Page 163 - Anthropometry, Apparel Sizing and Design

158 Anthropometry, Apparel Sizing and Design

scanner. Nonuniform rational B-spline (NURBS) models are based on mathematically
generated curves and surfaces. Such models can be modified more easily than 3-D
coordinate models by moving specific control points. NURBS models are more com-
monly used for geometric shapes; the complex organic shape of the human body is
more difficult to represent and to modify using NURBS curves.

6.6 Automatic landmarking and data extraction software

The process of generating body dimensions automatically is distinct from the process
of creating a 3-D digital body. Most scanner systems have the ability to automatically
derive linear measurements from the scan, but the algorithms used by different scan-
ner companies vary. The scanner that generates the best scan for a project may not
have the best automatic measuring system for that project. Most scanners can accept
a scan in a generic format made by a different scanner, so it is possible to scan in one
system and derive measurements in another.
The first step in generating a measurement from a scan is to identify the points on
the body to be measured, the body landmarks. These landmarks are well defined by
anthropometrists (Hotzman et al., 2011), tailors (Roetzel and Fritz, 2014), and apparel
practitioners ( Joseph-Armstrong et al., 2010), though each group has different sets of
landmarks, different placement of landmarks, and different methods of measuring
between landmarks. Because there is great variation among body shapes, it can be
very difficult to place landmarks reliably, and although a trained anthropometrist will
generally place landmarks more reliably, some variation will always be present
(Kouchi and Mochimaru, 2011). It is even more difficult to design software to reliably
place landmarks on body scans. This is generally done by programming a search for
certain geometric features on the body (Suikerbuik et al., 2004), but programming for
every possible body configuration can be almost impossible, particularly given the
variation of shape between underweight and overweight bodies.
Because clothing is designed to move with the body, many of the critical landmarks
that define measurements are where the body articulates—the joints. Therefore land-
marks are often placed by anthropometrists and apparel practitioners by palpating to
feel the appropriate bony protuberances that define the center of joint movement
(Fig. 6.10). It is not possible for the scan software to achieve the same level of pre-
cision and reliability by judging landmarks on joints based on the surface geometry of
the body.
Other landmarks are established by common practice in the apparel industry or dic-
tated by clothing styles. Placement of the landmark to measure waist circumference is
a good example of this (Wren et al., 2014). The “natural” waist can be identified as the
level of the spine of greatest articulation, between L4 and L5 of the lumbar vertebrae,
or at the omphalion (belly button), or in normal weight women at the point where the
body curves in the most at the side. In some body shapes, this area where the body
curves in and makes a natural ledge is parallel to the floor, but in others, it tips down
in front. On the other hand, most men have a small (or when less athletic, a substantial)
bulge at the level of greatest articulation. However, none of this is helpful as currently