Types of MoCap
Motion capture is typically accomplished by any of the following Methods while each technology has its strengths and weakness, there is not a single motion capture technology that is perfect for every possible use.
Magnetic motion capture system is utilization of sensor on body. These sensors are cabled to electronic control unit that correlates their reported locations within the field. These electronic controlled unit are networked with the host computer that uses a software driver to represent these positions in 3D space. These sensors denotes the positional and rotational information of markers
Pro: Real time, No correspondences, smaller workspace, positions are absolute, rotations are measure absolutely, relatively cheaper than optical
Cons: Heavier sponsors, difficult to move, wires on body, Cost, Limited Range, magnetic distortion occurs as distance increases, prone to interference from magnetic fields- cement floors usually contain metal, so stages must be built
In this type of motion capture Performer wears a human shape set of metal strips like a very basic skeleton that is hooked on to performers back. Each joints has sensors which gives the position.
Other type of mechanical motion capture involves gloves, mechanical arm, or articulated models (like monkey), which are used for key framing.
Pro: no interference from light or magnetic fields, No range limit, n
Con: No realistic motion. Sensors makes noise. The technology has no awareness of ground, so there can be no jumping, plus feet data tends to slide. Equipment must be calibrated often. Unless there is some other type of sensor in place, it does not know which way the performer’s body is pointing. Absolute positions are not known but are calculated from the rotations.
Optical motion capture is most commonly used technology. There are two types of optical motion capture. Reflective and Pulse LED. Optical motion capture is capturing data digitally which is capable of turning real life motion into digital form. Optical motion capture is extensively used many fields like animation, special effects, gaming. This technique brings a better feeling of life in character.
In short it uses number of special cameras from different angle. Basically using two or more camera angles brings a sense of a 3d world. This technique has reflective markers which are placed on actor’s body. Because these are reflective markers, it becomes easy for software to identify the position in 3d world. When the same marker gets tracked from more than one camera it gives details of all the three axis. Marker base capture can give more accuracy over mark less motion capture.
Pro: actors feel free to act as the suit isn’t heavy and the markers are lite, can work in large area, at a time more performances are possible, clean, neat and detailed data is captured.
Cons: expensive, markers can get hidden by other props or actors, prone to light interference