Although the walk cycle is now complete, you can make the biped’s motion more realistic by adding secondary motion such as swinging the arms, as this lesson shows. This lesson also shows a way to correct biped motion by examining the biped’s trajectory.

Set up the scene:

• Continue from the previous lesson.

Display trajectories:

Biped has its own trajectory display. You can use it to observe the movement of the center of mass in the walk cycle. You can also edit the keys on the trajectory directly in the viewport.

1. On the Track selection rollout, click (Body Horizontal).
2. On the Key Info rollout, turn on Trajectories.

   A line appears on the viewports showing the COM's trajectory: the path it moves along during the animation.

   WarningDon’t use the standard Trajectories functionality (the button near the top of the Motion panel) with Biped. Use the Trajectories button on the Biped rollout Modes And Display expansion bar Display group or on the Key Info rollout.
3. Scrub the time slider, and watch the biped center of mass moving along its trajectory.
4. On the main toolbar, turn on (Select And Move) toolbar. At the top of the Motion panel, turn on Sub-Object, and then click any key on the trajectory.

   

5. Use the Move Transform gizmo to move the keys to correct the trajectory.

   

   Edit keys in biped trajectory.

6. Turn off Sub-Object and Key Info rollout (Trajectories).

Add arm swings:

The character is starting to look like it’s walking, but it’s still quite stiff. Adding arm swings will put some life in the animation.

The arms swing opposite to the legs. When the right leg is forward, the left arm is forward. Arms bend at the elbow on the forward swing, and stretch out straight on the backward swing.

1. Scrub the time slider to decide where to place the arm swings.

   The right leg stretches out at frame 27, and you’ll keyframe the left arm to swing there.

2. Turn on (Auto Key).
3. At frame 0, move the left hand slightly, to set a key.
4. At frame 0, move the right hand slightly, to set a key.
5. At frame 27, move the left hand so it swings forward.

   Position the arm so there is a slight bend at the elbow. Since Auto Key is on, you have keyframed the arm by moving it.

6. On the Track Selection rollout, click (Opposite).

   The right hand is selected.

7. Move the right hand back slightly, so the arm is stretched out.

   Now the left arm is forward and bent a little, while the right arm is back and straight.

   

8. In the Front viewport, double-click Bip01 R UpperArm.

   The entire right arm is selected.

   

9. On the Motion panel, open the Copy/Paste rollout and click (Copy Posture).
10. Click (Create Collection). Name the Collection walkcycle1.
11. Turn on Create Snapshot From Viewport, just above the Paste Options group.

    

12. Click (Copy Posture). Name the Copied Posture RArm back.
13. At frame 37, click (Paste Posture Opposite).

    The left arm swings behind the biped.

14. At frame 27, double-click Bip01 L UpperArm.

    The entire left arm is selected.

15. On the Copy/Paste rollout, activate the Perspective viewport and click (Copy Posture) again. Name the posture LArm forward.

    

16. At frame 37, click (Paste Posture Opposite).

    The right arm swings in front of the body.

17. Turn off (Auto Key).
18. Scrub the time slider back and forth to evaluate the animation.

Add sway to the shoulders and hips:

You’ve animated the character by moving its hands and feet and center of mass. But the spine, hips, and head are still stationary. You’ll add some rotations to the shoulders and hips to complete the walk cycle.

1. Select Bip01 Pelvis and drag the time slider to frame 15.

   The left foot is locked at this frame with a planted key.

   Be careful where you add the hip rotations. Don’t inadvertently disturb the work you’ve done on the feet so far.

   As the legs extend and swing forward, the hips rotate slightly in the direction of the movement.

2. Rotate the pelvis about the Y-axis approximately –2 degrees, and set a key.

   The pelvis will not accept too much rotation. When you set the key, the pelvis corrects itself to account for the locked foot.

   

   Rotation added to the hips from the Front view.

3. Drag the time slider back to frame 0. Rotate the pelvis back 2 degrees about the Y axis, and set a key.
4. Rotate the pelvis back about –3 degrees about the X axis, and set a key.

   

5. Drag the time slider to frame 32. Rotate the pelvis about 4 degrees around the Y axis, then set a key. Repeat for the X axis, and set another key
6. Go to frame 39 and rotate the pelvis –2 degrees around the Y axis again, then set a key.

   The procedure is the same for the spine. At frame 27, the arms swing out in one direction. At frame 37, they swing in the opposite direction.

7. Select the biped spine object, Bip01 Spine.
8. At frame 27, rotate the spine in the direction of the arm swing (about –6 degrees around the X axis), then set a key.
9. At frame 37, rotate the spine approximately 12 degrees about the X axis, and set a key.

   The spine can freely rotate about all three axes. You can make adjustments on each one. Rotate about the Z axis for a more stooped walk. Increase rotation about the X axis to make the walk loose and floppy.

   Note Instead of animating the spine, you can animate the clavicles to raise or lower the shoulders.

Twist links mode:

The Bend Links rollout includes tools you can use for animation. You can use either the Bend Links or the Twist Links to animate the bending and/or twisting of the spine.

1. Turn on (Figure Mode).

   In the Structure Rollout, change Spine Links to 5.

   You can have up to 10 spine links, but five is enough to observe the Twist Links effect.

2. Turn off (Figure Mode).
3. Turn on (Auto Key).
4. On the Bend Links rollout, turn on Twist Links Mode.

   

5. Select the Bip01 Spine object. This is the lowest spine object in the biped.
6. Go to frame 0, and rotate the object slightly about the X axis to add a key. Do the same about the Y axis.
7. Drag the time slider to frame 27, and rotate approximately 10 degrees about the X axis so the spine rotates following the swing of the arms. The blue arm is swinging forward, so rotate the spine to match.
8. You can also rotate –1 degree about the Y axis.

   The slight rotation of the first spine object results in a larger effect further up the hierarchy.

9. At frame 37, repeat the rotations but in the opposite direction, in order to match the swinging of the green arm outward.

Save your work:

• Save the scene as walkcycle_fullmotion.max.