Keyframing an IK Skeleton Maya 2012

Transcription

1 Michael O'Rourke Keyframing an IK Skeleton Maya 2012 (This tutorial assumes you have done the Creating an Inverse Kinematic Skeleton tutorial in this set) Concepts Once you have built an Inverse Kinematic skeleton, you can keyframe the joints and handles to create animation There are many techniques for doing this (See the many tutorials in the Character Animation set for more details) Here we present the simplest of those techniques -- basic keyframe setting Retrieve an IK Skeleton Retrieve your skeleton from the Creating an Inverse Kinematic Skeleton tutorial in this set Or make a similar skeleton with IK Handles at the ankles and wrists Keyframe the Ankle s Handle Moving an IK handle cause the joints it controls to bend So you animate those joints By keyframing their IK handle

2 Select the IK Handle for one of the ankles >Animate >Set Key [] >Edit >Reset Settings >Set Key All the handle s parameters in the Channel Box are highlighted, indicting that they are keyframed Translate the ankle s IK handle straight up The knee bends Hit the s key to keyframe it Scrub through the timeline to see the animation so far Hit the t key to show the manipulator icon for the IK handle Click-drag the blue circle icon to rotate the leg at the hip This controls a Twist parameter Notice the Twist value changing in the Channel Box Hit the s key to keyframe the handle s parameters at that frame Scrub through the timeline to see the animation The knee bends The ankle rise up The leg rotates at the hip Keyframe some positions for the other ankle s IK handle Keyframe the Arms Handles Select the IK Handles at each of the wrists

3 Hit the s key to keyframe their starting values Create several keyframes for the wrists handles, as described above for the ankle Forward Kinematics on Other Joints If a joint is not controlled by an IK handle, you can keyframe it with normal forward kinematics For example, in our model: the spine joints and the head joint are not controlled by an IK handle Select the head joint Hit the e key to go into rotation mode Hit the shift-e (Upper-case E) key combination to save keyframe information for the three rotation parameters In the Channel Box, the three rotation values should be highlighted Rotate the head joint Hit the shift-e key combination to save a rotation keyframe Try the same approach for some of the spine joints You may have to rotate several of them to get a smooth bend in the spine Test Translate the Pelvis Select the pelvis joint

4 --that is, the topmost parent joint of the entire skeleton Translate it straight down in Y Notice that the ankle Handles stay in place Pulling the pelvis down causes the knees to bend When you translate the topmost parent node (pelvis, in our model), any IK Handles that are keyframed remain in place This is good it keeps the feet on the floor Any IK Handles that are not yet keyframed will move with the pelvis Translate the pelvis forward a lot The ankle Handles remain in place causing the legs to stretch out Undo your pelvis translations so it is back to its original position Keyframe the Pelvis Select the pelvis joint Hit the s key to keyframe all the parameters for the pelvis joint Select all the IK handles (two wrist + two ankle) Hit the s key to keyframe all their parameters Translate the pelvis forward Since the whole body has translated forward, you also need to translate the other handles forward as well Translate the two ankle handles forward into a walking position Translate the two wrist handles so the arms are swinging Rotate the limbs with the Twist parameter, if necessary Select all of the IK handles (two wrist + two ankle) Hit the s key to save all their parameters

5 (You can also simplify this keyframing operation, by turning on the Automatic Key button the little Key with a Plus sign, top menu When Automatic Keying is on, Every time you move an object, it is automatically keyed in that position) To make your character move/walk, you will: Keyframe the pelvis (top) joint Keyframe the IK handles Rotate the limbs with the Twist parameter Rotate other joints with forward-kinematic keyframing There are many other techniques for doing this as well They can be easier to use But harder to learn See the many tutorials in the Character Animation set for more details Adjust Timing You can use all the normal techniques for fine-tuning your animation For example, the Dope Sheet the Graph Editor Straight-Ahead Animation When you position and keyframe your model one keyframe after another, in sequence as described above, This is called straight-ahead animation Compare and contrast this with pose-to-pose animation, as described in the tutorials on Poses in this set