Motion Capture Technology: Shapetapetm

By: A. Lowery

ShapeTapesTM are long Tapes of fiber-optic bend / twist sensors that give the Tape the ability to measure 3D position and orientation. ShapeTapesTM are the primary hardware for the ShapeWrap IITM Motion Capture System. Measurand Inc. in New Brunswick, Canada develops ShapeTapeTM.

Types of Motion Capture Systems
Optical: Optical motion capture systems use cameras to track markers on a moving body. Generally these are the most accurate motion capture systems.

Magnetic: Magnetic motion capture systems have magnetic markers that are tracked in a magnetic field to capture the motion of a moving body.

Mechanical: Mechanical motion capture systems use a variety of orientation sensors, bend sensors and potentiometers to track motion. ShapeTapeTM is considered a mechanical motion capture device.

ShapeTapeTM Basics
ShapeTapesTM are made by placing several loops of fiber optics along the length of a flexible substrate. The individual loops are treated in such a way that when the Tape is manipulated the changes in light passing through the fiber optic will represent a bend or twist. An Interface Box reads the changes in light and outputs a voltage signal. This voltage signal is the input to the ShapeTapeTM's software.

ShapeTapeTM Software
ShapeWrap IITM operates with software called ShapeRecorderTM. ShapeRecorderTM provides a 3D representation of the subject's motions in real time. The motions can be recorded and then converted into a variety of different data formats including BVH, C3D, and Global Position and Orientation.

Benefits of ShapeTapeTM
Unlike optical or magnetic motion capture systems, ShapeTapeTM does not require external devices to capture the motion. Thus, no extra studio space is required for cameras or magnetic detectors etc... ShapeTapeTM does not require markers so there is no danger of marker occlusion or marker swapping. ShapeTapeTM can operate wirelessly at over 100 m from the computer running ShapeRecorderTM. The ShapeWrap IITM Motion Capture System is popular with animation schools and performing arts schools because of its portability and user-friendly nature. ShapeWrap IITM is also one of the most affordable motion capture systems in the market.

Disadvantages of ShapeTapeTM
ShapeTapeTM is accurate to 1 mm per 1000 mm length of Tape. Although this is more than enough for many motion capture applications, some consumers require the sub-millimeter accuracy of an optical motion capture system. The ShapeWrap IITM Motion Capture System has a robust design that accommodates rough use, however since the ShapeTape are worn on the body the most aggressive moves may cause some artifacts in the data.

More Information on ShapeTapeTM
Details on ShapeTapeTM and ShapeWrap IITM can be found on Measurand Inc.'s website, http://www.motioncapturesystems.com

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