Creating a Full Body IK Skeleton
Creating a skeleton that moves more or less as a bipedal human character has become much easier with the advent of the Rig Maya Guide" href="/guide-3/hands-on-working-with-a-full-body-ik-animation-rig.html">Full Body IK system. The Full Body IK system is a direct outgrowth of the MotionBuilder system now being integrated into Maya as a first-class plug-in rather than being a stand-alone program as it was previously (one can, of course, still purchase MotionBuilder as a separate application from Autodesk). Full Body IK is a paradigm shift for those who have rigged characters in Maya before: the FBIK system depends on a new, multi-node effector called the human IK Effector, or hikEffector. Whereas all other effectors/IK handles only allow one input to them, the hikEffector places all control elements (feet, hands, and so on) within one node. What this new data scheme allows is automated reaction of body elements as a character is manipulated in the scene window. For example, as a character's hips are moved up and down, the Full Body IK system will cause the spine, arms, and legs to react appropriately, which not only creates realistic secondary animation, it also eases the job of animators.
Full Body IK can also create quadruped rigs, as well as "nonstandard" human rigs (with extra fingers or toes, for example). Although we will concentrate on creating a standard bipedal rig, Maya's documentation explains how to create these other types of rigs, and you can create a sample quadruped (or biped) rig by selecting Skeleton ■ Full Body IK ■ Get FBIK Example. Included are a camel and a man.
Figure 8.26 Adding Full Body IK to Machismo's skeleton
Creating Full Body IK is simple once joints have been named or labeled properly, though you will usually have to take several steps after creating the Full Body IK system to get the desired behavior from the system. To create the Full Body IK system, select the root joint of the skeleton, and then, under the Animation menu set, choose Skeleton ■ Full Body IK ■ Add Full Body IK □. In the option box, set Identify Joints to By Name and leave Posture set to Biped. Click Add, and in a few seconds you should see a rigged skeleton, as shown in Figure 8.26.
Once your Fully Body IK system has been created, try playing around with the effectors: grab any of the boxes or large circles on the skeleton (at the hands, feet, neck, head, and so forth) and move them around. The character's body should react more or less in a natural motion. Note that whenever a Full Body IK effector is selected, all joints that are affected by it turn magenta. (Thus, when the HipsEff is selected, the entire skeleton turns magenta.) For reference, you can open the MachismoFBIKStart.ma file on the CD.
Figure 8.26 Adding Full Body IK to Machismo's skeleton
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