Understanding Biped

The Biped

The biped skeleton created with the Biped module is a two-legged figure created as a linked hierarchy, and designed for animation. The biped skeleton has special properties that make it instantly ready to animate.

Figure and Keyframe Modes

character studio is designed to interchange motion and characters. In Figure mode, you pose the biped to fit your character model. In Keyframe mode, you animate the skeleton. Motions created for the biped can be saved and loaded onto other biped skeletons with different physical characteristics. For example, you could animate a giant ogre, save the animation, and load it onto a small child. Motion files are saved in the proprietary BIP format.

You can use these files in a variety of ways with Motion Flow, the Motion Mixer, and the Crowd tools to combine animation or animate multiple characters.

Animating the Biped

The two primary methods used in creating biped animation are footsteps method and freeform method. Each has its advantages. You can convert animation between the two methods, or you can combine both in a single animation. For detailed information, see these sections: Footstep Animation and Freeform Animation.

Biped Properties

The biped skeleton has these properties, designed to help you animate faster and more accurately:

• A human structure—Joints on the biped are hinged to follow human anatomy. By default, the biped resembles a human skeleton and has a stable inverse-kinematics hierarchy. This property means that when you move a hand or foot, the corresponding elbow or knee orients itself accordingly, and produces a natural human posture.
• Customizable for non-human structures—The biped skeleton can easily be made to work with a four-legged creature or an animal that naturally leans forward, such as a dinosaur.
• Natural rotations—When you rotate the biped spine, the arms maintain their relative angle to the ground, rather than behaving as though fused to the shoulders. For example, take a biped in a standing position, with arms hanging at its sides. If you rotate the spine forward, the fingers touch the ground rather than pointing behind it. This position is more natural for the hands, which speeds the process of keyframing the biped.

  This feature also applies to the biped head: When you rotate the spine forward, the head maintains a forward-looking orientation.

• Designed for footsteps—The biped skeleton is specially designed to animate with character studio footsteps, which help solve the common animation problem of locking the feet to the ground. Footstep animation also provides an easy way to rough out animation quickly. For more information, see Footstep Animation.