Using inverse kinematics
requires that you set parameters for a number of IK components.
Brief definitions of these components follow; details are provided
in other topics.
Note3ds Max Design offers
a variety of inverse kinematics systems. There are four kinds of
IK solvers, plus applied IK and interactive IK systems that don't
use IK solvers. Not all of the following parameters are used by
all the systems.
- IK Solvers
An IK solver applies
an IK solution to a kinematic chain. The kinematic chain is composed
of a bones system, or a set of linked objects.
An IK joint controls
how an object transforms with respect to its parent. You specify
joint behavior with settings in three categories:
- Object Pivot PointThe
location of an object’s pivot point defines where joint motion is applied.
- Joint ParametersChanging
the IK settings in the Hierarchy command panel determines the direction,
constraints, and order of how the joint operates.
- Parent Pivot PointThe
location of an object’s parent pivot point defines the origin from which
the joint constraints are measured.
The commands you use
to place the pivot points for both the object and its parent are
- Start and End Joints
The start and end joints define
the beginning and end of an IK chain managed by the IK solver. The
hierarchy of the chain determines the direction of the chain. The pivot
point of the end joint is displayed as the end effector, when end
effector display is enabled.
- Kinematic Chain
Inverse kinematics calculates
the position and orientation of objects in a kinematic chain. The
kinematic chain is defined as any part of a hierarchy under IK control.
The IK chain starts with a selected node and consists of a start
joint and an end joint. The base of the chain is either the root
of the entire hierarchy, or an object that you specify as a terminator
for the chain. The kinematic chain is defined when you apply an IK
solver to a chain, or when you create a bone chain with an IK solver
The goal is used by the
HI Solver to manipulate the end of the chain. When the goal is animated,
the IK solution attempts to match the end effector (pivot point of
the last child in the chain) to the goal position. When using an
HD Solver, the end effector fulfills the same function as the goal.
- End Effector
For any IK solution,
you explicitly move a control object. IK calculations then move
and rotate all other objects in the kinematic chain to react to
the object you move. The object that you move is the goal, in an
HI Solver or IK Limb Solver, or in the case of an HD Solver, an
- Preferred Angle
Determines which direction
a joint will bend. The preferred angle establishes a base angle
between chain elements when an HI Solver is applied. The IK Solution seeks
this angle in calculations.
- Solver Plane and Swivel Angle Manipulator
A plane can be defined between
the start and end joints, which aids in controlling the IK solution.
Adjust or animate the solver plane by changing the swivel angle manipulator
when in manipulate mode. This determines an up-vector handle for
the chain, which can also be animated over time. You can also define
a target for the swivel angle manipulator to follow. For more information, see
White Paper: Swivel Angle of the HI IK Solver.
You can explicitly set
the base of an HD (History-Dependent) IK chain by defining one or
more objects as terminators. A terminator object stops the IK calculations
so that objects higher up the hierarchy are unaffected by the IK
solution. Terminator objects are also used to define hierarchies
that use multiple HD IK chains.
Terminator objects are
not used in HI Solvers or IK Limb Solvers. In these cases the termination
is determined by the end joint of the chain.
- Bound Objects
Objects in your hierarchy can
be bound to the world, or they can be bound to other objects called
Binding allows objects
in your hierarchy to be influenced by objects that are not part
of the hierarchy.
- An object bound to the world will attempt
to maintain its current position and orientation.
- An object bound to a follow object will
attempt to match the position and orientation of the follow object.
- You can bind to a follow object when
you use an HD Solver, or when Applied IK is used. If you want to
bind to a follow object when using an HI or IK Limb Solver, apply
a position constraint between the goal and any follow object of
your choice (usually a point, dummy, spline, or bone).
- Enabled IK
(HI Solver) When using the
HI Solver, you can animate with either inverse kinematics or forward
kinematics (FK). When Enabled is turned on, inverse kinematics controls
the chain, and keyframes are placed only on the goal. When Enabled
is turned off, forward kinematic rotational keys are placed on all
- IK/FK Snap
(HI Solver) When using the
HI Solver, if you animate using both IK and FK, you might create
a situation where the goal has moved away from the end of the chain, causing
a jump in the animation. Pressing IK/FK Snap will result in the
goal being moved back to match the position of the end effector, eliminating
the jump in the animation.
- IK for FK pose
(HI Solver) When this button
is turned on, moving the goal automatically sets rotation keys for
the bones. In effect, this lets you use IK manipulation to create
your pose, setting FK keys.