Limb IK

Overview

CryEngine's animation system allows to setup IK chains for characters.

When an IK chain is active, the system figures out the values for the joints that are part of the chain so that the end effector reaches the provided target position (if it's possible to reach it). The exact behavior for each chain and the amount of joints supported depends on the solver used.

Examples of systems that currently use LimbIK chains:

Setup

IK chains are defined in the chrparams file for a character

<Params>
  <IK_Definition>
    <LimbIK_Definition>
      <IK EndEffector="Bip01 R Hand" Handle="RgtArm01" Root="Bip01 R UpperArm" Solver="2BIK"/>
      ...
      <IK EndEffector="Bip01 L Foot" Handle="LftLeg01" Root="Bip01 L Thigh" Solver="2BIK"/>
    </LimbIK_Definition>
    ...
  </IK_Definition>
  ...
</Params>

The following summarizes the attributes that must be defined for each IK element.

EndEffector	Name of the joint that will try to reach the target location
Handle	Name used to identify the LimbIk definition. No more than 8 characters allowed. No two LimbIK definitions for a character should have the same Handle.
Root	Name of the starting joint for the IK chain
Solver	Name of the solver used to calculate the joint values when the chain is active.

These are the available solvers:

2BIK	2 bone IK
3BIK	3 bone IK
CCDX	Cyclic Coordinate Descent with X joints

Documentation

Limb IK

Overview

Setup