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10
Can Machines Interpret Line Drawings?
, 2004
"... Engineering design would be easier if a computer could interpret initial concept drawings. We outline an approach for automated interpretation of line drawings of polyhedra, and summarise what is already possible, what developments can be expected in the near future, and which areas remain problemat ..."
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Engineering design would be easier if a computer could interpret initial concept drawings. We outline an approach for automated interpretation of line drawings of polyhedra, and summarise what is already possible, what developments can be expected in the near future, and which areas remain problematic. We illustrate this with particular reference to our own system, RIBALD, summarising the published state of the art, and discussing recent unpublished improvements to RIBALD. In general, successful interpretation depends on two factors: the number of lines, and whether or not the drawing can be classified as a member of special shape class (e.g. an extrusion or normalon). The stateoftheart achieves correct interpretation of extrusions of any size and most normalons of 20–30 lines, but drawings of only 10–20 lines can be problematic for unclassified objects. Despite successes, there are cases where the desired interpretation is obvious to a human but cannot be determined by currentlyavailable algorithms. We give examples both of our successes and of typical cases where human skill cannot be replicated.
Local topological beautification of reverse engineered models
 ComputerAided Design
, 2004
"... Boundary representation models reconstructed from 3D range data suffer from various inaccuracies caused by noise in the data and by numerical errors in the model building software. The quality of such models can be improved in a beautification step, where geometric regularities need to be detected a ..."
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Cited by 3 (2 self)
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Boundary representation models reconstructed from 3D range data suffer from various inaccuracies caused by noise in the data and by numerical errors in the model building software. The quality of such models can be improved in a beautification step, where geometric regularities need to be detected and imposed on the model, and defects requiring topological change need to be corrected. This paper considers changes to the topology such as the removal of short edges, small faces and sliver faces, filling of holes in the surface of the model (arising due to missing data), adjusting pinched faces, etc. A practical algorithm for detecting and correcting such problems is presented. Analysis of the algorithm and experimental results show that the algorithm is able to quickly provide the desired changes. Most of the time required for topological beautification is spent on adjusting the geometry to agree with the new topology.
Detecting approximate symmetries of discrete point subsets
, 2008
"... Detecting approximate symmetries of parts of a model is important when attempting to determine the geometrical design intent of approximate boundaryrepresentation (Brep) solid models produced e.g. by reverse engineering systems. For example, such detected symmetries may be enforced exactly on the ..."
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Cited by 3 (2 self)
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Detecting approximate symmetries of parts of a model is important when attempting to determine the geometrical design intent of approximate boundaryrepresentation (Brep) solid models produced e.g. by reverse engineering systems. For example, such detected symmetries may be enforced exactly on the model to improve its shape, to simplify its analysis, or to constrain it during editing. We give an algorithm to detect local approximate symmetries in a discrete point set derived from a Brep model: the output comprises the model’s potential local symmetries at various automatically detected tolerance levels. Nontrivial symmetries of subsets of the point set are found as unambiguous permutation cycles, i.e. vertices of an approximately regular polygon or an antiprism, which are sufficiently separate from other points in the point set. The symmetries are detected using a rigorous, tolerancecontrolled, incremental approach, which expands symmetry seed sets by one point at a time. Our symmetry cycle detection approach only depends on interpoint distances. The algorithm takes time O(n 4) where n is the number of input points. Results produced by our algorithm are demonstrated using a variety of examples.
CAD/CAM Methods for Reverse Engineering: A Case Study of Reengineering Jewelry
 ComputerAided Design & Applications
"... Reverse engineering is the process of obtaining a geometric CAD model from 3D points acquired by scanning an existing physical model. It is widely used in numerous applications, such as manufacturing, industrial design and jewelry design and reproduction. We argue that for creating editable CAD mode ..."
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Reverse engineering is the process of obtaining a geometric CAD model from 3D points acquired by scanning an existing physical model. It is widely used in numerous applications, such as manufacturing, industrial design and jewelry design and reproduction. We argue that for creating editable CAD models meant for manufacturing it is more appropriate to use featurebased constraintbased representations, since they capture design intent. We provide a framework for reverse engineering of small objects and in particular jewelry that combines cross section identification, feature and constraint information exploitation to attain robust, accurate and editable CAD models. First, we extract certain candidate features for describing our point cloud. These features are then reconstructed to describe the solid object. Constraints are automatically detected and maintained. Constraints capture design intent and provide robustness guaranties. Voxel inspired techniques are also employed to describe repeated patterns common to various types of traditional jewelry.
Perpendicularity as a Key to Interpreting Line Drawings of Engineering Objects
"... Many recent approaches to the problem of interpreting line drawings as solid objects treat inflation as a twostage approach, the first stage being to produce a quick initial estimate of vertex zcoordinates, and the second being to refine these initial estimates to produce a "more beautiful" geomet ..."
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Cited by 3 (3 self)
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Many recent approaches to the problem of interpreting line drawings as solid objects treat inflation as a twostage approach, the first stage being to produce a quick initial estimate of vertex zcoordinates, and the second being to refine these initial estimates to produce a "more beautiful" geometry. By making
Advances in the Field of Reverse Engineering
"... This paper presents an overview of advances in the field of reverse engineering over the last 25 years. Initially, several basic definitions and terminology will be reviewed, followed by a discussion of how and why the foundational technology (both hardware and software) has developed. This will be ..."
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This paper presents an overview of advances in the field of reverse engineering over the last 25 years. Initially, several basic definitions and terminology will be reviewed, followed by a discussion of how and why the foundational technology (both hardware and software) has developed. This will be examined from both a driving research and market demand perspective. The evolution of hardware, such as detectors, cameras, optics and sources will be discussed with particular emphasis on landmark developments that transformed the field. Significant advances in the methodologies and algorithms underlying software tools will also reviewed. A look at the latest developments and achievements in reverse engineering techniques shows the incorporation of knowledge based and CAD driven approaches. The paper will conclude with several stateoftheart reverse engineering case studies from the fields of computer arts, medicine, dentistry, product development, manufacturing and virtual heritage. The authors consider the many possible future directions and applications of this field.
Detecting Approximate Incomplete Symmetries in Discrete Point Sets
 ACM Symp. Solid and Physical Modeling
, 2007
"... Motivated by the need to detect design intent in approximate boundary representation models, we give an algorithm to detect incomplete symmetries of discrete points, giving the models ’ potential local symmetries at various automatically detected tolerances. Here, incomplete symmetry is defined as a ..."
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Motivated by the need to detect design intent in approximate boundary representation models, we give an algorithm to detect incomplete symmetries of discrete points, giving the models ’ potential local symmetries at various automatically detected tolerances. Here, incomplete symmetry is defined as a set of incomplete cycles which are constructed by, e.g., a set of consecutive vertices of an approximately regular polygon, induced by a single isometry. All seven 3D elementary isometries are considered for symmetry detection. Incomplete cycles are first found using a tolerancecontrolled point expansion approach. Subsequently, these cycles are clustered for incomplete symmetry detection. The resulting clusters have welldefined, unambiguous approximate symmetries suitable for design intent detection, as demonstrated experimentally.
Creating Editable 3D CAD Models from Point Cloud Slices
"... We introduce a novel approach to reconstructing 3D objects from cross sections of point clouds acquired by laser scanning. Cross sections are almost planar clusters of 3D points. We first thin each cluster to obtain an ordered one dimensional set of points. We then partition the point set to subsets ..."
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We introduce a novel approach to reconstructing 3D objects from cross sections of point clouds acquired by laser scanning. Cross sections are almost planar clusters of 3D points. We first thin each cluster to obtain an ordered one dimensional set of points. We then partition the point set to subsets that can be approximated adequately by piecewise quadratic or cubic rational Bezier curves using an optimal fitting method. For each curve we select a number of representative points that lie on the fitting curves which are then used for reconstructing the object surface. Intercross section and intracross section constraints are imposed to support parameterization and editing of the derived model. Shape and topological differences between adjacent object contours cause severe difficulties in the 3D reconstruction process. By using the contour skeleton information we create intermediate slices representing places where ramifications occur to achieve robust covering (meshing) of adjacent slices.
www.elsevier.com/locate/cad Detecting approximate symmetries of discrete point subsets ✩
, 2006
"... Detecting approximate symmetries of parts of a model is important when attempting to determine the geometrical design intent of approximate boundaryrepresentation (Brep) solid models produced e.g. by reverse engineering systems. For example, such detected symmetries may be enforced exactly on the ..."
Abstract
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Detecting approximate symmetries of parts of a model is important when attempting to determine the geometrical design intent of approximate boundaryrepresentation (Brep) solid models produced e.g. by reverse engineering systems. For example, such detected symmetries may be enforced exactly on the model to improve its shape, to simplify its analysis, or to constrain it during editing. We give an algorithm to detect local approximate symmetries in a discrete point set derived from a Brep model: the output comprises the model’s potential local symmetries at various automatically detected tolerance levels. Nontrivial symmetries of subsets of the point set are found as unambiguous permutation cycles, i.e. vertices of an approximately regular polygon or an antiprism, which are sufficiently separate from other points in the point set. The symmetries are detected using a rigorous, tolerancecontrolled, incremental approach, which expands symmetry seed sets by one point at a time. Our symmetry cycle detection approach only depends on interpoint distances. The algorithm takes time O(n 4) where n is the number of input points. Results produced by our algorithm are demonstrated using a variety of examples.
EUROGRAPHICS Workshop on SketchBased Interfaces and Modeling (2009) C.Grimm and J.J. LaViola Jr. (Editors) Towards Beautification of Freehand Sketches using Suggestions
"... Beautification of freehand sketches is integral for building robust sketch understanding systems and sketchbased interfaces for CAD. Many of the current methods for beautification do not consider some important information implied in the sketches such as spatial relationships (geometric constraints ..."
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Beautification of freehand sketches is integral for building robust sketch understanding systems and sketchbased interfaces for CAD. Many of the current methods for beautification do not consider some important information implied in the sketches such as spatial relationships (geometric constraints) between primitives. In addition, as the freehand input is ambiguous in nature, correctly interpreting the visual scene the user has in mind is a difficult problem. To this extent, we present our ongoing work, a suggestive interface for constraintdriven beautification of freehand sketches which provides multiple interpretations of the freehand input, from which the user can choose the intended result. A preliminary user study has been conducted to evaluate the effectiveness of the proposed method.