Understanding Motion Builder’s IK/FK Control Rig Tutorial |
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By Ricardo Tobon Page 2 Synchronization When keying on Full Body mode and Body Part mode, Motion Builder keep the Control Rig synchronized for you. This means that FK and IK controllers move together so you can blend seamlessly between them.
Go to frame 24 rotate the controller 70 degrees on the local Y axis and key frame. Go to frame 24 rotate the controller 70 degrees on the local Y axis and key frame. When you play the animation you will see both arms go down at the same time (mov 1).
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Mov 1.
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Go to frame 24, select the Left Wrist Effector and the Right Wrist Effector; activate their Reach T and Reach R by setting them at a value of 100. You will see the Right Arm go back to the original T position while the Left Arm stays in place. When you play the animation the left arm still moves down but the right stays up (mov 2).
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Mov 2.
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By activating Reach T and the Reach R you are activating the IK controller. Since you keyframed the left arm in Body Part mode keys where placed in the FK components of the arm as well as the IK components keeping both controllers synchronized. In contrast, when you keyed the right arm in Selection mode you only keyed the selected bone so the IK components were never selected or moved causing the FK controllers and the IK controllers to become unsynchronized. Linear and Arched Trajectories Depending on which type of controllers are driving the rig (FK or IK) your character might move different between poses.
Since we have been keying on Body Part mode, every element of both arms has been key framed and the FK controllers as well as the IK controllers are synchronized.
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Mov 3.
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Of course the left arm which is driven by FK controllers moves more natural because it moves in an arc which is one of the basic principles of animation. Although when you are selecting elements in the Character Controls window you are basically posing your character through the use of IK controllers. But until you activate the Reach T and Reach R of a section, you will be driving its elements with the FK controllers.
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