Track View

Main Toolbar > Track View

In this Track View of a running motion, footsteps are represented by colored squares, footstep numbers appear inside the squares, the other numbers represent foot-air duration. Red keys in this image show the center of mass vertical and horizontal tracks. Red keys are associated with the center of mass and only appear at touch down keys from an airborne period, or lift keys just before an airborne period. Red keys can only be moved in time by moving the associated footstep.

Biped and Track View

Track View provides a way to create and adjust biped keyframes, edit biped footsteps, and specify a freeform period. Biped keys display in a familiar "dots on a track." Footsteps display as squares that can be moved in time. Biped dynamics and footsteps work together; if footsteps are moved in time, Biped adapts leg keys and vertical positions to account for the editing. There are a couple of restrictions, you can't overlap footsteps on the same track, or move footsteps into negative time.

Tip: Select a biped object and click Zoom Selected at the bottom left corner of the Track View dialog to place the selected biped object at the top of the Track View Hierarchy window. This is a quick way to locate a biped object in Track View.

Footsteps in Track View

By default, left leg footsteps are blue and right leg footsteps are green. Inactive footsteps are more saturated values of blue and green, active footsteps are pale blue and green. The left edge of each footstep block indicates when a foot touches a footstep (Touch State). The right edge of each footstep block indicates the last frame the foot is on a footstep (Lift State). The space between two footsteps indicates an airborne state for the foot (Move State). The period between the Touch and Lift States is the Plant State.

Separate Tracks

By default, Biped stores all of the toe, foot, and calf keys in the thigh track. The finger, hand, forearms, and upper-arm keys are stored in the clavicle track. All the spine keys are stored in the spine 01 track. Although you can see all of these objects in the Track View hierarchy, they have no transform track, unless you enable them in the Separate Tracks group of the Animation Properties rollout.

For example, if you rotate a biped foot, a key is created in the biped thigh track. This optimized approach works well in many cases. If your animation requires extensive hand and finger keyframing, turn on Arms on the Animation Properties rollout, all of the arm transform tracks are now enabled, down to the first finger link on each finger. Now if you delete an upper arm key, your finger-hand animation is preserved.

Editing Biped Keys in Track View

Track View is often used to change multiple keys simultaneously. For example, to change Dynamics Blend for all the vertical center of mass keys, select all the vertical keys in the Track View window, display the TCB (Tension, Continuity, and Bias) dialog by right-clicking over the selected keys and change the Dynamics Blend parameter.

Right-click a key in Track View to display the TCB dialog

Edit Keys

If Edit Keys is enabled on the Track View toolbar, the following functions are possible:

Edit Time

If Edit Time is enabled on the Track View toolbar, the following functions are possible:

Set Multiple Keys

Use Set Multiple Keys on the Keyframing rollout to automatically select keys for your animation (all of the leg keys in a move state (airborne), for example). This works well with Track View open, all the keys selected by the state filters in the Set Multiple Keys dialog display as white keys in Track View. Use Apply Increment in the Set Multiple Keys dialog after adjusting a biped limb to change the selected keys.

How Dynamics and Footsteps Relate

When footsteps are created, a footstep track displays in Track View. Footsteps appear as blue and green blocks, laid out to show their exact placement in time. If you examine the center of mass tracks with footsteps, you will notice that frames where leading and trailing edges of the footsteps occur also have keys for the center of mass Body Vertical and Horizontal tracks. These keys contain dynamics information used by character studio to calculate airborne body position relative to gravity, and leg bend on landing and balance. Biped Dynamics is the reason you do not need a vertical center of mass key at the top of a jumping motion or at the bottom of dip when the biped lands from an airborne period.

Click and drag the middle of a footstep to move it in time. Click and drag one edge of a footstep to stretch the footstep in time.

Note: Changing the duration of footsteps or moving them relative to one another may change the 'support relationships' of the footsteps. Whenever the support relationships change, Biped generates new keys and deletes any existing leg keys in the airborne period between the edited footsteps.

Because of Biped Dynamics, no keys are necessary for the highest part of this jumping motion or for the dip when the biped lands; character studio calculates the trajectory of the Body. This image shows the center of mass trajectory. Keyframes are white squares on the trajectory.

Simply change gravity (GravAccel on the Animation Properties rollout), and the jumping motion is flattened. The biped looks like it's hopping on the moon.

By selecting half the footsteps in Track View and moving them to the right in time, the biped has to jump higher to account for the added time to the next footstep. Notice the yellow dots, representing frames, are tightly bunched together; there are more frames in this airborne period.

Here, the center of mass is moved in the Z plane. Now the biped heel never hits the ground; the biped appears to do a little jump using just his toes. Here, character studio understands that you want to override the calculated trajectory and position the keyframe yourself.

Freeform Animation

It is left to you to create all the keys in a freeform animation; Biped Dynamics is not active and does not recalculate body position. Balance Factor is active in a freeform animation. A completely freeform animation contains no footsteps.

To start an entirely freeform animation, simply create a biped and begin keyframing. A dialog warns that you are starting a freeform animation, and the Footsteps Mode button on the General rollout grays out, indicating that you cannot create footsteps.

You will often want a freeform period in a footstep sequence; for a walk then fall type of motion for example. In cases like this, a freeform period is specified between footsteps in Track View using the Footstep Mode dialog. A combination of footsteps and freeform is often required when motion capture data is imported. A freeform period is created using controls in the Footstep Mode dialog and display as a yellow boxes between footsteps in Track View.

Right-click the footstep track to display the Footstep Mode dialog; here you specify a freeform period, select multiple footstep edges, and set footstep numbering display options.


To copy keys in the left arm track to the right arm track

  1. Click Edit Time on the Track View toolbar.

  2. Click the left Clavicle Transform track in the Track View Hierarchy window.

  3. Click and drag on the Clavicle track to select time in the Track View Edit window.

  4. Click Copy Time on the Track View toolbar.

  5. Select the right clavicle transform track.

  6. Click Paste Time. A dialog gives you a choice between an Absolute and Relative paste. An Absolute paste will paste over the same frames; a relative paste will paste starting where you clicked in the track before using the Paste Time command.

    Note: Keys cannot exist past the end of footsteps. Copy and paste a shorter period of time if a warning displays.

To select a footstep

To select multiple footsteps, do one of the following

To move footsteps in the time

To change vertical dynamics (gravity) for multiple center of mass (COM) keys in Track View

  1. Open Track View and select all the vertical COM keys (or any combination that you want to change).

  2. Right-click over one of the selected keys to display the TCB dialog.

    Change the value of Dynamics Blend in the TCB dialog. This changes it for all selected keys.

    Note: This will only affect the biped during airborne periods in a footstep animation. Changing Dynamics Blend for all center of mass keys in a walk motion will not affect the walking motion.

To change the duration of a footstep

  1. Click the left or right edge of a footstep.

    In addition to a white border, a small white key appears to indicate the border is adjustable.

  2. Drag to make the footstep longer or shorter.

    You can adjust a selection of multiple footsteps this way.

To clone biped keys in Track View