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,
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
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:
- You can rescale your entire hierarchy.
If you animate a robot, and then later decide you want to scale
the entire robot and its animation, link the robot's root object
to a dummy, link all of the robot's end effectors to the same dummy,
and then scale the dummy to scale all of the hierarchical objects
as well as the animation of the end effectors.
- You can use linked end effectors for
things like feet or hands. End-effectors are automatically bound
to the world, so when you move a root object in your hierarchy,
the end effectors remain behind. This is good for keeping feet on
the ground, but not very good for hands, where you want them to
move along with the character. To have hands follow the root object,
link the end effectors of the hands to the root object.
Linking Bones to Follow
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.
- Binding Objects (HD Solver)
binding functions in
the HD Solver to cause an object to attempt to maintain its position
and orientation relative to the world or to another object. A bound
object will resist motion in the kinematic chain until the chain
is stretched near its limits and the bound object must move to complete
the IK solution.
- Controlling IK Precision
Even with carefully
defined joint precedence and joint parameters there are many valid
IK solutions for any placement of an end effector. You set position
and rotation thresholds to control IK precision and solution speed.
- HD Solver Motion Panel Rollouts
To adjust the parameters
for all bones or hierarchically linked objects in the chain, you
select a single bone or object, and then adjust the parameters in
Motion panel Parameters to affect all the
bones or objects in the hierarchy.
- HD Joint Settings
You control a joint's
resistance to motion, and its tendency to return to its original
position, by setting Ease, Damping, and Spring Back options.