Tech Briefs Magazine - May 2022 - PIT-13

Massey, with a wide array of experience in
the details of how motion capture worked
in practice, not just in theory. They were
a group who knew how we could help
make sense of this problem in a way that
would be useful and informative for our
audience.
Over a period of months, we reviewed a
range of external methods, trying some of
the most promising, to assess their effectiveness
and relevance to how the systems
were being used. We decided that a method
developed and assessed by the subcommittee
for 3D measurement systems
at the American Society for Testing and
Materials (ASTM E57) was most appropriate.
ASTM established the E57 committee
in June 2006 specifically to develop standards
that could be used to evaluate the
performance of 3D systems. The method
E3064 ( " Standard Test Method for Evaluating
the Performance of Optical Tracking
Systems that Measure Six Degrees of
Freedom (6DOF) Pose " ) is a simple one
that allows a uniform measurement between
two rigid objects while moving in a
controlled way in an optical motion capture
volume.
This method has the advantage of being
simple to understand and explain. But it
also has the benefit of assessing a continuously
moving object (a critical component
of a motion capture system, and a variable
that can make a significant difference)
and assessing errors quickly in many locations
within the capture volume.
It's important, though, to mention that
there is no 'correct' method. There are
also many different alternatives, and each
method has different merits. However, it
was felt that this was an informative method
to help explain to people the type of
performance they may be able to expect
with an assessment that was relevant to
how Vicon systems are used by engineers.
We tested two separate but similar setups,
made up of Vantage 5 MP or 16 MP
cameras, and measured the distance between
two rigid objects. This was a known
fixed distance that was constructed of
thermally neutral plastic to eliminate, as
much as possible, physical differences that
might arise from movement or temperature
changes. This enabled the measurement
accuracy to be determined consistently
against this known fixed reference
as it moved around the volume, as well as
enabling accurate assessment of the meaPhotonics
& Imaging Technology, May 2022
Free Info at http://info.hotims.com/82321-741
13
surements. Observation was consistent
even though the object was moved across
the capture volume and in continuous
motion.
This work now enables us to better
communicate how new developments
improve the quality that Vicon provides.
A good example of this is the recent rePIT
Spectrogon Ad 0522.qxp_1/2 Page Island 4/14/22 2:45 PM Page 1
lease of Vantage+ where we're now able to
clearly explain not only the benefits that
increased frame rates can deliver, but also
the inherent trade-offs that exist within
the technology.
This article was written by Dr. Felix Tsui, Product
Manager, Vicon (Oxford, UK). For more information,
visit http://info.hotims.com/82321-225.
PIT Tech Leaders Vicon Feature 0522_2.indd 13
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4/18/22 12:58 PM
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Tech Briefs Magazine - May 2022

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