Motion Capture Animation

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Motion Capture Animation Procedural Animation

• Dr. Midori Kitagawa
• Arts and Technology Program
• University of Texas at Dallas

Gif animations by Dax Norman
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Three types of 3D computer animation

• Keyframe animation
• Motion capture animation
• Procedural animation

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Keyframe Animation
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Keyframe animation

• Keyframe is a drawing of a key moment in an
  animated sequence, where the motion is at its
  extreme.
• Inbetweens fill the gaps between keyframes.
• Every motion is created by animators.

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Keyframe animation

• To produce 3D keyframe animation, the animator
  builds the behavior of a 3D model by keying
  parameter values in key frames where the values
  are at their extremes.

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Keyframe animation

• 3D keyframe animation method is based on
  traditional hand-drawn 2D keyframe animation
  method.
• Animation is manually produced from scratch.
• Examples Pixar animations

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Motion capture animation
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Motion capture animation

• To produce a motion capture animation, the motion
  of a capture subject is recorded as 3D data and
  applied to a 3D model.
• The animation is produced from the capture
  subjects movement.

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Motion capture animation

• Although no 3D data is involved in rotoscoping,
  motion capture technology is sometimes referred
  as devils rotoscoping.
• Examples Avatar (2009), How to Train Your Dragon
  2 (2014)

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Procedural animation
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Procedural animation

• To produce a procedural animation, the animator
  defines a procedure or a set of operations to be
  performed.
• Each operation can generate or alter data that
  passes through it and can be conditionally or
  non-conditionally executed.

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Procedural animation

• With procedural animation methods (e.g., particle
  systems, rigid dynamics and flexible dynamics),
  the user specifies a set of rules, initial
  conditions and parameter values and runs
  simulations.
• Physics-based animation is a subset of procedural
  animation.

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Procedural animation

• Procedural methods can be used in any part of
  production pipeline to produce geometries,
  textures, lights, rigs, animation, composites,
  sounds and other elements.
• Examples visual effects (e.g., smokes, steam,
  fire, clouds, dust, water, and plants) in live
  action films and 2D/3D animations.

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ATEC 4371 Topics in Animation Procedural
Methods for Computer Animation

• Fall 2015 Semester
• Prerequisite ATEC 2326 Computer Animation
  Process
• Textbook The Art of 3D Computer Animation and
  Effects, 4th Edition by Isaac Kerlow
• Software Houdini (Side Effects Inc. ) which is
  node-based.

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More about motion capture animatoin
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What is Mocap?

• Motion capture (mocap) is sampling and recording
  motion of humans, animals, and inanimate objects
  as 3D data.
• The data can be used to study motion or to give
  an illusion of life to 3D computer models.

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Applications

• Entertainment
• Medicine / Sports
• Arts / Education
• Science / Engineering

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Entertainment Live Action Films

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Entertainment 3D computer animations
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Entertainment Video Games
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Medicine / Sports

• Medicine (e.g., gait analysis, rehabilitation)
• Sports (e.g. injury prevention, performance
  analyses, performance enhancement)

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Arts / Education

• Dance and theatrical performances
• Archiving (e.g., Marcel Marceau)

OSU/ACCAD
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Science / Engineering

• Engineering (e.g., biped robot developments)
• Computer Science (e.g., human motion database,
  indexing, recognitions)
• Design (e.g., ergonomic product design)
• Military (e.g., field exercises, virtual
  instructors, and role-playing games)

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Mocap animation

• Motion capture animation is different from
  keyframe animation in terms of how motion is
  created.
• Same principles of animations apply to mocap
  animation keyframe animation!
• Combination of motion capture animation, keyframe
  animation and procedural animatoin is often used.

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Advantages of mocap animation

• Faster to create (only if an established
  production pipeline exists.)
• Secondary motions and all the subtle motions are
  captured.
• -gt more realism
• Physical interactions between performers and
  props can be captured.
• -gt more realism

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Disadvantages of mocap animation

• Cost.
• Manipulating mocap data is often difficult -gt
  Re-capturing or key framing a shot with bad data
  is often easier.
• Mapping mocap data of a performer to a 3D
  character with a different proportion may cause
  issues.

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Popular types of mocap equipment

• Magnetic systems
• Mechanical systems
• Optical systems

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Magnetic systems

• Utilize sensors placed on the body to measure the
  magnetic field generated by a transmitter source.

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Magnetic systems

• ? Require no special lighting condition.
• ? Sensors are never occluded.
• X Affected by electromagnetic force.

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Mechanical systems

• Exoskeleton with angle sensors.

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Mechanical systems

• ? Measure joint angles (no marker ID problems).
• ? Sensors are never occluded.
• X Breakable!
• X Configuration of sensors is fixed.
• X Constrains on joints.

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Optical systems

• The cameras are equipped with infrared LED's and
  filters.
• The cameras see reflector markers.

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Optical systems

• ? Higher sampling rate.
• ? Larger capture space.
• X Markers are sometimes occluded -gt marker ID
  problems.
• X Provide only positional data -gt joint angles
  need to be computed.

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Mocap system at UTD

• Vicon optical system
• 8 high-speed MX 13 (up to 10,000 fps) and 8
  high-resolution MX 40 (4 megapixels) cameras.
• Capture up to 5 performers at once.

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Mocap animation courses

• Graduate level ATEC 6352 UG level ATEC 4345
• Group project based
• Group of 3 to 5 members
• Semester long project
• Pre-requisite
• ATEC 3317 Modeling and texturing
• OR
• ATEC 3327 Lighting and composition
• Recommended
• ATEC 3328 Rigging I
• ATEC 4337 Computer Animation

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Mocap animation pipeline

• Preproduction

Capture -gt data cleaning -gt retargeting Modeling
-gt rigging -----------------------------
mocap animation Keyframe animation Effect
animation Sound design Texturing/lighting -gt
Rendering -gt Composition

• Post-production
• Tasks that everyone should be involved.
• Tasks that can be designated to a member or
  members.

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2D Image -gt 2D Camera Data -gt 3D Markers
Positions -gt Trajectories -gt Recon Skeleton -gt
Solver Skeleton
System Calibration and Capturing and Processing
Data
FBX
Triangulation
Reconstruction
Circle fitting
Skeleton with subjects size proportion and
motion data
BLADE

Subject Calibration
VSK
MOTION BUILDER
VST (subject template)

• Capture Range of Motion (ROM)
• Reconstruct trajectories of ROM
• Label markers

Skeleton with subjects size proportion
Mocap Pipeline Flow Chart
Character Setup
The processes that you go through for each
character

• Correlate
• Character
• Character
• (FBX)
• Edit motion
• Bake motion data to the skeleton

FBX
Character Setup

• Create a skeleton
• Bind skin to the skeleton
• Rig the character

Skeleton with 3D characters size proportion
(and skin)
MAYA
The processes that you repeat for each shot
FBX
Rendering

• Marge the rigged character (MB) and the skeleton
  with motion data (FBX)
• Edit motion (IK/FK blend, Trax)
• Render

MB
Skeleton with motion data 3D characters size
proportion
Maya Scene File
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UG Mocap Procedural Animation course schedule

• Summer 2015 ATEC 4345 Motion Capture Animation
• Prerequisite ATEC 3317 Modeling and texturing
• OR
• Prerequisite ATEC 3327 Lighting and composition
• Mondays 1- 5 pm
• Fall 2015 ATEC 4371 Topics Procedural Methods
• Prerequisite ATEC 2326 Computer Animation
  Process
• Mondays 1 345 pm
• Spring 2016 ATEC 4345 Motion Capture Animation

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• Dr. Midori Kitagawa
• midori_at_utdallas.edu
• ATEC 1.909