Comments on "what the back of the object looks like: 3D reconstruction from line drawings without hidden lines"

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 10 years ago. There are also important omissions in the review of related wor

A method for reconstructing sketched polyhedral shapes with rounds and fillets

In this paper we present a method for detecting rounds and fillets in engineering sketches and drawings, and automatically generating a 3D model of the corresponding object, with rounds and fillets applied. This method is useful both as a component of computer-aided sketching tools and in determining de- sign intent—although rounds and fillets are common in engineering parts, they often conceal design intent, which is more easily determined from the object’s underlying polyhedral skeleton

A fast approach for perceptually-based fitting strokes into elliptical arcs

Fitting elliptical arcs to strokes of an input sketch is discussed. We describe an approach which automatically combines existing algorithms to get a balance of speed and precision. For measuring precision, we introduce fast metrics which are based on perceptual criteria and are tolerant of sketching imperfections. We return a likelihood estimate based on these metrics rather than deterministic yes/no result, in order that the approach can be used in higher-level collaborative-decision recognition flows.1) Ramon y Cajal Scholarship Programme 2) "Pla de Promoció de la Investigació de la Universitat Jaume I", project P1 1B2010-0

Perimeter detection in sketched drawings of polyhedral shapes

Ponència presentada al STAG17: Smart tools and Applications in Graphics, celebrat a Catania (Itàlia) 11-12 setembre 2017This paper describes a new “envelope” approach for detecting object perimeters in line-drawings vectorised from sketches of polyhedral objects. Existing approaches for extracting contours from digital images are unsuitable for Sketch-Based Modelling, as they calculate where the contour is, but not which elements of the line-drawing belong to it. In our approach, the perimeter is described in terms of lines and junctions (including intersections and T-junctions) of the original line drawing

Perceiving ribs in single-view wireframe sketches of polyhedral shapes

As part of a strategy for creating 3D models of engineering objects from sketched input, we attempt to identify design features, geometrical structures within objects with a functional meaning. Our input is a 2D B-Rep derived from a single view sketch of a polyhedral shape. In this paper, we show how to use suitable cues to identify algorithmically two additive engineering design features, angular and linear ribs

Automatic Creation of Boundary-Representation Models from Single Line Drawings

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. Thge thesis contains a number of..

A new algorithm for finding faces in wireframes

The problem of identifying the topology implied by wireframe drawings of polyhedral objects requires the identification of face loops, loops of edges which correspond to a face in the object the drawing portrays. In this paper, we survey the advantages and limitations of known approaches, and present and discuss test results which illustrate the successes and failures of a currently popular approach based on Dijkstra's Algorithm. We conclude that the root cause of many failure cases is that the underlying algorithm assumes that the cost of traversing an edge is fixed. We propose a new polynomial-order algorithm for finding faces in wireframes. This algorithm could be adapted to any graph-theoretical least-cost circuit problem where the cost of traversing an edge is not fixed but context-dependent. © 2010

CSG Feature Trees from Engineering Sketches of Polyhedral Shapes

We investigate the problem of determining design intent from engineering sketches: what did the designer have in mind when sketching a component? Specifically, we consider the unidirectional reverse mapping from form features, as determined from an input sketch, to design features, representing the design intent present in the designer’s mind. We introduce a list of com- mon engineering form features. For each, we list which geometrical cues may be helpful in identifying these features in design sketches, and we list the design features which such form features commonly imply. We show that a reductionist approach which decomposes a diagram into form features can be used to deduce the design intent of the object portrayed in a drawing. We supply experimental results in support of this idea

Computer-aided sketching as a tool to promote innovation in the new product development process

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. © 2009 Elsevier B.V. All rights reserved