CS 6353 CS 6353

Computer Graphics and Computer Graphics and MultimediaMultimedia

Motion CaptureMotion Capture

ByBy

Vanitha KowdeedVanitha Kowdeed

Overview:Overview:

Definition of Motion CaptureDefinition of Motion Capture History of MocapHistory of Mocap RotoscopingRotoscoping Types of Motion CaptureTypes of Motion Capture Prosthetic Prosthetic Optical Optical Electromagnetic Electromagnetic AcousticAcoustic Marker PlacementMarker Placement Production PipelineProduction Pipeline Objects for MocapObjects for Mocap Skin DeformationSkin Deformation ExamplesExamples ReferencesReferences

What is Motion Capture?

Motion Capture of an object involves sensing,digitizing, and recording that object in motion– Whole body– Hands– Face• One way of acting out an animation

Or

A process by which a movement can be recorded digitally.

Originally used for military tracking purposes.Originally used for military tracking purposes. In sports, motion capture acts as a tool for In sports, motion capture acts as a tool for biomechanic research that is focused on the biomechanic research that is focused on the mechanical functioning of the body, like how the heart mechanical functioning of the body, like how the heart and muscles work and move.and muscles work and move.

History of Motion CaptureThe Motion Capture began in late 1800’s when Etienne The Motion Capture began in late 1800’s when Etienne Jules Marey and Eadweard Muybridge performed Jules Marey and Eadweard Muybridge performed motion studies on various animals and humans.motion studies on various animals and humans.

Etinne Jules Marey’s Etinne Jules Marey’s

Motion Capture SuitMotion Capture Suit

History of Motion Capture (Contd.)History of Motion Capture (Contd.)

Eadweard Myubridge

•Historically, Motion Capture in animated movies was created using the extension of "ROTOSCOPING" technique.

Rotoscoping is an animation Rotoscoping is an animation technique in which the technique in which the animators trace over live-animators trace over live-action film movement frame action film movement frame by frame, for use in animated by frame, for use in animated films. The pre-recorded live-films. The pre-recorded live-action film images are action film images are projected onto a frosted glass projected onto a frosted glass panel and are re-drawn by an panel and are re-drawn by an animator. This project animator. This project equipment is called rotoscope.equipment is called rotoscope.

Tom Goes To The

Mayor

There are primarily five methods in There are primarily five methods in motion capture. They are :motion capture. They are :

Prosthetic (or Electromechanical)Prosthetic (or Electromechanical) AcousticAcoustic ElectromagneticElectromagnetic Optical fiberOptical fiber OpticalOptical

Prosthetic Motion Capture Prosthetic Motion Capture uses Potentiometers on the uses Potentiometers on the aforementioned plastic aforementioned plastic exoskeleton that an actor exoskeleton that an actor must “wear”, and then act must “wear”, and then act out his or her movements. out his or her movements. This is very accurate and This is very accurate and transmits real-time data at a transmits real-time data at a far greater range than any far greater range than any other technology.other technology.

A gypsy3 prosthetic suite

Fiber Optic sensorsFiber Optic sensors Rotation based on Rotation based on

transmitted lighttransmitted light

This approach has a central This approach has a central magnet with several magnet with several receivers attached to the receivers attached to the actor’s body. The receivers actor’s body. The receivers capture and record the actors capture and record the actors movements and save them movements and save them to the computer. This to the computer. This motion capture method can motion capture method can be hindered by nearby metal be hindered by nearby metal objects if they are large objects if they are large enough and depending on enough and depending on the power of magnets being the power of magnets being used.used.

A suit with magnetic sensors

Acoustic Motion Capture uses audio transmitters on the actor’s Acoustic Motion Capture uses audio transmitters on the actor’s body that make a “clicking” sound when activated by body that make a “clicking” sound when activated by movement. Receivers measure the time it takes for the sound movement. Receivers measure the time it takes for the sound to reach them and triangulate the data to indicate a point on a to reach them and triangulate the data to indicate a point on a 3D plane. This method has a problem of audio interface that 3D plane. This method has a problem of audio interface that effects the accuracy of the motion capture. And the other effects the accuracy of the motion capture. And the other disadvantages are as follows:disadvantages are as follows:

Limited RageLimited Rage Limited number of sensorsLimited number of sensors Cables on bodyCables on body

•Reflective Markers•Multiple Cameras that digitize different views of performance.

Motion Capture Systems

Inside-In

Inside-Out

Outside-In

•Electromagnetic

•Acoustic•Optical

•Electromechanical

•Optical Fiber

Location should Location should move rigidly with move rigidly with jointsjoints

Stay away from Stay away from bulging musclesbulging muscles

Production Pipeline

Sensor Calibration

Subject Calibration

Record Movements

Compute the position and orientation of camera/transmitter

Place markers on body, compute skeleton structure(lengths of links)

Marker positions (and orientations) varying over time

Marker Data Cleanup

Convert to Joint Angles

Occlusion and correspondence problems

Occlusion and correspondence problems

Mapping to characters

Direct Mapping or retargetting

Details to be taken Care of at time of Motion Capture:

•What we need is– Position and orientation of the root segment– Joint angles– Length of each link (is it possible ?)– Skeleton connectivity– Skin deformation• The mocap system actually provides– Marker positions on the skin, or– The positions and orientations of markers

Types of Objects that can be had motion capturing

•Human whole body•Portions of body•Facial animation•Animals•Puppets•Other objects

What is Captured ?

Skin Deformation:

References:

•Motion Capture- http://en.wikipedia.org/wiki/Motion_capture

•A Brief History of Motion Capture for Computer Character Animation- http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/motion_capture/history1.htm

•Computer Graphics World-  http://www.cgw.com/ME2/dirmod.asp?sid=&nm=&type=Publishing&mod=Publications%3A%3AArticle&mid=8F3A7027421841978F18BE895F87F791&tier=4&id=A8B4004315A84A5089255A2E366E2E78

•Motion Capture- What is it? - http://www.metamotion.com/motion-capture/motion-capture.htm

•ACCAD-Motion Capture Lab-Home, information and documentation-  http://accad.osu.edu/research/mocap/mocap_home.htm

References (contd..)

•Motion Capture-  http://www.postmagazine.com/ME2/dirmod.asp?sid=&nm=&type=Publishing&mod=Publications::Article&mid=8F3A7027421841978F18BE895F87F791&tier=4&id=C715B81DD6674D62BD666D304D2E8D0B

•Motion Capture- http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2005/Motion_Capture_KHY6_DCL34/Motion_Capture.htm

•Practical Motion Capture in Everyday Surroundings-   http://www.youtube.com/watch?v=V0yT8mwg9nc

•Motion Capture- http://web.mit.edu/comm-forum/papers/furniss.html

•Motion Analysis Studios- http://www.mastudios.com/index.html

Any Questions ????????Any Questions ????????

Thanks !!!!Thanks !!!!