Motion Capture Animation &
Procedural Animation
Dr. Midori Kitagawa
Arts and Technology Program
University of Texas at Dallas
Gif animations by Dax Norman

• Keyframe animation
• Motion capture animation
• Procedural 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.

• 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.

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

• 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 subject’s movement.

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

• 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.

• 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.

• 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.

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.

• 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.

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

Entertainment: Live Action Films

Entertainment: 3D computer animations

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

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

• 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 roleplaying games)

• 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.

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

Disadvantages of mocap animation
• Cost.
• Manipulating mocap data is often difficult -> 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.

• Magnetic systems
• Mechanical systems
• Optical systems

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

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

• Exoskeleton with angle sensors.

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

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

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

• 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.

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

Preproduction
Capture -> data cleaning -> retargeting
Modeling -> rigging ----------------------------mocap animation
Keyframe animation
Effect animation
Sound design
Texturing/lighting -> Rendering -> Composition
Post-production
* Tasks that everyone should be involved.
* Tasks that can be designated to a member or members.

System Calibration and Capturing and Processing Data
2D Image -> 2D Camera Data -> 3D Markers Positions -> Trajectories -> Recon Skeleton -> Solver Skeleton
Circle fitting Triangulation Reconstruction
BLADE
Subject Calibration
• Capture Range of
Motion (ROM)
• Reconstruct trajectories of ROM
• Label markers
VST
(subject template)
The processes that you go through for each character
VSK
Skeleton with subject’s size & proportion
Mocap Pipeline
Flow Chart
FBX
Skeleton with subject’s size & proportion and motion data
MOTION
BUILDER
Character Setup
• Create a skeleton
• Bind skin to the skeleton
• Rig the character
The processes that you repeat for each shot
MB
Maya Scene File
FBX
Skeleton with 3D character’s size & proportion (and skin)
MAYA
Rendering
• Marge the rigged character (MB) and the skeleton with motion data (FBX)
• Edit motion (
IK/FK blend , Trax )
• Render
Character Setup
• Correlate :
Character
&
Character
(FBX)
•
Edit motion
• Bake motion data to the skeleton
FBX
Skeleton with motion data & 3D character’s size & proportion

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 – 3:45 pm
Spring 2016: ATEC 4345 Motion Capture Animation

Dr. Midori Kitagawa midori@utdallas.edu
ATEC 1.909