds Max objects, the COM has three separate animation tracks, two for motion and one for rotation. You select these tracks by clicking the appropriate button on the Track Selection rollout:

• Body Horizontal
• Body Vertical
• Body Rotation (displays keys for the Body Turning track)

Keys for these tracks are generated automatically when you activate footsteps. You can view the keys for each track on the Track Bar by turning off Footstep Mode and clicking the corresponding button listed above. These tracks are also visible in Track View's Dope Sheet mode.

Note: When you select the COM, only the keys corresponding to the selected track are displayed. If you select the COM and do not select a track, no keys are displayed on the Track Bar, even if the COM is animated. You can find out which COM track is selected by checking the status of the buttons displayed above. When a button is turned on, the track is selected.

You can animate the COM or change existing keys after footsteps are activated. To change COM keys after footsteps are activated, see Animating the Upper Body and Adjusting Body Keys in Track View.