Animation Lesson 5: Open the scene for the lesson
In this lesson, you work with a scene we created for your use. In the first steps of this lesson, you open
the scene and view the various elements that have been created for your use.
1. Make sure you've done the steps in Animation Lessons: Preparing for the lessons.
2. Open the scene named IK_MechArm.mb.
You can open the scene named IK_MechArm.mb from the Maya Documentation, Lessons, and
Extras CD or from the drive where you copied the Getting Started files.
The scene contains a model of a mechanical arm and a cargo box to be moved by the arm. The
components of the mechanical arm include:
o A cargo magnet cup on the end
o Three arm segments
o A base for the arm to swivel about
o A four-legged base for the assembly
To work with this model using IK you must create a hierarchy for it.
Understanding hierarchies
Inverse Kinematics relies on hierarchical relationships between the components of a model and the IK
system to pose and animate the components. Before using Inverse Kinematics it is important to
understand hierarchies in Maya.
A hierarchy is composed of a series of nodes that are combined for some purposeful relationship.
Individual nodes may represent the surfaces of a model, a network of textures that describe a shading
material, or series of joints in a skeleton. Hierarchies are structured in a top-down manner, with one node
at the top (the parent node or root node) and other nodes (child nodes or leaf nodes) attached and
interconnected beneath the top node.
Selecting the parent node at the top of the hierarchy also selects the items contained in the hierarchy
below. Selecting a child node lower in the hierarchy selects any child nodes that are lower in the
hierarchy.
Hierarchies allow you to create complex structures with relationships between components. For example,
when you animate a hierarchical model, you simply need to select and move the parent node of the
hierarchy and the rest of the model (child nodes) also moves.
Regardless of whether you decide to animate the mechanical arm using FK or IK, or a combination of
both methods on the same model, the best approach involves making the mechanical arm model into a
hierarchical structure.
Creating a hierarchy for the mechanical arm ensures that:
Components of the hierarchy can be rotated as if they were one unit. A common pivot point is
created at the parent node level. This allows the separate components to rotate as one unit
based on their membership in the hierarchy. For example, if the mechanical arm's base (parent
node) is rotated, anything lower down the hierarchy, for example, the mechanical arm which is
constructed of child nodes, will also rotate because of its membership and position in the
hierarchy.
When a particular segment of the model is posed and keyframed, the components that are lower in
the hierarchy are also posed and keyframed.
In this lesson, you work with a scene we created for your use. In the first steps of this lesson, you open
the scene and view the various elements that have been created for your use.
1. Make sure you've done the steps in Animation Lessons: Preparing for the lessons.
2. Open the scene named IK_MechArm.mb.
You can open the scene named IK_MechArm.mb from the Maya Documentation, Lessons, and
Extras CD or from the drive where you copied the Getting Started files.
The scene contains a model of a mechanical arm and a cargo box to be moved by the arm. The
components of the mechanical arm include:
o A cargo magnet cup on the end
o Three arm segments
o A base for the arm to swivel about
o A four-legged base for the assembly
To work with this model using IK you must create a hierarchy for it.
Understanding hierarchies
Inverse Kinematics relies on hierarchical relationships between the components of a model and the IK
system to pose and animate the components. Before using Inverse Kinematics it is important to
understand hierarchies in Maya.
A hierarchy is composed of a series of nodes that are combined for some purposeful relationship.
Individual nodes may represent the surfaces of a model, a network of textures that describe a shading
material, or series of joints in a skeleton. Hierarchies are structured in a top-down manner, with one node
at the top (the parent node or root node) and other nodes (child nodes or leaf nodes) attached and
interconnected beneath the top node.
Selecting the parent node at the top of the hierarchy also selects the items contained in the hierarchy
below. Selecting a child node lower in the hierarchy selects any child nodes that are lower in the
hierarchy.
Hierarchies allow you to create complex structures with relationships between components. For example,
when you animate a hierarchical model, you simply need to select and move the parent node of the
hierarchy and the rest of the model (child nodes) also moves.
Regardless of whether you decide to animate the mechanical arm using FK or IK, or a combination of
both methods on the same model, the best approach involves making the mechanical arm model into a
hierarchical structure.
Creating a hierarchy for the mechanical arm ensures that:
Components of the hierarchy can be rotated as if they were one unit. A common pivot point is
created at the parent node level. This allows the separate components to rotate as one unit
based on their membership in the hierarchy. For example, if the mechanical arm's base (parent
node) is rotated, anything lower down the hierarchy, for example, the mechanical arm which is
constructed of child nodes, will also rotate because of its membership and position in the
hierarchy.
When a particular segment of the model is posed and keyframed, the components that are lower in
the hierarchy are also posed and keyframed.
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