Research Article
Research on Shape Feature Recognition of
B-Rep Model Based on Wavelet Transform
Jihua Wang
College of Information Science and Engineering, Shandong Normal University, No. 88 Wenhua East Road, Jinan 250014, China
Correspondence should be addressed to Jihua Wang; jihuaaw@.com
Received 11 January 2018; Accepted 12 July 2018; Published 19 July 2018
A
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ademic Editor: Erik Cuevas
Copyright © Jihua Wang. is is an open access article distributed under the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
B-Rep (Boundary Representation) CAD model is widely used in the representation of manufactured product in computer, and it is
a kind of real D structure with invisible part relative to .D mesh model, so the shape feature recognition of B-Rep model is worth
of much studying. We present one approach of shape feature recognition of B-Rep model based on the wavelet transform of surface
boundary and region; it is inspired by the neuropsychology view that surface is the key visual features and by the systematology
method that an object is recognized by decomposing and grouping its similar parts. Surface elements of B-Rep model are extracted
from the neutral STEP (Standard for Exchange of Product Model Data) le; the curvatures of surface boundary and region were
decomposed by wavelet transform, and then the coecient statistics of same scale were as the surface feature vector. Similar surfaces
ofB-Repmodelwereclusteredasabinwiththesumofperimetersandthemeanvector,andallbinsconstitutingahistogram
are nally as the feature vector of B-Rep model. us B-Rep models are compared and retrieved using the EMD (Earth Mover’s
Distance) of histogram. Our approach was evaluated by retrieval experiment with NDR (National Design Reservoir), and the result
indicated its highly competent performance.
1. Introduction
Shape feature recognition of CAD model lays the solid
foundation for content-based model retrieval, functions and
structures mapping, design intent analysis throughout indus-
trial product design, and manufacture eld. B-Rep model
is almost only representation way of CAD model related to
manufactured objects, which is widely shared and exchanged
in STEP format. Comparing with the mesh model as .D
model that only gives us overall visible appearance, B-Rep
modelasrealDmodelhasunambiguousinternalschemes
and contains rich design semantics such as geometric and
topology variables, and it can be precisely expressed in the
form of attributed adjacency graph (AAG) [, ]. B-Rep model
shows its structures and characteristics by mathematical
language in computer, but it does not directly provide us with
recognition features. erefore it is meaningful to extract the
shape features of B-Rep model for supporting recognition,
classication, and retrieval, even transforming B-Rep model
into high-level knowledge representation from low-level
geometry descriptor [].
B-Rep model is designed and stored in proprietary
format in dierent CAD platform and transformed into a
neutral STEP le for transferring, sharing, exchanging, and
displaying in heterogeneous CAD environments. Under the
guidance of STEP as an international standard, the dierent
modeling methods result in almost the same STEP les. B-
Rep model in STEP format is a hierarchy with geometric
and topological elements of solid, shell, surface, loop, and
edge.
Surfaces are as the key elements of B-Rep model in the
paper. e view is attributed to the following facts. Firstly,
surfaces are the nodes in AAG which is commonly used
to express the topological and geometrical information of
B-Rep model completely, and the type of large surface has
the geometric even functional semantics. Secondly, surfaces
are the primary factors of D objects from a psychological
point of view. D shapes are spatial congurations of surface
fragments encoded by IT neurons []. Gibson thought that
the composition and layout of surfaces constitute what the
values and meanings of things in the environment aord [].
Gestalt psychologists try to settle how local discontinuities
Hindawi
Mathematical Problems in Engineering
Volume 2018, Article ID 6310482, 8 pages
https://doi.org/10.1155/2018/6310482