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

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.

Applications Entertainment Medicine / Sports Arts / Education Science / Engineering

Entertainment: Live Action Films

Entertainment: 3D computer animations

Entertainment: Video Games

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

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

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)

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 and keyframe animation is often used.

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.

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.

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.

Popular types of mocap equipment Magnetic systems Mechanical systems Optical systems

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

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

Mechanical systems Exoskeleton with angle sensors.

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.

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

Optical systems  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.

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.

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

Mocap animation pipeline 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.

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

Dr. Midori Kitagawa midori@utdallas.edu ATEC 1.909