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Motion Capture Glossary

A __ B __ C __ D __ E __ F __ G __ H __ I __ J

K __ L __ M __ N __ O __ P

Q __ R __ S __ T __ U __ V __ W __ X __ Y __ Z

A

Abduction: Rotation of a joint in such a way that the link moves away from the center of the body.
Actor: The link structure that controls the character in 3D animation software.
Adduction: Rotation of a joint in such a way that the link moves toward the center of the body.
Animation: 2D or 3D images displayed in such a way that they appear to the audience as if they are moving.
Animator: An artist who specializes in animation.
Arm Tape: A ShapeTape™ worn on the arm.
Axis: The planes of a 3D coordinate system are defined by an X axis, a Y axis and a Z axis. Each of these axes are at right angles to the other two.

B

Biomechanics: The mechanical analysis of the motion of living beings.
Blend: Morphing two animations together in order to make one longer animation. Often animation sequences are composed of several short animations blended together.
Butterworth Filter: A software filter used to reduce noise, thus smoothing data.
BVH Data: A type of data format used for motion capture data that uses a skeletal hierarchy and local joint angles. BVH stands for Biovision hierarchical data, Biovision is a motion capture services company and they developed BVH data as a means to share their data with their customers.

C

C3D Data: The C3D format is a public domain, binary file format that is used in Biomechanics, Animation and Gait Analysis laboratories to record synchronized 3D and analog data. It is supported by almost all 3D Motion Capture System manufacturers, as well as other companies in the Biomechanics, Motion Capture and Animation Industries.
Camera: A motion capture camera tracks markers on the moving body. Several cameras are required in order to track the markers.
Camera View: A view of a 3D animation scene defined by the animator.
Capture: The act of collecting data by means of a motion capture system. ‘Capture’ is also an action involved in the calibration of Measurand Inc.’s ShapeWrap II™ Motion Capture System where the Homing Pose is assumed by the subject and the shape of the ShapeTapes™ is recorded.
Cartesian Coordinates: X, Y and Z position. Each point in space has an X value, a Y value and a Z value governed by how far that point is from the origin of the coordinate system.
Character: The animated persona controlled by the actor.
Clean-up: The work done on animation data to eliminate inaccuracies or modify the motions.
Coordinate System: A set of three axes at right angles to one another making three planes. The three axes intersect at an origin from which points can be measured with coordinates measured along each axis.
Counterstrike: An online 3D first person shooter game that uses the Valve Half Life 2 game engine.
Cycling: An animation technique where the animator takes one move and repeats it in order to make a longer move. An example would be using one gait cycle several times in a row as opposed to animating several gait cycles.

D

Dance: Human motion presented in an artistic fashion, often with music. Motion Capture is now a popular means of enhancing dance and performing arts.
Data: Motion capture data is electronic information collected by a motion capture system. The data can be converted into different formats for different applications.
Data Glove: A term often used to describe a hand motion capture system.
Developer: One who designs new hardware or software.
Dorsiflexion: Motion of the foot with respect to the shin in such a way that the foot approaches the shin.
Dropout: Data loss during motion capture, often due to difficulty with wireless data transfer.

E

End Effector: A device connected to the end of a robotic arm in order to perform a task.
Enveloping: A 3D animation technique that makes the polygon structure making up the surface of a character follow the links inside the structure.
Ethernet: A communications protocol.
Eversion: Rolling of the ankle inward towards the center of the body.
Extension: The opening of a joint.

F

Filter: A software tool used to reduce noise in motion capture data thus making the data smooth.
Flexion: The closing of a joint.
Forward Kinematics: Determining the position and orientation of the end effector using the joint angles of the links.
Function Curve: A graphical representation of the position, orientation or scale of an animated parameter.

G

Gait: Walking, running or moving on foot.
Gait Cycle: One gait cycle involves one complete step with each foot.
Gender Specific Motion: Motion that is specific to either males or females. Exaggerated walks often exhibit gender specific motions.
Global Coordinate System: The world coordinate system that never moves. It is the origin from which all global data is measured. It’s the same as the world coordinate system.

H

Halflife 2: A 3D video game by Valve.
Hand Motion Capture: Motion capture of the hand, fingers and thumb.
Head Orientation Sensor: The orientation sensor worn on the head to collect head rotation data with the ShapeWrap II™ Motion Capture System.
Heel Strike: The instant of heel contact of the advancing foot during a gait cycle.
Homing: ‘Homing’ is an action involved in the calibration of Measurand Inc.’s ShapeWrap II™ Motion Capture System where the Homing Pose is assumed by the subject and offsets on the ShapeTapes™ are refreshed.
Hyperextension: Extension of a joint beyond its normal range of motion.

I

Infrared Sensor: Motion sensing technology that uses infrared light.
Inverse Kinematics: Determining joint angles based on the position and orientation of the end effector.
Inversion: Rolling of the ankle outward from the center of the body.
IQ: Software used with the optical Vicon motion capture system.

J

Jack: A video camera based motion analysis system.

K

Kaydara: 3D animation software company recently purchased by Autodesk.
Keyframe: An animation technique where the animator moves the animated links manually to get the desired motion.
Kinematics: The study of motion without considering the forces causing the motion.
Knee Bend Sensor: A 1 DOF bend only sensor developed and produced by Measurand Inc. Typically this sensor is used to measure knee flexion / extension.

L

Leg Tape: A ShapeTape™ worn on the leg.
Local Coordinate System: A coordinate system on a link with which distal link motion is often referenced.
Locomotion: Self powered transportation.

M

Machinima: Art and entertainment developed using a game engine.
Marker: A reflective point used to track a location on a body with optical motion capture systems. Cameras track markers thus capturing motion.
Marker Swapping: Occurs when the tracking cameras of an optical motion capture system confuse two or more markers. This causes errors and inaccuracies in motion capture data.
Mocap: Short for motion capture.
Motion Analysis: An optical motion capture system.
Motion Capture: Acquisition of shape and motion data from subjects for the purpose of study or for animating virtual characters and objects. Motion capture may be done by measurements within the confines of external fields (optical, magnetic, or acoustical), or by sensors affixed to the subject alone (portable motion capture). .

N

Natural Motion: A 3D character animation software package.
Non Player Character: A player in a video game that is never controlled by the player.
NPC: Short for non player character.

O

Occlusion: Occurs when the tracking cameras of an optical motion capture system don’t see a marker on the subject.
Optical Motion Capture System: A motion capture system which uses cameras that track markers mounted on the moving subject.
Orientation: The data representing the rotations that a link has performed.
Orientation Sensor: A sensor that measures the rotations that a link performs. Often orientation sensors use gyros, accelerometers and magnetometers.

P

Pelvic Orientation Sensor: The orientation sensor worn on the pelvis to collect pelvic rotation data with the ShapeWrap II™ Motion Capture System.
Pitch: Rotations about the Z axis when the Z axis extends laterally through the body.
Position: The data representing the translations of a point.
Plantarflexion: Motion of the foot with respect to the shin in such a way that the foot moves away from the shin.

Q

R

Ragdoll: An animation technique where all the links of a body are limp and subject to forces and the subsequent animator defined physics.
Right Hand Rule: When virtually gripping an axis with your thumb pointing in the positive direction your fingers curl in the direction of positive rotation. When virtually pointing in the direction of the positive X axis and curling your fingers in the direction of the positive Y axis, your thumb will point in the direction of the positive Z axis.
Robotics: The science of controlling the motions of mechanical links.
Roll: Rotations about the X axis when the X axis extends forward through the body.
Rotation: A change in orientation of an object.

S

S700: Measurand Inc.’s 1 DOF joint angle sensor often used on the knee.
S720: Measurand Inc.’s 1 DOF joint angle sensor often used on smaller joints like fingers.
S290: A data acquisition unit that works with the ShapeWrap II™ Motion Capture System to collect data from different sensors.
ShapeAnimator™: A multi-purpose animation tool that uses ShapeTape™ hardware.
ShapeHand™: Measurand Inc.’s hand motion capture device. It measures full finger, thumb and wrist motions using ShapeTape™ technology.
ShapeWare™: Matlab based software for recording and displaying real time ShapeTape™ data.
ShapeWrap™: ShapeWrap II™’s predecessor. ShapeWrap™ is no longer in production.
ShapeWrap II™: Measurand Inc.’s full body, portable motion capture system. ShapeWrap II™ is used around the world by animation schools, research facilities, and many others. It uses ShapeTape™ technology to capture motion.
ShapeRecorder™: Measurand Inc.’s software used to capture and record motion and display real time data. ShapeRecorder™ works with ShapeWrap II™, ShapeHand™, ShapeClaw™ and ShapeAnimator™.
ShapeSensor™: Refers to Measurand’s 1 DOF join angle sensors the S700 and the S720.
ShapeTape™: Measurand Inc.’s fiber-optic bend and twist sensors. ShapeTapes™ are used for many motion sensing applications, including motion capture.
ShoulderTape™: Measurand Inc.’s device that measures shoulder translations using ShapeTape™ technology.
Steam: An online place that hosts multi-player games like Counterstrike and Half-life 2.
Support Phase: The time during a walk cycle when a leg is in contact with the ground. Single support has only one foot on the ground, dual support has both feet on the ground.
Swing Phase: The time during a walk cycle when a leg is not in contact with the ground but rather is swinging through the air.

T

Thoracic Orientation Sensor: The orientation sensor worn on the torso to collect thoracic rotation data with the ShapeWrap II™ Motion Capture System.
Toe-off: The instant of when the toe of the trailing foot leaves the ground to begin swing phase during a gait cycle.

U

Unreal: A video game that has a gaming engine where you can create your own modifications.

V

Valve: A video game developing company who made the Halflife 2 and Counterstrike games.
Vicon: An optical motion capture system.
Video Game: An animated interactive form of entertainment playable on a computer, a game console or a hand held device.
Virtual Reality: A computer generated interactive scenario developed to simulate real circumstances.
VR: Short for virtual reality.

W

Walk Cycle: The animated action of walking. Walk cycles can exhibit characteristics such as gender or moods.
World Coordinate System: The global coordinate system that never moves. It is the origin from which all world data is measured. It’s the same as the global coordinate system.

X

X Axis: The axis that extends forward from the body of the ShapeRecorder character.

Y

Y Axis: The axis that extends upward through the body of the ShapeRecorder character.
Yaw: Rotations about the Y axis when the Y axis extends upward through the body.

Z

Z Axis: The axis that extends laterally from the body of the ShapeRecorder character. Its direction follows the right hand rule.

Other Motion Capture Resources

Motion Capture History

Motion Capture Hardware

Motion Capture Software

Motion Capture Process

Motion Capture Videos

Motion Capture Books and Magazines