IART219220221 Animation Motion

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IART-219/220/221AnimationMotion

• ? Shape Animation
• ? Spatial Animation
• ? Inverse Kinematics
• ? Motion Capture

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Shape Animation

• Free-form
• 3D Morphing
• Free-form lattices
• Wave functions
• Animating surface characteristics

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Free-Form Shape Animation

• Interpolating between two versions of the same
  object
• Two versions at two keyframes
• Modify one or both mesh
• Use of locked points
• Squashing and stretching

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3D Morphing

• Interpolating between two different objects
• Animating all points of source object into
  corresponding position in target
• Same number of points
• Pre-planning
• Order of sequence

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3D Morphing
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Free-Form Lattices

• External control structure
• Manipulating large number of points
• 3D grid of control points connected to model
  points through imaginary springs
• Push and pull object points
• Larger number of control points, smoother moves

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Free-Form Lattices
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Wave Functions

• Again to help manipulate large number of points
• 2D math function curves to control shape
  animation
• Circular wave for a lake
• Planar wave for the surface of a sea
• Spherical wave for explosion
• Can be unpredictable

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Spatial Animation

• Moving objects in 3D space
• Interactive specification of key poses
• Simplest method
• Forward kinematics
• Motion paths
• Inverse kinematics

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Hierarchical Structures

• Grouping objects at different levels
• Inverted tree structure
• Levels of precedence
• Parent (e.g. Root)
• Child/Grandchild
• Sibling
• Articulated figures
• Connected objects
• Joints and degrees of freedom

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Hierarchical Structures
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Forward Kinematics

• Change in the angle of joints causes motion
• Joint angles are known in advance and will be
  repeated
• Angle values provided by keyboard or a specific
  device (physical model)

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Forward Kinematics
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Motion Path

• 3D path for motion is drawn
• Easy to work with
• Can be combined with other methods
• Path of a legged creature
• Steps
• Draw the path
• Select and link the object and set the front side
• Set speed and acceleration

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Motion Path
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Inverse Kinematics

• Complex models with large number of joints
• Motion of the entire skeleton based on the final
  angles of some key joints
• Needs hierarchical structure
• Articulated figures, skeleton,
• Includes chain, joints, motion constraints and
  (end) effectors

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Inverse Kinematics

• Articulated chain
• Root (first joint)
• Joints and segments
• Effector (determines the motion)
• Joints usually rotate around one axis
• In some cases FK can be more direct and offer
  better control

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Inverse Kinematics
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Motion Capture

• Alternative to keyframing
• May provide only basic tracks of motion
• Secondary motion added later
• XYZ joint positions
• Can be applied to IK skeleton
• Started in early 80s
• Potentiometers, LEDs and mechanical armatures

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Motion Capture Technology

• Prosthetic
• Based on potentiometers
• Very accurate but bulky and restricted
• Acoustic
• Radio signal transponder
• Magnetic
• Optical