Polish the Walk Cycle

Set up the scene:

Continue from the previous lesson, or navigate to the \character_animation\quadruped folder, and open quadruped_walk_4.max.

Collapse the layers:

Select any part of the quadruped, then go to the Motion panel.
On the Layers rollout, click (Collapse).
Now the scene contains only a single layer of Biped animation: the keys you created on the Center of Mass & Spine layer are transferred to the main timeline.

Smooth out the trajectories:

Click and Ctrl+click to select all four of the quadruped’s feet.
On the main toolbar click (Curve Editor (Open)).
If you need to, pan the Controller window until you can see the tracks for all four feet. Expand the hierarchy if you need to, and Ctrl+click to select all four Transform tracks.
On the Track View status bar, turn on (Filter - Selected Tracks Toggle).
This simplifies the Controller window display by showing only selected tracks.
Make sure you can see all keys in the Function Curves window.
TipYou might have to click (Zoom Horizontal Extents) and (Zoom Value Extents) (on the Track View status bar) to see all the keys.
Drag a selection box to select all the keys in the animation.
On the Track View toolbar (the Key Tangents toolbar), click (Set Tangents To Smooth).
Smooth tangents give the animation a more organic feel, making it less abrupt.
Close Track View.

Trajectories of the dog’s right forefoot and knee before smoothing

Trajectories of the dog’s right forefoot and knee after smoothing
Play the animation.
The dog’s walk is now much smoother, and feels more “integrated”: more a single movement, and less a collection of individual movements.

Give the shoulder blades more freedom:

Turn on (Auto Key). Go to frame 1, select the dog’s shoulder blade (Biped01 R Clavicle), then rotate it up about 35 degrees in the local Z axis.
Make sure only the shoulder blade/clavicle is selected, then on the Copy/Paste rollout, click (Copy Posture).
Click (Paste Posture) to paste the shoulder blade posture at frame 13.
At frame 25, don’t paste the posture, but rotate the shoulder blade up about 30 degrees.
Pasting the pose lifts the dog’s foot off the ground, and we don’t want that to happen.
Click (Paste Posture Opposite) to paste shoulder blade posture onto the left shoulder blade at frames 1, 13, and 25.
Switch to display all four viewports before you preview the animation.
We have been working mostly in the Left viewport, but this is a three-dimensional animation, and it helps to look at the motion from other points of view.

With more movement in the shoulder blades, the quadruped walk has more of a loping feel to it: a gait that we associate with wolves and larger dogs.

Add some side-to-side movement to the pelvis:

Maximize the Top viewport.
Make sure (Auto Key) is on.
On the main toolbar, turn on (Angle Snap Toggle). Then at frame 1, rotate the pelvis to the dog’s right, 15 degrees in the local Y axis.
Go to frame 13. Rotate the pelvis to the dog’s left: –30 degrees in the local Y axis.
Finally, go to Frame 25, and restore the pelvis back to its frame 1 position: 30 in the local Y axis.
You can preview the animation, but the pelvis movement is really a basis for the spine movement, which you will add next.

Add side-to-side movement to the spine:

Make sure (Auto Key) and (Angle Snap Toggle) are both on.
Activate the Top viewport, if it isn’t active already.
At frame 1, select the lowest link of the spine, Bip01 Spine.
Rotate Bip01 Spine to the dog’s right, 15 degrees in the local Y axis.

Notice that Biped maintains the head facing forward, which is what you want it to do.
Also at frame 1, rotate Bip01 Spine02 –10 degrees in the local Y axis, and then rotate Bip01 Spine03 (the shoulders) –15 degrees in the local Y axis.

The spine describes an S-curve as the dog walks, with the shoulders rotating in the opposite direction from the hips.

WarningDon’t use Page Up or Page Down to select spine links. This select other biped parts as well, such as arm and leg links, and will generate unwanted animation.
Go to frame 13. Rotate the three spine links in the opposite direction: –15 degrees in the local Y axis for Bip01 Spine; 10 degrees for Bip01 Spine02; and 15 degrees for the shoulders, Bip01 Spine03.

Because of other Biped keys, the spine returns to a straight posture by frame 5, so you don’t have to “overcompensate” the rotation value as you did for the hips.
Finally, go to frame 25 and rotate the spine to its frame 1 position: 15 degrees in the local Y axis for Bip01 Spine; –10 degrees for Bip01 Spine02; and –15 degrees for the shoulders, Bip01 Spine03

The last bit of movement to add is, appropriately, the tail, which mirrors the spine movement in a similar S-curve. Like head movement, tail movement is a secondary motion that doesn’t affect the mechanics of the walk, but does give it greater realism.

Add side-to-side movement to the tail:

Make sure (Auto Key) and (Angle Snap Toggle) are both on.
Activate the Top viewport, if it isn’t active already.
At frame 1, select the lowest link of the tail, Bip01 Tail.
Rotate Bip01 Tail to the dog’s left, –15 degrees in the local Y axis.
Rotate the remaining three tail links in the opposite direction, to counter the side-to-side motion of the spine.
Go to frame 13 and as you did for the spine, rotate the tail links to mirror the frame 1 pose.
Go to frame 25 and restore the tail to its frame 1 pose.
Tip To save time, you can select all the tail links, copy their posture at frame 1, and paste the posture at frame 25.
Turn off (Auto Key).

Correct the intersecting feet:

The last bit of “polish” to add to the dog’s walk is to remove the intersecting feet that was a result of simple footstep blocking.

Click (Maximize Viewport Toggle) so you can see all four viewports.
Drag the time slider to frame 10. At this point, the right forefoot intersects the right hind foot.
In the Left viewport, move the foot up and out of the way of the hind foot, and then click (Set Sliding Key).

Now the forefoot lifts out of the way before the hind foot steps down. Scrub the time slider to make sure you’ve corrected the intersection: the forefoot should lift from the ground just before the hind foot descends.
Drag the time slider to frame 22.
Here there is the same problem with the left feet intersecting.
As you did for the right forefoot, move the left forefoot up and away from the descending hind foot, and then click (Set Sliding Key).
Now neither the right nor left feet intersect during the walk.

Preview your work:

Now you’ve finished animating the dog’s walk. Switch to all four viewports, and play the animation. Stop playback when you’re done.

Save your work:

Save the file as my_quadruped_completedwalk.max.
To see a completed version of the animation, open quadruped_walk_completed.max.

Summary

In essence, a quadruped walk cycle combines two biped walk cycles. This tutorial demonstrated the ForeFeet toggle that enables hands to behave as feet, with sliding keys on the ground plane. It also showed one way to smooth tangents for a better-integrated animation.

Notes on Looping and Reloading Biped Animation

To loop the quadruped walk (or other Biped animation), 3ds Max doesn’t allow you to use Parameter Curve Out-Of-Range Types, but you can use the Motion Mixer to loop a walk cycle.

Also, when you have rotated the COM as you did for the quadruped, if you save the motion as a BIP file you should save a FIG file as well as a BIP file. Then the method to use depends on how you are loading the BIP file:

If you load the BIP file motion onto a new Biped, then after you click (Load File) on the Motion panel, in the Open dialog, turn on Restructure Biped To Match File.
If you use the Motion Mixer to add the BIP file to the animation, then first go into Figure Mode and load the FIG file onto your Biped.
The FIG file saves the COM rotation data, so you need to load it before loading the BIP animation: Otherwise, the orientation of the motion will not match the rest of the scene.