Page 162 - Anthropometry, Apparel Sizing and Design

Full body 3-D scanners 157

redundant points, and overlapping data will often not be aligned entirely with the sur-
face. If only the outermost points are retained, the model is likely to be too big, and if
only the inner points are retained, it is likely to be too small. Determining the optimal
choice that retains only those points that represent the actual surface of the body is
important. However, depending on the use to be made of the scan and the amount
of variation of the scan data, the redundant and overlapping points may not be a prob-
lem. If the main goal of the study is to generate automated measurements then the
measuring algorithm can be designed to take measurements appropriately in the data
cloud (Fig. 6.9).
Some scanners only capture data from the front and back of the body and generate
the missing parts of the scan on the relatively featureless side of the body. This can
work well for a population that does not have much variation, but particularly for a
population that has overweight or obese subjects, this can miss useful details of the
side of the body. Whether this is a problem will again depend on what the goals of
the research. It is not necessary to capture every detail of the body shape for some
studies.
If the goal is to derive cross-sectional data, or to manually measure scans, or to 3-D
print the scans, or to create a digital avatar, then it is often necessary to merge the data
into a single shell, to reduce the number of redundant points and to make a
“watertight” model by filling in missing data. In the early days of body scanning, this
was done using 3-D software designed for engineering uses, such as PolyWorks,
which was not very effective at manipulating organic shapes, but current software
designed to manipulate 3-D data makes these tasks much easier. Some software sys-
tems for 3-D manipulation are only designed to work with NURBS models and there-
fore need to be converted from the XYZ coordinate points generated by the body

Fig. 6.9 Representations of circumferential measurements taken on a slice from a scan that has
not been merged to delete redundant points. The measurement can be taken through the points
on a path that averages the variation or outside all the points. The second method will give a
slightly larger value.