View Full Version : Digitizing marker locations in 3D cinematography.

Jonathan Merritt
04-06-2002, 02:17 PM
Hello Everyone,

I am currently researching the basics of 3D cinematography systems that
use retroreflective markers. My eventual aim is to write some software
that can take scanned film images from a set of cameras and produce a
set of 3D coordinates for the markers.

Presently, I am looking for methods by which markers may be digitized
automatically in two-dimensions from film frame images. I am aware that
one method by which markers are digitized is simply for an operator to
view each frame of a motion-capture session and manually tag the marker
locations with a cursor. However, I have also come across automatic
digitizing methods which are advertised as part of commercial gait
analysis systems. So far, I have not been able to find a good reference
for how these automatic systems work. I have searched the ISB software
pages, the BIOMECH-L archives and the internet. However, I am slightly
unsure about which field encompasses this question and what keywords I
should be using.

Intuition says that it should be possible to use some sort of
thresholding or watershed algorithm to find marker locations, using the
calculated centroid of the marker as "the location" (and what I have
found so far hints at this). Does anyone know of any good papers on
this subject, or what keywords I should be using in order to find them?

Many thanks, :-)

Jonathan Merritt, PhD Student.
Equine Clinical Research Unit,
Faculty of Veterinary Science,
The University of Melbourne.

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