An on-line copy of this file is available at http://pacvarley.110mb.com/Publications.html .
P. A. C. Varley Computer Modelling of Seasonal Storage of Solar Thermal Energy for District Heating Systems in the UK , MSc Dissertation, Department of Engineering, Cardiff University, 1995.
Abstract:
The performance of Solar-Aided District Heating Systems in the UK has been modelled using a simple one-dimensional heat storage model. Using this, a computer program to determine the optimum collector area and tank volume for a given capital cost has been developed.
Some suggested alternative system configurations have been investigated. The sensitivity of the results to various parameters of the model, both financial and technical, has been assessed. The most promising option appears to be a simple one-tank model with variable flow rate through the solar collectors and with a flow temperature to the district heating system of 70º to 75º. The effectiveness of such a system is improved if use can be made of water at temperatures below 45º, the normal minimum required for space heating and domestic hot water.
Two systems, one providing a 70% solar contribution and the other a 99% solar contribution, have been costed. The price of delivered heat is approximately £44 per MWh for the 70% system, £63 per MWh for the 99% system. This compares unfavourably with £26 per MWh for an oil-fired district heating system or £32 per MWh for single-house gas-fired heating, costed on the same basis. Variations in performance have little effect on these costs.
There are special circumstances in which the solar-aided system could be competitive. Some of these are discussed.
P. Varley, Techniques for Development of Safety-Related Software for Surgical Robots, IEEE Transactions on Information Technology in Biomedicine, 3(4), 261-267, 1999.
Abstract:
Regulatory bodies require evidence that software controlling potentially hazardous devices is developed to good manufacturing practices. Effective techniques used in other industries assume long timescales and high staffing levels and can be unsuitable for use without adaptation in developing electronic healthcare devices. This paper discusses a set of techniques used in practice to develop software for a particular innovative medical product, an endoscopic camera manipulator. These techniques include identification of potential hazards and tracing their mitigating factors through the project lifecycle.
P. A. C. Varley and R. R. Martin, A System for Constructing Boundary Representation Solid Models from a Two-Dimensional Sketch, Proc. Geometric Modeling and Processing 2000, Eds. R. Martin, W. Wang, 13-30, IEEE Computer Society Press, 2000. ISBN 0 7695 0562 7
Abstract:
This paper describes a system which converts a two-dimensional sketch with hidden lines removed of a single polyhedral object into a boundary representation solid model.
The system improves on a previous system by Grimstead by analysing the sketch for symmetry elements and regularities. It uses the results of this analysis to produce a more plausible topological completion of the hidden parts of the object, and to enforce exact constraints on the geometry of the boundary-representation model.
P. A. C. Varley and R. R. Martin, Constructing Boundary Representation Solid Models from a Two-Dimensional Sketch - Frontal Geometry and Sketch Categorisation, Proc. First UK-Korea Workshop on Geometric Modeling and Computer Graphics, 113-128, Kyung Moon Publishers, 2000. ISBN 89 7282 445 3
Abstract:
This paper discusses research results useful for producing a system which converts a two-dimensional computer sketch of a single homogeneous polyhedral object into a boundary representation solid model. An overview of our approach to such a system and its main algorithms is presented elsewhere.
This paper gives more detail of some of the algorithms for categorising sketches according to the type of object drawn and generating preliminary geometry for the part of the object visible in the sketch. It discusses various alternative methods considered and explains which were chosen and why. The topics covered in detail are parallel line detection, preliminary geometry, identification of symmetries and regularities, and sketch categorisation.
P. A. C. Varley and R. R. Martin, Constructing Boundary Representation Solid Models from a Two-Dimensional Sketch - Topology of Hidden Parts, Proc. First UK-Korea Workshop on Geometric Modeling and Computer Graphics, 129-144, Kyung Moon Publishers, 2000. ISBN 89 7282 445 3
Abstract:
This paper discusses research results useful for producing a system which converts a two-dimensional computer sketch of a single homogeneous polyhedral object into a boundary representation solid model. An overview of our approach to such a system and its main algorithms is presented elsewhere.
This paper gives more detail of our method for creating the topology of hidden parts, given a sketch for which the geometry has been given a preliminary interpretation, and the object has been assigned to one of several regularity categories. It discusses various alternative methods which were considered, and explains which were chosen and why. The topics covered in detail are the choice of method, the types of hypotheses which can be made about the hidden topology, and the special case processing used for particular categories of object.
P. A. C. Varley and R. R. Martin, Constructing Boundary Representation Solid Models from a Two-Dimensional Sketch - Geometric Finishing, Proc. First UK-Korea Workshop on Geometric Modeling and Computer Graphics, 145-158, Kyung Moon Publishers, 2000. ISBN 89 7282 445 3
Abstract:
This paper discusses research results useful for producing a system which converts a two-dimensional computer sketch of a single homogeneous polyhedral object into a boundary representation solid model. An overview of our approach to such a system and its main algorithms is presented elsewhere.
This paper gives more detail of some of our methods for producing a finished, geometrically-correct model assuming that previous stages have produced a consistent topology with approximate geometry. It discusses various alternatives which were considered, and explains which were chosen and why. The topics covered in detail are the types of constraint which are generated, optimisation of face normals to meet these constraints, and the special case processing used for particular categories of object.
P. A. C. Varley, H. Suzuki, J. Mitani and R. R. Martin, Interpretation of Single Sketch Input for Mesh and Solid Models, International Journal of Shape Modeling 6 (2), 207-240, 2000.
Abstract:
This paper describes developments in sketch input, with particular reference to two sketching applications: building triangulated mesh models for use in computer graphics, and producing boundary representation models of solid objects for use within a CAD system. Both are driven by the same stroke capture mechanism.
The mesh modelling system interprets a sketch by reference to a topological template. Hidden parts are generated using the template and assumptions of symmetry and axis-alignment. This tool is more useful for capturing curved shapes which conform to a template topology.
The B-rep modelling system makes hypotheses about hidden topology and object geometry based on an estimation of the frontal geometry. The completed topology is chosen by a depth-first search through the tree of hypotheses, and the geometry is finalised using geometric constraint reasoning. This tool is limited to polyhedral shapes without holes, but can cope with a wider range of topologies.
P. A. C. Varley and R. R. Martin, The Junction Catalogue for Labelling Line Drawings of Polyhedra with Tetrahedral Vertices, International Journal of Shape Modeling 7 (1) 23-44, 2001.
Abstract:
The Clowes-Huffman catalogue for labelling line drawings of trihedral polyhedra is a well-established tool in computer vision.
We currently use it in processing sketch input of solid models of engineering components. However, many such components also contain tetrahedral vertices.
Thus, this paper presents a similar catalogue for tetrahedral polyhedra.
P. A. C. Varley and R. R. Martin, Estimating Depth from Line Drawings, Proc. 7th ACM Symposium on Solid Modeling and Applications, SM02, Eds K. Lee, N. Patrikalakis, 180-191, ACM Press, 2002.
Abstract:
Our goal is unassisted machine interpretation of a single line drawing (with hidden lines removed) as a solid object, to create B-rep models of engineering objects from freehand sketches. As partof this process, we seek to deduce a frontal geometry of the object, a 3D geometric realisation of that part of the object visible in the drawing.
Inflation takes a drawing in which all lines have been labelled as convex, concave or occluding, and creates the frontal geometry by adding a z-coordinate to the x- and y-coordinates of each junction in the drawing. This depth information is deduced by attempting to satisfy one or more compliance functions, interpretations of drawing features which can be expressed as equations in junction z-coordinates. This paper examines several compliance functions, and assessing their use in interpretation of engineering objects. It also gives the first rigorous presentation of a new compliance function based on adjacent pairs of junction labels, and removes the previous restriction to trihedral vertices.
This paper also presents the first comparative analysis of application of combinations of compliance functions to a set of test drawings. As a result, we recommend using a combination of edge parallelism with either corner orthogonality or junction label pairs, with the latter being more reliable in general. Use of the face planarity compliance function in combination with these is often beneficial and sometimes necessary.
Peter Ashley Clifford Varley, Automatic Creation of Boundary-Representation Models from Single Line Drawings, PhD Thesis, Department of Computer Science, Cardiff University, 2003.
Abstract:
This thesis presents methods for the automatic creation of boundary-representation models of polyhedral objects from single line drawings depicting the objects. This topic is important in that automated interpretation of freehand sketches would remove a bottleneck in current engineering design methods. The thesis does not consider conversion of freehand sketches to line drawings or methods which require manual intervention or multiple drawings.
The thesis contains a number of novel contributions to the art of machine interpretation of line drawings. Line labelling has been extended by cataloguing the possible tetrahedral junctions and by development of heuristics aimed at selecting a preferred labelling from many possible. The "bundling" method of grouping probably-parallel lines, and the use of feature detection to detect and classify hole loops, are both believed to be original. The junction-line-pair formalisation which translates the problem of depth estimation into a system of linear equations is new. Treating topological reconstruction as a tree-search is not only a new approach but tackles a problem which has not been fully investigated in previous work.
Green Party Election leaflets for the 2003 National Assembly Election: one and two.
P. A. C. Varley, R. R. Martin, Deterministic and Probabilistic Approaches to Labelling Line Drawings of Engineering Objects, International Journal of Shape Modeling 9 (1), 79-99, 2003.
Abstract:
Labelling line drawings is a useful technique in several applications, including that of automated interpretation of line drawings as polyhedral solid objects. Algorithms exist which can in practice label line drawings of trihedral polyhedra correctly in low-order polynomial time. However, the restriction to trihedral polyhedra is too limiting for practical applications.
We are primarily interested in interpreting line drawings of engineering objects, and many of these objects contain non-trihedral (usually tetrahedral) vertices. We therefore investigate two alternative algorithms for labelling drawings of such objects, one deterministic and the other probabilistic. We find that our deterministic solution achieves better results in terms of correctness but can be unacceptably slow, and that our probabilistic solution, while acceptably quick, is less successful in terms of correctness.
Abstract:
In engineering design, much time and effort could be saved if a computer could interpret an engineer's initial concept drawings.
This paper describes a prototype system for interpreting line drawings as solid polyhedral objects. It concentrates on four stages of processing: line labelling, identification of parallel lines, inflation to 2½D, and determination of hidden topology.
Although the system is often successful, particularly with simple drawings, there are also cases where the correct interpretation is obvious to a human but cannot be determined using existing algorithms. The paper gives examples both of the successes of the approach and of typical cases where it cannot replicate human skill.
P. Varley, H. Suzuki and R. R. Martin, Interpreting Line Drawing of Objects with K-Vertices, Proc. Geometric Modeling and Processing 2004, Eds. S.-M. Hu, H. Pottmann, 249-358, 2004. ISBN 0769520782.
Abstract:
As part of the goal of automatic creation of B-rep models of engineering objects from freehand sketches, we seek to take a single line drawing (with hidden lines removed), and from it deduce an initial 3D geometric realisation of the visible part of the drawn object. Junction and line labels, and provisional depth coordinates, are key parts of this frontal geometry.
Many methods for producing frontal geometry only work correctly for drawings of trihedral objects. However, non-trihedral K-vertices commonly occur in engineering objects. We analyse the performance of a line-labelling method applied to K-vertices, and show why methods ignoring geometric considerations are inadequate.
We give a new approach which produces both junction labels and provisional depth coordinates without any prior knowledge. Our results show that even a naive implementation outperforms previous methods.
P. A. C. Varley, R. R. Martin and H. Suzuki, Using Depth Reasoning to Label Line Drawings of Engineering Objects, 9th ACM Symposium on Solid Modeling and Applications SM'04, Eds. G. Elber, N. Patrikalakis and P. Brunet, 191-202, 2004.
Abstract:
Automatic creation of B-rep models of engineering objects from freehand sketches would be of benefit to designers. As part of this process, we first seek to take a single line drawing (with hidden lines removed), and from it deduce an initial 3D geometric realisation of the visible part of the object as drawn. Junction and line labels, and provisional depth coordinates, are important components of this frontal geometry.
Most existing methods for producing frontal geometry use the technique of line labelling, but such methods which take little or no account of geometry. As a result, the line labels produced can be unreliable.
In an earlier paper, we outlined an approach which first inflates a drawing to produce provisional depth coordinates, and from these makes deductions concerning line labels. We showed that even a naive implementation outperforms previous methods of line labelling when applied to a restricted range of drawings.
In this paper, we show how to make further significant enhancements to this approach. We extend the algorithm to non-isometric-projection drawings, consider improved ways of realising some of the concepts, and also consider how to combine this approach with other labelling techniques to gain the benefits of each.
To test our approach, we use a set of drawings which we consider representative sample of drawings of engineering objects; in many cases, these exemplify difficulties not considered in many previous papers on line labelling. We include a comparison, based on this test set, to show that the enhancements we suggest result in significant benefits.
P. A. C. Varley, R. R. Martin and H. Suzuki, Can Machines Interpret Line Drawings?, in ed. J. F. Hughes and J. A. Jorge, Sketch-Based Interfaces and Modelling, Eurographics Symposium Proceedings, 107-116, 2004.
Abstract:
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 state-of-the-art 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 currently-available algorithms. We give examples both of our successes and of typical cases where human skill cannot be replicated.
The following colour plates, illustrating completed object topology obtained
using my prototype system, were unaccountably omitted from the workshop
proceedings.
P. A. C. Varley, Y. Takahashi, J. Mitani and H. Suzuki, A Two-Stage Approach for Interpreting Line Drawings of Curved Objects, in ed. J. F. Hughes and J. A. Jorge, Sketch-Based Interfaces and Modelling, Eurographics Symposium Proceedings, 117-126, 2004.
Abstract:
We describe a two-stage approach for interpreting line drawings of curved objects. In the first stage, the user enters a natural line drawing of a polyhedral template; this is automatically interpreted as the corresponding polyhedral object. In the second stage, the user enters freehand curves; by relating these to the template, a curved object can be constructed.
Peter Varley, Extended Vertices: A Problem for Line Labelling, Proc. Digital Engineering Workshop: 5th Japan-Korea CAD/CAM Workshop, 106-114, 2005.
An extended version of this paper appears as
Peter Varley,
Problems For Line Labelling: A Test Set of Drawings of Objects with Higher-Valency Vertices,
International Journal of CAD/CAM 5 (1), 2005.
Abstract:
Interpreting a natural line drawing as a solid object requires simplifying assumptions in order to make the problem more tractable. Unfortunately, some of the assumptions made in the past have overly simplified the problem. Restricting the order of vertices, and in particular allowing only trihedral vertices, distorts the problem, since algorithms which are satisfactory for the simplified problem are not satisfactory in the general case.
This paper presents a test set of drawings of objects with higher-order vertices. The intention in creating this test set is that it may be used to determine how effective various algorithms are in dealing with general (i.e. unrestricted) order vertices.
HTML version of extended paper here
Ralph Martin, Peter Varley and Hiromasa Suzuki, Perpendicularity as a Key to Interpreting Line Drawings of Engineering Objects, Proc. Digital Engineering Workshop: 5th Japan-Korea CAD/CAM Workshop, 115-120, 2005.
Abstract:
Many recent approaches to the problem of interpreting line drawings as solid objects treat inflation as a two-stage approach, the first stage being to produce a quick initial estimate of vertex z-coordinates, and the second being to refine these initial estimates to produce a "more beautiful" geometry.
By making assumptions about engineering objects and the ways people see and depict them, it is often possible to reproduce a single object which humans will agree is the correct interpretation of the drawing.
Of these assumptions, those to do with perpendicularity are most important, in part because perpendicularity is the most common regularity in engineering objects, and in part because of the importance of perpendicularity in the human perception process. In this paper, we catalogue various possible instances of perpendicularity in engineering drawings.
P. A. C. Varley, R. R. Martin and H. Suzuki, Frontal Geometry from Sketches of Engineering Objects: Is Line Labelling Necessary?, Computer Aided Design 37 (12), 1285-1307, 2005.
Abstract:
A tool which can quickly interpret line drawings (with hidden lines removed) of engineering objects as boundary representation CAD models would be of significant benefit in the process of engineering design. Inflation of the drawing to produce a frontal geometry, a geometric realisation of that part of the object visible in the drawing, is an important stage of this process.
Previous methods of producing frontal geometries have relied on the technique of line-labelling (labelling edges as convex, concave or occluding). Although restricted subsets of the line-labelling problem have known solutions, reliable methods have not been found for the general line-labelling problem, and traditional methods, when adapted to drawings with non-trihedral junctions, are unacceptably slow.
Many other papers assume that line-labelling is an essential step. Here we show this is not necessarily true, and that comparable results can be obtained by a novel alternative approach. Firstly, we consider what outputs from line-labelling are essential to the production of frontal geometry. Secondly, we investigate by what other means these outputs can be produced.
Our work indicates that the only essential output from line-labelling for frontal geometry is the determination of which T-junctions in a drawing are occluding and which are non-occluding. This information is required for inflation, and also for detection of symmetry and for constructing hidden topology.
Thus, we propose and analyse a new method which, in the absence of line labels, simultaneously inflates a drawing to produce the frontal geometry and attempts to determine whether each T-junction is occluding or not. For drawings of objects with holes or pockets, and for cases where line-labelling is particularly unreliable, our new method can provide a better alternative.
R. R. Martin, H. Suzuki and P. A. C. Varley, Labelling Engineering Line Drawings Using Depth Reasoning, Journal of Computing and Information Science in Engineering 5 (2), 158-167, 2005.
N.B. this is a reworking of the SM04 conference paper listed above, not new work.
P. A. C. Varley, R. R. Martin and H. Suzuki, Progress in Detection of Axis-Aligned Planes to Aid in Interpreting Line Drawings of Engineering Objects, in ed. T. Igarashi and J. A. Jorge, Sketch-Based Interfaces and Modelling, Eurographics Symposium Proceedings, 99-108, 2005.
Abstract:
Freehand sketching is an important part of the conceptual design process, and the increasing number of recent sketching applications shows a developing awareness of this importance. We aim to provide an automated tool to turn engineers' freehand sketches into CAD models. This would allow engineers to spend their time more productively and to be more creative.
One natural component of such a tool would be a process for identifying axially-aligned planes implied by a natural line drawing. We present an algorithm for identifying such planes. We illustrate its utility by presenting two uses: identifying planes of mirror symmetry in objects and constructing the hidden topology of objects.
Peter Varley and Pedro Company, Sketch Input of 3D Models: Current Directions, in Proceedings of VISAPP 2007: 2nd International Conference on Computer Vision Theory and Applications, 8 - 11 March, 2007, Barcelona, Spain, Special Session on 3D Model Acquisition and Representation, 85-91. ISBN 978-972-8865-75-7.
Abstract:
In the last few years, there has been considerable interest in sketch input of 3D solid models. This paper summarises recent developments and discusses the directions these developments are taking. We consider three developments in particular: the move away from line labelling as a technique in recognition of the problem posed by extended vertices; the increasing use of symmetry detection as a tool for reconstruction; and progress towards interpretation of drawings depicting curved objects.
Peter A.C. Varley, Comments on “What the Back of the Object Looks Like: 3D Reconstruction from Line Drawings Without Hidden Lines”, IEEE Transactions on Pattern Analysis and Machine Intelligence, Volume 31 Number 6, 1532-1534, August 2009. ISSN 0162-8828.
Abstract:
I comment on a paper describing a method for deducing the hidden topology of an object portrayed in a 2D natural line drawing. The principal problem with this paper is that it cannot be considered an advance on (or even an equal of) the state of the art, as the approach it describes makes the same limiting assumptions as approaches proposed ten years ago. There are also important omissions in the review of related work.
P. Company, N. Aleixos, F. Naya, P.A.C. Varley, M. Contero and D.G. Fernandez-Pacheco, A New Sketch-Based Computer Aided Engineering Pre-Processor, Proceedings of the Sixth International Conference on Engineering Computational Technology, Athens, Greece. 2-5 September 2008. Civil comp Ltd. Paper-149. 2008. ISBN 978-1-905088-24-9 (Book), 978-1-905088-25-6 (CD-ROM), 978-1-905088-26-3 (Set).
Abstract:
Two competing approaches exist for creating input data for Computer-Aided Engineering applications: stand-alone CAE pre-processors which define both geometric data and attributes, and the combination of CAD applications plus downstream CAE pre-processors. In the CAD-CAE sequence, the former defines the geometric information and the latter adds attributes to the imported CAD geometry. In both cases, data is input through WIMP (window/icon/menu/pointing device) user interfaces, which are appropriate during the detailed design phase, but clearly inappropriate during conceptual design.
This paper describes a sketch-based CAE pre-processor as an alternative to the WIMP paradigm. Our prototype implementation is aimed at structural analysis, particularly of 2D bar structures. More generally, we show that sketch-based pre-processors are not merely a valid option in earlier design process stages, but preferable as they increase ease-of-use of user interaction.
Peter Varley and Pedro Company, Automated Sketching and Engineering Culture, in ed. B. Plimmer and T. Hammond, Proc. VL/HCC Workshop on Sketch tools for Diagramming, Herrsching am Ammersee, 15 Sep 2008, 83-92.
Abstract:
In this paper we argue that sketching is an essential part of engineering culture. If current CAD tools cannot support sketching, it is the tools, not the culture, which must change.
We then consider how close we are to having Computer-Aided Sketching tools which meet the requirements of traditional engineering culture. This discussion considers three categories of sketch: thinking sketches, used to focus and guide non-verbal thinking; talking sketches, employed to support discussion of the design with colleagues; and prescriptive sketches, which give instructions to the draftsman in charge of making the finished drawing.
P.A.C. Varley, M. Chover and A. Puig-Centelles, Sketching Islands for a Game Environment, 5th European Conference on Visual Media Production (CVMP 2008).
Abstract:
We present a simple interface for sketching heightmaps of islands. This interface is close to the ideal of a modeless single-tool interface, with all of its major operations being controlled by a single device (pen or single-button mouse). As such is easy to use even for novice users and requires no technical knowledge.
Peter A.C. Varley, Comments on “Plane-Based Optimization for 3D Object Reconstruction from Single Line Drawings”, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol 31 Number 9, 1723-1725, September 2009, ISSN 0162-8828.
Abstract:
I comment on a paper describing a method for inflating a 2D wireframe topological representation of an object to 3D. There are several problems with this paper and the method it describes. An oversimplified problem statement and concentration on mathematical ingenuity rather than comprehension lead the authors to develop a method which is not well-suited to the problem. Failure to take proper account of previous work leads them to compare their method, not with the true state of the art, but with older, less successful approaches. Finally, they omit entirely any mention of, let alone a proposed solution to, the most intractable problem in the area, that of finding resolution sequences.
Anna Puig-Centelles, Peter A.C. Varley, Oscar Ripolles and Miguel Chover, Automatic Terrain Generation with a Sketching Interface, 17th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision (WSCG'09), 2009.
Abstract:
Virtual environments should offer the user a deep interactive experience with both larger worlds to explore and a higher degree of perceived realism. The main goal of our work is to provide the final user with an easy-to-use accurate terrain generation solution, which allows non-professional users to design their own desired terrain. More precisely, in this paper we consider the creation of islands to be used in computer games. In this work we introduce a simple terrain algorithm and we also consider its integration into a sketching application. The application will offer both a 2D and a 3D representation of the terrain, in order to simplify the interface and provide the user with more interactive feedback about the island that has been designed. Our framework offers real-time algorithms for both creating and modifying terrain features, thus improving the final results with more realism and greater customization by the user.
P. Company and P.A.C. Varley, Operating Modes in Actual versus Virtual Paper-and-pencil Design Scenarios, Intelligent User Interfaces (IUI) Workshop on Sketch Recognition, Sanibel Island, Florida, 8th February, 2009..
Abstract:
Conceptual design remains "unplugged" from other computer-aided design tasks. Engineers and designers continue to favor pencil and paper over computerized sketching tools. It has been suggested that one reason for this is the bewilderingly large range of options available to users of CAD tools. The simplicity of pencil and paper, it was argued, is a virtue, not a drawback.
In this paper, we show that, in the hands of a skilled user, a pencil is a complex tool in itself, capable of several different modes of operation. We illustrate this versatility with examples from the field of mechanical engineering. To be competitive, computer-aided sketching tools must support the various operating modes which pencil and paper allows and skilled design engineers habitually use. We discuss to what extent this is already the case, and what further steps can be made towards this goal.
Peter A.C. Varley, The Use of Neighbourhood Matching in Constructing Hidden Object Topology, Proc. 2009 International Conference of Computer Science and Engineering ICCSE'09, 185-190, London 2009.
Abstract:
My interest is automatic interpretation of natural line drawings of
engineering objects. Such drawings only show that part of an object visible
from a particular viewpoint, and the major challenge in interpreting them is
deducing the remaining, unseen part of the topology. Since engineers routinely
use sketched drawings as a means of communicating structure, using well-
established (if unstated) conventions to deduce the invisible topology, it
should be possible to identify these conventions and use them to interpret
such drawings automatically.
One practical approach to constructing the hidden topology is to treat the
construction process as a search through the space of possible complete
topologies. When this approach is used, the most frequent problem is that of
mismatched vertex neighbourhoods: the side of an edge which is convex at one
end is concave at the other.
This paper describes a simple method for overcoming the problem of mismatched
neighbourhoods, and analyses the results which are obtained when this method
is incorporated in the construction process.
Insights gained from this work may also be applicable to other fields, most
obviously perception psychology and the "healing" of CAD models.
Pedro Company, Manuel Contero, Peter Varley, Nuria Aleixos and Ferran Naya, Computer-Aided Sketching as a Tool to Promote Innovation in the New Product Development Process, to appear in Computers in Industry, 2009.
Abstract:
Sketching is an established part of engineering culture. Sketches assist product designers during the creative stages of design and help them to develop inventions. Paper-and-pencil sketching is highly useful but lacks functionalities, mainly because it is disconnected from the rest of the (computer-aided) design process. However, CAS tools are not yet as usable as paper-and-pencil, although they provide full integration with the subsequent phases of the design processes (CAD, CAE, CAM, etc.) and other interesting functionalities. We desire computer-aided sketching (CAS) tools which furnish users with the sketching environment they require to make full use of their conceptual design and innovation talents, while providing full integration with the subsequent phases of the design processes (CAD, CAE, CAM, etc.).
In this paper we discuss the importance of sketching in conceptual design, we review the current situation of engineering sketching, and we then analyze the main characteristics which a successful and fully integrated CAS tool should include. We consider CAS, not as a single problem, but as at least three: thinking, prescriptive and talking sketches require different approaches to functionality. Finally, we present the current state of the art in CAS tools by describing the main features and outstanding problems of our own applications.
P. Company, P.A.C. Varley, A. Piquer, M. Vergara and J. Sánchez-Rubio, Benchmarks for Computer-based Segmentation of Sketches, Proc. Eighth IAPR International Workshop on Graphics Recognition GREC 2009.
Abstract:
In this paper, we study the segmentation of sketched engineering drawings into a set of straight and curved segments. Our immediate objective is to produce a benchmarking method for segmentation algorithms. The criterion is that when evaluating a segmentation algorithm, we wish to minimise the differences between what the algorithm detects and what human beings perceive.
We have created a set of sketched drawings and have asked people to segment them. By analysis of the produced segmentations, we have obtained the number and locations of the segmentation points which people perceive. Besides, some evidences collected during our experiments support useful hypothesis, like that not all kinds of segmentation points are equally difficult to perceive.
The resulting methodology can be repeated with other drawings to obtain a set of sketches and segmentation data which could be used as a benchmark for segmentation algorithms, to evaluate their capability to emulate human perception of sketches.