Introduction
Installation
Pre-Rigged Models
Rigging
Contact
Animation
IK Ranges
Aligning Chains
Chain Visibility
Pivoting
Motion Paths
Automatic Features
Follow Rotation
System
After you've established your IK ranges, you'll likely want to make adjustments to poses at the starts and ends of those ranges. These starts and ends are the frames where the FK chain of an assembled limb snaps to and lines up (aligns) with its related IK chain, in order to create a seamless transition between the two chains. In other words, these starts and ends are where the kinematic switching hand-off takes place.
The process of aligning the FK chain to the IK chain would normally take quite a bit of time and effort. Essentially, the process involves keyframing the IK animation bones, then adding 'copy-transform' constraints to the FK bones that target the IK bones, then applying the constraints and finally keyframing the FK bones. When done this way, this process is at best a time sink, so the Kinematic Tool comes with an easy and straightforward way to handle this process, through the "Align Chains" operator. (To see both the FK and IK chains while playing with alignment, make sure "Chain Visibility" is on: use the eye-icon available via the top right Kinematic Tool Settings drop down menu, or head to the Chain Visibility section to learn about other ways to work with it).
Beyond just aligning the FK chain to the IK chain at the current frame, the "Align Chains" operator actually batch aligns the FK chain to the IK chain along a number of "Kinematic Mode" property keyframes. The amount of keyframes where an alignment takes place is based on the "Manual Alignments" setting in the settings drop-down tab. The "Manual Alignments" number represents the amount of keyframes on each side of the current frame, plus the current frame if the current frame is sitting on a "Kinematic Mode" keyframe.
So if the "Manual Alignments" setting is at the default setting of 5, and you have 12 IK starts and ends before the current frame, and 7 IK starts and ends after the current frame, "Align Chains" will update and align at 10 points total, 5 on each side of the current frame. The reason this number is adjustable and not infinite is because the higher the number goes, the more likely the operator will begin to feel like it's taking time to complete its operation.
If you're used to the conventional kinematic switching system, you might be surprised to find that he "Align Chains" operator won't align the IK chain to the FK chain wherever there is an FK keyframe column, because there is no need to. The switch and hand-offs between the IK and FK chains only occur at the starts and ends of IK ranges, as the system is designed to do.
One thing to note: the "Align Chains" operator might not be able to properly align the FK chain to the IK chain if the axes of a single bone aren't uniformly scaled (for instance, just the x-axis is scaled) or are broken and separated from the rest of the bones. Experiment to see what the outcomes are before doing anything wild.
The "Align Chains" operator has an automatic updating version that is part of the Auto-update features of the Kinematic Tool. You can learn more about it in the Automatic Features section.
Next up, let's learn about Chain Visibility.