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Now to put together a FK-IK switcher for your arms. With this you can have your character place their
hands on a table (and stick) then easily have them pick it up and wave it around. Select your arm bone, while holding down Ctrl drag the arm back onto the shoulder bone. This will create a duplicate arm chain all ending with a 2. With the new duplicate arm bone selected, hit "R", hold Ctrl and slightly rotate the arm chain upwards. |
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You can delete the fingers from the duplicate chain, they're not necessary. Rename the new bones. I usually delete the extra '2' and add a 'FK_' to the front. |
 | Drag the FK_Arm chain onto the shoulder bone again, creating a 3rd set of bones. Rotate them down and rename them IK. |
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Ctrl-Drag the IK_Hand bone onto the CoG. (or root or whatever you named your parent bone) Adjust the length of this copied bone so it sticks out farther, rename it to HandTarget. Hide the bone for now, it may get in the way. |
 | Create a new percentage pose slider. |
 | Rename it. |
 | Select the original Hand, Forearm and Arm bones. Make sure they have Attached to Parent turned Off. |
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The pose slider should be set to 100%. If it isn't put it there. With the hand bone selected create a new Orient-Like Constraint, target the IK_Hand bone. |
 | Create Orient-Like constraints for the forearm and arm bones, targetting the IK bones. |
 | Slide the pose-slider down to 0. |
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Open up the Orient-Like constraint in your timeline, select the Enforcement value. Zoom your timeline WAAAAAAY out until you can see the entire spline channel, it should have a step-shape like this. Basically the step-shape means that from 0-99% the Orient-Constrain is Off, but switches to full power once you hit 100%. That's no good. |
 | Select one of the points in the timeline, righ-click. Choose Interpolation Method > Linear. |
 | It should look like this now. The Orient constraint now changes values smoothly. |
 | Back in your modeling window (Bone Mode) Create a new bone, place it behind the arms. Call it Elbow. |
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Back to Pose Window. The slider should still be at 0. If you played with it to check the constraints, set it back. Unhide the HandTarget Bone. Select the Forearm, Kinematic-Constrain it to the HandTarget. Orient-Like Constrain the Hand to the HandTarget. And finally Aim-At the arm to the elbow. This is just like the leg setup we did in the last section. |
 | The IK part is complete! Now add an additional Orient-Like constraint to the original Arm, Forearm and Hand bones. |
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Move the slider to 100%. Open up the Orient Properties for the 2nd Constraints you just added. Enforcement should be 100%, set it to 0%. the timeline will now have another step-shaped spline. |
 | Set it to linear. Do this for all the new constraints. |
 | It's done! Time to cleanup. In your modeling window/bone mode you can hide Arm, Forearm, Hand, IK_Arm, IK_Forearm, IK_Hand. |
 | Also, use the J key to hide and unhide certain bones depending where the slider is. That way when you're in FK mode you only deal with FK bones. In IK mode you only deal with the IK Targets. |
 | Ik Mode - FK bones hidden. |