History-Dependent (HD) IK Solver
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Select a node of hierarchy or bone chain. Animation menu IK Solvers HD Solver Click a second node of chain.

Animating with the HD Solver lets you use sliding joints combined with inverse kinematics. It has controls for spring back, damping, and precedence not found in the HI Solver. It also has quick tools for viewing the initial state of the IK chain. Use it for animations of machines and other assemblies. Since this is history dependent, performance is slower at the end of long animations. For lengthy scenes, use HI Solvers, if possible.

Animating the End Effectors

You animate a hierarchy of objects or bone structure using HD Solvers by animating special end effectors located at the bone joints. There are two types of end effectors: Position and Rotation. They are displayed as three intersecting blue lines at the joint.

When you select and transform a joint that carries either end effector, only the end effector itself is transformed. The objects or bones in the chain then use IK to calculate the IK solution.

Animating these end effectors is much like animating with Interactive IK except interpolation between keyframes uses correct IK solutions.

Linking End Effectors to a Parent

You can link HD IK end effectors to a parent to achieve results similar to using bound follow objects with Interactive and Applied IK. To link a HD IK end effector, you click Link on the Motion panel.

There are two reasons to link an end effector to a parent:

Linking Bones to Follow Objects

You can also use follow objects instead of end effectors and bind bones to any number of follow objects using Interactive IK.

If you use follow objects with HD IK, you do not need to click Apply IK. The IK solver takes care of everything automatically.

See Also