In this lesson, you completed the animation of a mechanical arm model that picked up and moved a cargo box. You learned how to:

• Construct a model hierarchy to provide relationships between the components for posing and keyframing.
• Construct a single chain skeleton to pose the arm model using Inverse Kinematics.

  It is common to create characters with multiple joint chains. For example, two and four-legged characters would use multiple joint chain skeletons to assist with posing their hierarchical structure. For a tutorial on creating a multiple chain skeleton see Lesson 1: Skeletons and Kinematics (Introduction).

• Parent the components of the mechanical arm model into the skeleton hierarchy.

  Parenting is one method for combining a model into a skeleton hierarchy. When using characters that have bending or deforming features a more common technique is to use Skin > Bind Skin. For a tutorial on smooth skinning see Lesson 2: Smooth Skinning (Introduction).

  An easy method to parent one node to another using the Hypergraph is to drag one node over top of the other using your middle mouse button.

• Create an IK system with a control object for manipulation.

  It is very common to create characters with multiple joint chains and multiple IK handles to control them. Control objects simplify the selection and posing of the character.

• Use three types of constraints (Point, Orient, Parent) to control components of the IK system and other components in the scene.

  Constraints are useful for animating the attributes of one object based on the attributes of another. Other types of constraints not covered in this lesson include aim and scale constraints.

  Using the parent constraint, the platform could also be animated to move the cargo box as if it were on an elevator, or a conveyor belt.

• Apply limits to the movement of the IK system.

  In this lesson, you constrained the translation of the control object in order to constrain the movement of the IK. It is not recommended that you set limits on the rotation of an IK system as it limits how the solver calculates the position of the joints.

  Although not covered in this lesson, it is possible to simplify the display of attributes in the Channel Box so that only the animatable attributes associated with a character are displayed.

• Pose and set keyframes for an IK system.