Forward and inverse kinematics

these terms come from robotics where engineers have to figure out how to move and rotate joints to get the effector to the position they need.

fK when any bone chain is rigged with fk it means that the bones are chained from parents to children. If you rotate bone 2, all of its children will rotate as well, which means that the bone 1 will not because it’s the parent of bone 2 and not it’s child. It’s useful since it created arc movements by default when joints travel along curved trajectories

Ik works in the opposite way, you loose the ability to animate every bone of the chain separately. With ik joints move in line trajectories unless you create the arc manually.

Methods for Fixing Knee/Elbow Popping

Rig a Solution

add a rig to eradicate the knee elbow popping. around the area via creating a cluster (a group of vertices, in this case grouping the leg and the knee together.

After, change the skin around the cluster through the geometry of the cluster to decrease the overall movement using the paint attributes tool.

However the cluster does not move around with the leg, the knee. That can be fixed by parent the cluster under the knee joint (relative attribute turned on, to move relative to the joint).

This method is useful to fix the problem in one dimension one direction, it would be difficult to fix it for a group of directions.

IK/FK Switch Rigging

How to rig the IK and FK switch to better understand the technology behind them. They joints I maya follow an hierarchy so they are linked and parented to each other and are connected and skinned to geometry. Altogether they function as an arm. The IK and FK are usually in the shoulder, elbow and wrist.

the way FK rig works is that each joint follows the parent joint’s behavior. If you rotate the shoulder, the elbow, wrist will follow.

Ik works inversely up the skeleton hierarchy. 

switch between the two joints when parented with the initial rig. Set driven key to switch between two sets of controlling points. Also set the visibility for when using one or another control.

Motion Path Animation

Motion paths give us the ability to move an element along a predefined path; for example by creating a spline curve could help animate a path for an object in 3D space. the curve pattern can be modified with vertices and when the object is animated using keys it displays the frame at which the object will be in space. with the motion path curve you are also able to change the orientation of the object, in this case the spaceship, to make it look less mechanical while it moves on the curve.