Using Inverse and Forward Kinematics

Using IK and FK

When making your skeleton, you can assign IK during their creation or you can add IK later.

Types of IK Solver

HD – History Dependent IK is used mostly for mechanical linkage

HI – Most commonly used

Limb – This is a subset for HI and is used for arms and legs

Spline IK – This is used for tails, tentacles etc.

When assigning IK during bone creation, you need to check, assign to root and assign to children.

When you want to assign a particular piece of IK to a bone, you need to got to the animation tab at the top of the interface > Solver > HI Solver. Click on the bone that you want the solver to start at, and then you drag an elastic band to the bone that you want the solver to end at. A blue cross will appear – this is your end affector/IK Handle.

Sometimes, you need to use FK. In order to do this you need to disable the IK to allow for more movement. To do this, click on the IK handle > motion panel > click the enable bar to turn off enable. You are now using FK.

The Swivel Angle

If your character squats down, for instance, the legs will turn outward. Click on the IK handle > go to swivel handle manipulator > pick on select and manipulate gizmo. You can now control the swivel angle using the gizmo

Limiting joints

You can limit joints and how much they rotate or swivel, but going to the hierarchy panel >IK. Here you can allocate just how much rotation you want on the IK. Do this in the local axis.

Switching IK and FK

Create a two bone chain. Go to the motion panel > Animate the IK at keyframe 20 and 40. At 41 Switch IK to FK by turning off the enable button. You can now grab the bone and rotate it freely. The goal of the IK change drags behind because it isn’t being used.