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Detail‐feature‐preserving surface reconstruction
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In this paper, we propose a feature-preserving surface reconstruction method from sparse noisy 3D measurements such as range scanning or passive multiview stereo. In contrast to earlier methods, we define a novel type of explicit 3D filter—regularized weighted least squares filter—to characterize the detail features such as surface wrinkles and sharp<br> features. To account for noise, we rasterize input-oriented points into a probabilistic volume (base volume) and then create a gu
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COMPUTER ANIMATION AND VIRTUAL WORLDS
Comp. Anim. Virtual Worlds
2012; 23:407–416
Published online 24 May 2012 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/cav.1464
SPECIAL ISSUE PAPER
Detail-feature-preserving surface reconstruction
Xu Zhao
1
, Zhong Zhou
1
*,YeDuan
2
and Wei Wu
1
1
State Key Laboratory of Virtual Reality Technology and Systems, School of Computer Science and Engineering, Beihang
University, Beijing, China
2
Computer Graphics and Image Understanding Lab, Department of Computer Science, University of Missouri – Columbia,
Columbia, MO, USA
ABSTRACT
In this paper, we propose a feature-preserving surface reconstruction method from sparse noisy 3D measurements such
as range scanning or passive multiview stereo. In contrast to earlier methods, we define a novel type of explicit 3D
filter—regularized weighted least squares filter—to characterize the detail features such as surface wrinkles and sharp
features. To account for noise, we rasterize input-oriented points into a probabilistic volume (base volume) and then create
a guidance volume by Gaussian filtering. Both the base volume and the guidance volume are further filtered by regularized
weighted least squares filter to detect and recover detail features. After the two-stage filtering, a global minimal surface is
computed by graph cut and meshed as a geometric model. Experimental results on various datasets show that our method
is robust to noise, outliers, and missing parts, which makes it more suitable to fit indoor/outdoor multiview stereo data.
Unlike other methods, our method can completely recover scene structures and preserve detail features from noisy point
samples. Copyright © 2012 John Wiley & Sons, Ltd.
KEYWORDS
surface reconstruction; computational geometry; computer graphics
*Correspondence
Zhong Zhou, State Key Laboratory of Virtual Reality Technology and Systems, School of Computer Science and Engineering,
Beihang University, Beijing, China.
E-mail: zz@vrlab.buaa.edu.cn
1. INTRODUCTION
Reconstructing 3D surfaces from point samples is well
studied in many areas of computer graphics, including laser
scanning, reconstructing image-based surfaces, and repair-
ing of noisy meshes [1]. It focuses on approximately fitting
a surface to point samples, filling holes, or remeshing exist-
ing models with the use of information about the sampling
process, for example, bounds on the noise magnitude or the
sampling density.
There are many approaches for acquiring 3D shapes
from real-world objects, which can be basically classified
into two categories: active lighting systems and passive
stereo systems. Active lighting systems, such as laser-
based scanners, structured light scanners, and infrared
light devices, can produce more stable and accurate point
samples than passive stereo systems. Recently, however,
the passive stereo systems have become increasingly
popular for their low-cost acquiring devices and attrac-
tive indoor/outdoor applications [2,3]. Unfortunately, most
surface reconstruction algorithms cannot be directly used
for passive stereo systems. For example, in passive mul-
tiview stereo, reconstructed point samples are seriously
affected by insufficient images, illumination changes,
calibration errors, poor photo-consistent matches, and the
structure and appearance of the scene to be reconstructed.
Until recently, it has been a challenge to perform surface
fitting from such poor point samples.
The latest surface reconstruction algorithms, such as
Poisson surface [4] and touch expand [5], alleviate the poor
data fitting problem to some extent and are widely used in
image-based modeling systems. The key objective of these
two methods is to define a s urface-fit quality function from
oriented points and then solve this optimization function. It
is important to note that they all implicitly use a Gaussian
filter in their algorithms to avoid the influence of noise and
outliers and to achieve a smooth mesh model. They per-
form well in many cases especially when the surface of the
reconstructed object is inherently smooth. But the smooth
shape prior assumption also ignores some important detail
features such as surface wrinkles as well as sharp edges and
corners that occur widely in natural and artificial objects.
Meanwhile, when considering points obtained using multi-
view stereo, detail features are difficult to distinguish from
the noisy or incomplete point samples because both details
and noise are high-frequency s ignals.
Copyright © 2012 John Wiley & Sons, Ltd. 407
Detail-feature-preserving surface reconstruction X. Zhao
et al.
To solve these problems, we present a novel feature-
preserving filter called regularized weighted least squares
(RWLS) filter. The key idea is to define the detail
features as the covariances between the input and a
Gaussian-smoothed intermediate result. Also, a regulariza-
tion parameter is added into the kernel function to balance
the two. To account for noise, we first rasterize oriented
points into a probabilistic volume (also called base volume)
and create a guidance volume by Gaussian filtering. This
filtering is completed using a large filter radius to ensure
the reconstruction completeness and suppress noise as well
as details. Only the significant high-frequency features that
are defined as detail features are detected and recovered
during RWLS filtering. Finally, meshes are generated from
the filtered volume by graph cut.
The advantages of our method include the following: (1)
the method has the ability to recover both sharp features as
well as surface wrinkle features, and the level of detail can
be easily controlled by adjusting filter parameters; and (2)
the method is robust to noise, outliers, and missing parts,
which cannot only be used for range scan data fitting but is
also suitable for indoor/outdoor multiview data.
2. RELATED WORK
The earliest surface reconstruction methods are primar-
ily designed for fitting 3D laser scanner data. They can
be roughly classified into two major categories: implicit
surface methods and Delaunay-based methods.
The goal of implicit surface methods is to implicitly
define a level-set surface function such as signed distance
function [6], radial basis function [7], or moving least
squares (MLS) [8]. Among them, the MLS scheme can
approximate the local surface from the point set with a
moderate amount of noise, and various methods are fur-
ther developed to improve its stability [9] or preserve sharp
features [10]. However, they always fail when the points
are irregularly sampled (e.g., incomplete) or too noisy. The
idea behind MLS is to perform a local polynomial fitting
in weighted least squares (WLS) sense, which can also be
seen as an optimization-based filter kernel. Similarly, we
define an RWLS filter for surface reconstruction. However,
there are two differences in our method: (1) the filtering
process is computed in 3D probabilistic space; (2) a guid-
ance volume is generated by Gaussian filtering to suppress
more noise and ensure the reconstruction completeness.
Note that the 2D RWLS filter has been recently proposed in
an image processing area [11]. Its applications include haze
removal, image matting, high dynamic range (HDR) com-
pression, noise reduction, and others [12]. An extensive
literature search led to the conclusion that our method is
the first attempt to extend the filter to 3D digital geometry
processing, which led to its successful application in
detail-feature-preserving surface reconstruction.
Delaunay-based methods typically interpolate all or
most of the points on the basis of combinatorial structures,
such as Delaunay triangulations [13], alpha shapes [14],
or Voronoi diagrams [15]. More recent work focuses
on combining with other techniques such as partition-
ing strategy [16], variation method [17], or energy opti-
mization framework [18] to improve the robustness to
noise, outliers, and irregular sampling. Most notably,
Salman et al. [19] addressed the problem of generating
surface meshes from 3D point samples while preserving
sharp features. They explicitly extract sharp features on
the basis of the covariance matrices of Voronoi cells and
then perform a feature-preserving variant of a Delaunay
refinement process. However, most of these methods are
not designed for the passive stereo system.
For the problem of surface reconstruction from multi-
view stereo (MVS) point sets to be solved, shape priors
and probabilistic optimization framework are often used.
The basic shape prior assumes that the surface to be
reconstructed is smooth, which yields to a regularized
optimization problem [5,20]. Poisson surface [4] and
touch expand [5] are two typical surface reconstruction
algorithms and are widely applied in MVS reconstruction
for their robustness. Kazhdan et al. [4] aligned the gradient
of the indicator function with a vector field from the
input-oriented points and compute it as a Poisson problem.
Lempitsky and Boykov’s global optimization approach [5]
is based on the minimal surface framework with graph cuts
in [21] and expresses the generic surface-to-data fit quality
measurement as a flux-based function. Both methods
implicitly use the Gaussian filter to handle sample noise,
which is equivalent to the smoothness shape priors.
Nevertheless, in practice, we found that if the filter radius
is large, both implicit model and globalization methods
will obtain a complete but oversmooth model. However, if
the filter radius is small, a detailed but incorrect geometric
model is produced. In many cases, both the completeness
(scene structure) and surface details are crucial to the
perception of 3D models. However, it is hard to make a
trade off between them. Unlike these methods, our method
first creates a guidance volume by Gaussian filtering
and then recovers detail features by RWLS filtering. The
two-stage filtering ensures that the resulting model can
contain both complete structures and detail features.
Moreover, the RWLS filter parameters can be easily
adjusted to control the level of detail features to be
preserved. Recently, more shape priors such as planar
plane [22] and basic geometric shape primitives [23] are
introduced. However, these assumptions are more suitable
for urban scenes, whereas the local shape priors in RWLS
filter are adaptively determined within a given neighbor-
hood and have no limitation of scene types.
3. METHOD OVERVIEW
The overall goal of our method is to reconstruct a mesh
surface from well/poor-sampled oriented points, to ensure
the completeness and to recover detail features as much
as possible. Figure 1 illustrates the basic step-by-step pro-
cess of our surface reconstruction method, which consists
408
Comp. Anim. Virtual Worlds
2012; 23:407–416 © 2012 John Wiley & Sons, Ltd.
DOI: 10.1002/cav
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