A COMPARISON AND EVALUATION OF MOTION INDEXING ...

(b) Active markers: Markers have one or multiple LEDs which are illuminated
timely to identify them by their relative positions.
(c) Time modulated active markers: Markers are same as in active marker
system but are strobed one at a time.
(d) Semi Passive imperceptible markers: Makers use photosensitive marker
tags to decode the optical signals. These tags can compute not only loca-
tions of each point, but also their orientation, incident illumination, and
reflectance.
Optical systems have become quite popular over the last couple of years. The
data obtained is very detailed. These systems provide the most freedom of
movement to the subject as they do not require any cabling. The problem with
optical systems is that a subject can easily occlude, or hide, one or more markers
which can create ”holes” in the data stream. This is sometimes reduced by
adding more cameras but it also makes the tracking of the markers complicated
and increases execution time. Increasing markers is not a good solution as it
introduces confusion in the capture.
Markerless motion capture is an advancement in optical motion capture systems.
They do not require subjects to wear equipment. Special computer algorithms
are designed to allow the system to analyze multiple streams of optical input and
identify human shapes, breaking them down into constituent parts for tracking.
B.2.1 Why Motion Capture is required?
Motion Capture can be refered as the 3D representation of a live performance of
an actor. No matter how different an actor or object look in the simulated 3D world
after motion capture, it will resemble complete physical and emotional performance.
This property of motion capture makes it useful for many applications in many dif-
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