Establishment of Digital Human Head Model Coordinate System Based
on Mean Curvature Analysis
Qiang Han
1, a
, Jianfei Ouyang*
1, b
, Xiang Ma
1, c
and Yonggang Yan
1, d
1
State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University,
Tianjin, 300072, CHINA
a
qianghan625@gmail.com,
b
oyj@tju.edu.cn,
c
xiangz.gm@gmail.com,
d
tjzyan@gmail.com
Keywords:
modeling; mean curvature; feature point; measurement techniques.
Abstract. The human body model scanned by a structured light scanner is based on the scan
coordinate system. Since the structured light scanner is not fixed, when the scanner scanning human
body in different position, we can get several models, the coordinates of the same point on these
models are not the same. In order to solve this problem, we propose a method. We extract facial
feature points with the use of mean curvature analysis. The feature points are used to determine the
digital human head model coordinate system. We can convert the human head models from the scan
coordinate system to the digital human head model coordinate system. After the conversion, the
coordinates of a same point on different models are approximately the same, which can make the use
of scanner more efficiency and user-friendliness.
Introduction
Digital human modeling is a technique which combines 3D visualization techniques with
anthropometry, by reconstructing human visual models and using data processing algorithms to
get the accurate size of many parts of the body.
Structured light scanning technology has many advantages. Its easy operation, high speed, high
precision, wide range, has been used in digital human modeling to achieve good results [1]. The
human body model scanned by a structured light scanner is based on the scan coordinate system.
Since the scanner is not fixed, when it scans the human body from different positions, we can get
several models from different frames of reference with different coordinates for a single point on the
body. Practically, this phenomenon can be very inconvenient, and thus it is necessary to create a
coordinate system that is fixed and unique in the human body, and convert the models from the scan
coordinate system to the above coordinate system.
This paper describes a method to create a digital human head model coordinate system which can
ensure that the coordinate system is fixed and unique in the human body. We also provide a method
to find the relationship between scan coordinate system and digital human head model coordinate
system.
Principle of the establishment of the coordinate system
Facial feature points extraction based on the mean curvature analysis. Curvature measures how
fast a curve is changing direction at a given point. Curvature can be used to extract feature
points[2,3]
.
Let p be a point on facial surface S. Consider all curves C
i
through p on S, where
each C
i
corresponds to a curvature K
i
at point p. There are at least a maximum curvature K
1
and a
minimum curvature K
2
among these curvature K
i
. The two curvatures K
1
, K
2
called as the principal
curvatures of S. The mean curvature H of point p is the average of the two principal curvatures,as
Eq. 1 shows:
H=0.5(K
1
+K
2
). (1)
Mean curvature reflects the characteristics of the concaves and convexes of the facial surface,
which can be used to identify prominent features of the face (eye socket, nose, lip, and ear) [4,5]. The
mean curvature values showed a certain degree of aggregation. It is easy to separate them from
Applied Mechanics and Materials Vols. 239-240 (2013) pp 703-707
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.239-240.703
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
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