Redirecting the motion within a clip

Learning Resources > Tutorials > Getting Started with Maya > Animation > Lesson 4: Nonlinear animation with Trax >

Motion capture data can be used in a variety of ways. You can redirect the motion of a character using the same motion capture data. The Redirect tool allows you to alter the original animation for a character by modifying its path or orientation at any time during its animation. The Redirect tool does this by offsetting the translation and rotation attributes for the selected character.

For example, you can change the start or end point of a character’s animation by redirecting the character’s starting position or by redirecting its motion during the animation. You can redirect a character in an existing animation sequence in the scene or a character associated with a clip within the Trax Editor.

In the steps that follow, you redirect the skeleton to turn to the right while walking. The workflow for the redirection is as follows:

Scrub forward in the animation to determine a location in the clip where you want the character to turn. A realistic choice is where the ball of the skeleton’s right foot is planted on the ground plane because this accurately simulates how a real person might turn.
Select the entire skeleton. In this example, selecting the entire skeleton selects it at the root joint (the top node of the skeleton’s hierarchy) Selecting at the root joint ensures that the entire skeleton gets redirected when the redirection control is applied.
Create and position a rotation redirection control using the Redirect tool.
Keyframe an initial starting rotation for the redirection control.
Rotate the redirection control so the skeleton faces the new direction of travel.
Keyframe the second rotation for the redirection control.

To create a redirection control for the skeleton

In the Time Slider, drag the current time indicator to frame 36.
This frame is where the ball of the skeleton’s right foot is planted on the ground plane. Use this frame as the location where the skeleton will turn to the right.
Select the skeleton in the scene view by click-dragging a bounding box around it.
In the main menu, select Character > Redirect > .
In the Character Redirection Options Window set the Redirection Type to Rotation only and then click the Redirect button.

A Rotation redirection control appears between the hips of the skeleton, where the root joint for the skeleton’s hierarchy is.

You want the skeleton to pivot (rotate) while standing on the ball of its right foot. To do this, you need to move the redirection control to the ball of the right foot of the skeleton.

To move the redirection control to the ball of the foot

From the Toolbox, select the Move tool.
The Move tool manipulator appears on the redirect manipulator.
Press the v key and click-drag the redirection control until it is located on the ball of the right foot as shown below.
Pressing the v key while using the Move Tool momentarily enables the Snap to Points tool.

The redirection control is now positioned to redirect the skeleton’s walking motion. To complete the redirection process, you need to set keyframes while setting the redirection control so the redirection of the skeleton can occur.

To keyframe the redirection control

With the redirection control selected, press s to set a keyframe.
A red tick appears in the Time Slider at frame 36 indicating the keyframe. Setting a keyframe establishes the starting rotation for the redirection rotation of the skeleton.
In the Time Slider, drag the current time indicator to frame 57.
The skeleton updates to a position where its left foot is planted on the ground plane. This is the location where you want the skeleton to be rotated to its new direction of travel.
In the Channel Box, with the redirection control still selected, set the Rotate Y attribute to -45.
Rotate the redirection control approximately -45 degrees about the Y axis until the skeleton is facing in the direction shown below. (You can use the Channel Box values as a guide.)
With the redirection control still selected, press s to set a keyframe.
Setting a second keyframe establishes when the redirection rotation for the skeleton ends.
Set the current time indicator to frame 1.
Click anywhere in the perspective view to deselect any items in the scene.
Click play on the Time Slider playback controls to play back the clip.
The skeleton takes two steps and then turns to its right after it reaches the redirection control, and continues walking in the new direction of travel and stops when it completes its walk cycle.
Press stop on the playback controls to stop the playback and reset the current time indicator to frame 1.
NoteWhen redirecting motion within Trax, you may want to consider creating a clip that contains the redirection animation to make it possible to reposition the redirect animation as a clip.

Now that you’ve redirected the character to a different direction of travel during the walk cycle, you can reuse some of the motion from the original source clip you created earlier in the lesson and saved to the Outliner/Visor.

You insert the source clip from the clip Library in Trax. The clip Library keeps track of the source clips and poses for the current character set. When the source clip is inserted from the Library, a copy of the source clip is created in a new track.

Once you import the source clip and make a copy of it, you trim the duplicate clip to make the character stop walking and then sit in a different location than the original motion capture.

To insert the source clip

In the Trax Editor, select Library > Insert Clip. Choose WalkSitSource from the drop-down list.
A duplicate copy of the WalkSitSource clip is created, and inserted onto a new track.
In the Trax Editor, select View > Frame All.
The track view area updates to display all clips in their entirety.
In the Trax control area, click the Mute button for the track that contains the WalkCycle clip.

The muted track dims to indicate it is inactive. When the walk cycle track is muted, the character updates to appear in the Da Vinci pose at the origin based on the original source clip.
Drag the current time indicator to frame 98.
The skeleton updates in the view and the redirection that was applied also occurs. Remember that the redirection occurs for the character, and not the clip.
Click on the WalkSit clip in the track to select it.
In the Trax tool bar, click the Trim Clip Before Current Time icon to trim the section of the clip that occurs before frame 98.

The WalkSit clip is trimmed and the portion of the clip before frame 98 is discarded.
Click the Mute button again for the track containing the WalkCycle clip to reactivate the track.
The dimmed track becomes active again. The skeleton however has updated to an incorrect pose near its previous position. This occurs because the two active clips overlap, and the character is receiving conflicting positional information as a result. (That is, double translation and rotation information.)
Drag the WalkSit clip to the right in its track until its Frame In number matches the Frame Out for the WalkCycle clip.
The pose for the skeleton is updated to the correct position.
Reset the current time indicator to frame 1.
Click play on the Time Slider playback controls to play back the animation.
The skeleton takes two steps and then turns to its right after it reaches the redirection control, and continues walking in the new direction of travel, stops, and then sits.
Press stop on the playback controls to stop the playback and reset the current time indicator to frame 1.

A small jump cut occurs during the transition between the two clips. The jump cut occurs because the poses for the skeleton do not match from the end of the first clip and the beginning of the second. In your own work, try to anticipate how motion will blend between clips when working in Trax. You can correct the jump cut in this particular example by extending the WalkCycle clip.

To extend the WalkCycle clip to correct the jump cut

In the Trax Editor, double-click on the WalkCycle clip in the C2 region.
The number becomes highlighted indicating you can edit the number.
Type 2.2 to edit the clip so it cycles 2.2 times.
The new Frame Out number for the WalkCycle clip becomes 126. It now overlaps in time with the WalkSit clip.
Drag the WalkSit clip to the right until its Frame In number becomes 126.
Click play on the Time Slider’s playback control to play back the animation.
The jump cut is less noticeable than before.
Press stop on the Time Slider’s playback control.
You have completed this lesson. Before leaving this lesson, reset the joint size back to its default setting.

To reset the joint size

From the main menu, select Display > Animation.
The Joint Display Scale window appears.
Set the Joint Display Scale to 1.
Close the Joint Display Scale window.