6 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.7 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 Spine03The 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.1036 | Chapter 5 Character-Animation Tutorials