A Line Drawing Method of the 3D Models
Based on Partial Sharpening
Qiuqing Meng, Guohua Geng, and Jing Zhang
Institute of Visualization Technology, Northwest University, Xi’an, China
Email: mqq_1024@126.com and ghgeng@nwu.edu.cn
Abstract—This paper aims to propose an automatic line
drawing method of the 3D models that is used for the
archaeological drawing field. This method begins with
partial sharpening of the triangular mesh model
according to the characteristics of local curvature. Then
the line drawings of the triangular mesh model would be
achieved by extracting features of the model and
generating the contour lines. After experiments, it testifies
that this method can not only draw more details, but also
obtain preferable drawing effects of triangular mesh
model with rich noises, and the results are accurate.
Undoubtedly, this method has practical significance for
archaeologists to reduce the workload and improve the
efficiency of archaeological drawings.
Keywords—3D model; archaeological line drawing; partial
sharpening; feature line extraction
I. INTRODUCTION
As an important basic work for the conservation and
restoration of cultural relics, archaeological drawings
are still mainly drawn by manual labor. In manual
measurement, the whole process includes many
complex steps, and the rendering speed is too slow, the
accuracy of graphics is not good and the graphics
quality varies from person to person. These factors
limited the further development of archaeological work
and research for a very long time.
With the rapid development of information
technology, especially the development of 3D laser
scanning modeling technology, computer graphics,
virtual reality and other technologies, some new
techniques have been widely used in archaeological
works, which greatly promoted the development of
archaeology. Instead of manual measurement, modern
mapping technology has achieved considerable
progress with these new techniques; close-range
photogrammetry, aerial photogrammetry, conventional
geodetic surveying, digital orthophoto method and
digital drafting technology entered the field of
archaeological drawing. After the 1990s, the rapid
development of Non-Photorealistic Rendering brought
new hope to change the archaeological drawing work
mode. Many algorithms were proposed, and the
purpose is to automatically generate archaeological line
drawings by computer to replace the original manual
operation form.
Contours rendering of a 3D model is the basis for
line drawing rendering technology. The contours of a
3D model can be classified into two categories [1]
dependent on the line of sight: the contours based on
view-dependent and the contours based on view-
independent. The contours based on view-dependent
means we should determine the viewpoint before
extracting such contours; they are dependent on the
viewpoint. The representative methods for this category
are Suggestive Contours proposed by Decarlo and
others [2], and the Apparent Ridges proposed by Judd
and others [3]. The contours based on view-independent
means the extracted contours are related to the
geometrical characteristic of the 3D model itself; they
are not dependent on the viewpoint. These kinds of
contours includes creases, valleys and ridges [4].
Demarcation Curves proposed by Kolomenkin and
others [5] can effectively depict the texture information
of a cultural relics model, and is suitable for
archaeological illustrations of cultural relics. Jing Hao,
et al [6] combined with the above methods, proposed a
3D model feature-line extraction method using mesh
sharpening; this method sharpens the model as a
pretreatment operation, then recalculates the 3D model
vertex coordinates, not only to get more details, but also
to reduce the related calculation of the model curvature.
II. O
VERVIEW OF THE LINE DRAWING METHOD
On the basis of the existing algorithms, this paper
aims to propose an automatic line drawing method of
3D models based on partial sharpening. This method is
mainly divided into two parts: determining the
sharpening areas and feature line drawing.
A. Determine the Sharpening Areas
First, estimate the discrete curvature of each vertex,
then the model is divided into flat areas and feature
areas according to the curvature of the model. The
feature areas are the sharpening areas.
B. Feature Line Drawing
Sharpen the feature areas, and recalculate the
vertices’ coordinates, which belong to the feature areas.
Then we extract and draw the feature lines of the
triangular mesh model. Finally, output the line drawing
of the 3D model.
This method can be used to select the sharpening
areas automatically and it avoids noise interference on
the feature line extraction effectively. The experimental