Character Setup

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Character Setup

• Character Setup is the process of creating
  handles and controls for anything that a
  character animator will need to adjust in order
  to create performance. Generally this process
  involves creating a skeleton for each character
  model and attaching that skeleton to the
  character model. Some of the skill sets that
  make up a good character setup artist are
  sculpture, anatomy, animation, physic, and figure
  drawing.

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Character Setup

• Character setup always occurs after modeling
  during the production pipeline. In many cases
  character riggers will work with a model and send
  it back to modeling in order to add detail to
  areas that will require more detailed deformation
  that what is currently available with the model
  geometry.

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Character Setup

• In large production studios character setup is an
  extremely involved process that requires
  character riggers to create physically accurate
  muscle systems that deform in a realistic manner
  when the character model is animated. Character
  setup has become an extremely advanced field that
  is often overlooked when a casual observer
  watches computer animation. Character setup
  artist often work hand in hand with character
  animators in order to prepare the character rig
  for the exact type of motion the animator is
  looking for. Often times once an initial rigging
  pass is completed on a character, the rig is
  given to an animator to test and break the rig.

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Skeletons

• A skeleton is an armature that is built separate
  from a model that drives motion of the model
  geometry. A skeleton is created and then
  attached to geometry using different process
  depending how the model needs to move or deform.
  A skeleton is set up in a hierarchy where joints
  are parented to joints further up the hierarchy.

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Kinematics

• Kinematics are the mechanics of motion. In
  Computer Graphics kinematics describe the process
  which determines how a model moves during
  animation. During preproduction character setup
  artist work with the director and animators to
  determine the what type of kinematics system will
  be used to rig the character models based upon
  what is the desired motion

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Forward Kinematics

• Forward Kinematics involves rotating and
  positioning each joint into position as you move
  down the hierarchy. The rotation of a joint
  affects the position of all the bones and joints
  that are beneath it in the hierarchy. FK is
  similar to the animation techniques used by
  traditional stop motion animators where each
  joint is positioned individually as you move from
  the center of the model out. For example you
  would move the shoulder before the upper arm, the
  upper arm before the forearm, the forearm before
  the hand and the hand before the fingers.

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Inverse Kinematics

• Inverse Kinematics is the process of determining
  the joint angles and positions needed in order to
  create a desired pose. Instead of rotating each
  joint individually down the hierarchy, Inverse
  Kinematics allows the animator to position the
  end joint of a skeleton in one pose and the IK
  setup will determine all of the joint angles
  needed to create that pose. Setting up IK
  controls is an involved process that requires the
  character rigger to know which angle is the
  preferred angle of movement for a joint.

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Bind Pose

• The Bind pose for a model is the position of both
  the geometry and the skeleton at the time when
  the skeleton is attached to the model. The most
  common bind pose is the standard T position
  where a characters is standing up straight with
  arms fully extended out and legs close together.
  In many cases the final use for the character rig
  will determine what bind pose will be most
  efficient. If a character model is will not be
  deforming a great deal, a more relaxed arms
  down pose might be a better bind pose. In Maya,
  the bind pose is the transform values of the
  skeleton and model at the time when you bound
  them.

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Root Joint

• The root joint is the top joint in a skeleton
  system, every other joint in the skeleton is a
  child of the root joint. Generally for character
  animation the root joint is the pelvis. This
  will serve as the center of balance for the
  character. When the root joint is moved the
  entire skeleton and anything attached will move
  with it.

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Parenting

• In some cases attaching geometry to the skeleton
  is as simple as parenting the geometry directly
  to the joints. This is generally used for simple
  characters or situations where geometry does not
  deform or bend like a simple robot character or
  mechanical hinge. Each piece of geometry is
  parented to its corresponding joint.

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Skinning

• In most cases geometry has to be attached to a
  skeleton through a process called skinning. This
  process involves binding groups of vertices or
  CVs to the skeleton allowing the geometry to
  deform based on movement of the underling
  skeleton or muscle system.

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Rigid Bind

• Rigid binding is considered simpler that smooth
  binding because no control point is influenced by
  more that one joint. It is useful for creating
  defined hard creases. Rigid binds work great for
  anything that is non-deforming like hard surface
  models or mechanical objects.

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Smooth Bind

• A smooth bind allows control point to be
  influenced by more that one joint creating
  smoother more organic deformations. A joints
  influence varies across a surface as the control
  points move farther away from the joint. The
  amount of influence joints have on a control
  point must be normalized. This means that all of
  the influences on a control point need to add up
  to 1.

Rigid Bind
Smooth Bind
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Smooth Bind

• In Maya a smooth bind can be applied using
  Closest Joint or Closest Distance. Closest joint
  assigns control point to the nearest joint in the
  hierarchy. This is common when skinning
  characters because it pays attention to the
  skeleton hierarchy. Closest Distance assigns
  influence based on how far the the control point
  is from each joint.

Maya also has gives the user controls over the
maximum number of joints that can influence a
control point and the rate at which influence
drops off as a surface point moves farther away
from each joint. Max Influences determines how
many joints can influence 1 control point. This
is important in determining how . A max
influence of 1 can be thought of as a rigid bind.
Drop off Rate determines how much a joints
influence drops off as con
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Painting Weights

• A smooth bind is usually editing with a process
  called painting skin weights which involves
  adjusting the amount of influence a joint has
  across a surface. Since skin weights must be
  normalized, when the influence of one joint is
  decreased the influence is transferred to other
  joints in the hierarchy that have influence of
  that control point or area This process takes
  time, but is required to refine way a surface
  deforms as it moves.