For a more realistic walk, the quadruped’s hips and shoulders need to move up and down as the weight of the animal shifts from leg to leg. You will create a layer that contains this animation. Using a new layer allows you to compare the original animation with the newly created keys. When you are satisfied with the new animation, you can collapse layers to integrate the old and new animation.

Set up the scene:

• Continue from the previous lesson, or navigate to the \character_animation\quadruped folder, and open quadruped_walk_3.max.

Create a layer for the hip and shoulder motion:

1. Select any part of the quadruped, go to the Motion panel, and open the Layers rollout.
2. On the Layers rollout, click (Create Layer). Name the new layer Center of Mass & Spine.

   

3. Also on the Layers rollout, in the Retargeting group, turn on the retargeting buttons for all four legs. Turn on IK Only as well.

   

   These controls preserve the IK constraints from the animation on the base layer. Without them, moving the quadruped’s center of mass (COM) would simply translate the entire quadruped, disregarding the sliding keys you created earlier to control the feet.

4. Click Update.

   If you select a foot, you can see that the sliding keys now appear in the Track Bar for this layer.

Create movement for the hips:

1. On the Motion panel, open the Track Selection rollout. Click (Body Vertical) to turn it on. This selects the COM, as well.

   Because the quadruped is walking in place, you need to adjust only the vertical position of the COM.

2. Go to frame 1. Turn on (Auto Key), then move the COM down slightly (frame 1, as you might recall, is a Down pose).
   NoteWhen you work with layers, the viewport feedback isn’t fully interactive: as you move the COM, the feet descend below the ground plane. After you release the mouse, 3ds Max recalculates IK and the feet snap into the position where they should be.

   

   Lowered COM for the Down pose

   As you animate on the Center of Mass & Spine layer, viewports show the original animation as a red stick figure with a box for a head.

3. On the Track Bar Shift+drag the new COM key to make a copy of it at frame 13 and frame 25, the other two Down frames in this cycle.
4. Go to frame 7, the Up state, and move the COM to a point that is higher than the original animation.

   

   Raised COM for the Up pose

   ImportantWhen you raise the COM, try to make sure that the limbs are not extended too far: if they are fully extended, then Biped tends to generate abrupt motion, which doesn’t look good or natural.
5. Shift+drag the new key from frame 7 to create a copy at frame 19.
6. Go to frame 10, the first Contact pose for the hind legs, and move the COM to a vertical position midway between its heights for the Down and Up poses.

   

7. Shift+drag the new key from frame 10 to create a copy at frame 22.

   If you scrub the time slider or play the animation, you can see that the hips now bob up and down in a more convincing version of a walk. The shoulders and spine still seem rigid.

Create movement for the shoulders:

1. Go to frame 1. Make sure (Auto Key) is still on.
2. Select the lowest spine link, Bip01 Spine, and rotate it up a bit (not too much).
3. Select the next spine link, Bip01 Spine 1, and rotate this link down a bit.

   The goal is to have the outline of the spine match the contour of the dog’s body in the reference sketch.

   

4. Shift+drag to copy the new key from frame 1 to frames 13 and 25.
5. Go to frame 7, the Contact pose for the forelegs, and repeat these adjustments to the lower two spine links. Again, you want to have the spine follow the dog’s body in the sketches. At Contact for the forelegs, the dog’s weight shifts from the pelvis to the shoulders.

   In this step, you might want to adjust the third spine link, Bip01 Spine 2, down a little bit, as well.

   After you adjust the spine, if the forefeet don’t appear to be reaching the ground plane properly, go to the Layers rollout Retargeting group, and click Update.

   

6. Shift+drag to copy the new key from frame 7 to frame 19.

   If you scrub the Time Slider, you can see that the spine already has a more fluid movement.

7. Go to frame 4, the Up pose for the forelegs. Again, rotate the spine links to follow the dog’s body. For this pose, the spine should be a bit higher than the pelvis.

   

8. Shift+drag to copy the new key from frame 4 to frame 16.

With the spine movement added, the quadruped looks less like a robot and more like an animal walking.

Add some head movement:

1. Go to frame 1, and select the head of the quadruped.
2. On the Key Info rollout, click (Set Key).

   This sets a key for the head and the upper neck link, Bip01 Neck1.

3. Shift+drag the new key from frame 1 and copy it to frame 25, then copy it to frame 11 as well.
4. Select the lower neck link, Bip01 Neck, then click (Set Key) to set a key for it as well.
5. Shift+drag the neck key to copy it to frames 11 and 25, as you did for the head.

   You’ve now set up a reference pose about which other head poses can move. Head movement is secondary motion. It’s called “secondary” because the walk doesn’t depend on it, and it doesn’t affect the leg or body motion. However, secondary motion can add a great deal of life to an animation.

6. Go to frame 7. Make sure (Auto Key) is on, then rotate the neck and head upward slightly.

   

   The idea is that in general, the dog looks where it is going when it’s forelegs are in the Contact position.

7. Shift+drag the new key to copy it to frame 19.
8. Go to frame 11. Rotate the neck links so they are roughly parallel to the ground, and then rotate the head so it is looking slightly down.

   

   As you probably noticed, frame 11 comes one frame after the Down pose at frame 10. Secondary motion tends to lag a little behind primary motion. Also, setting keys slightly out of phase in this way helps keep the animation from appearing too mechanical.

9. Shift+drag the new key to copy it to frame 22.

Save your work:

• Save the file as my_quadruped_legs_spine_head.max.