The Use of Objects' Faces in Interpreting Line Drawings

IEEE Transactions on Pattern Analysis and Machine Intelligence, 1985

This paper deals with the interpretation and feasibility check of line drawings representing polyhedral scenes. The polyhedra are of general types and there are no restrictions on camera position. The geometric consistency check and the line labeling are carried out through constructions in the image plane. An algorithm for the geometric construction is suggested, and the necessary conditions for these constructions are discussed. The image plane construction can be used for preparing labeled junictioii catalogs for junctions other than trihedral. In addition the paper analyzes the relation between the image plane construction and the gradient space construction suggested by Mackworth [7] for the same purpose. Index Terms-Computer vision, machine intelligence, polyhedral line drawing, projective geometry, scene analysis.

International Journal of Computer Vision, 2006

The machine interpretation of line drawings has applications both in vision and geometric modelling. This paper extends the classic technique of assigning semantic labels to lines subject to junction constraints, by introducing new constraints (often between distant lines). These include generic constraints between lines lying on a path in the drawing as well as preference constraints between the labellings of pairs of junctions lying on parallel lines. Such constraints are essential to avoid an exponential number of legal labellings of drawings of objects with non-trihedral vertices. The strength of these constraints is demonstrated by their ability to identify the unique correct labelling of many drawings of polyhedral objects with tetrahedral vertices. These new constraints also allowed us to deduce a general polyhedral junction constraint for the case when there is no limit on the number of faces which can meet at a junction.

Image and Vision Computing, 1993

Before research on the machine interpretation of line drawings can find practical applications it is essential to study realistic models of real-world objects. This paper extends the work of Malik on curved objects with piecewise C' surfaces. In particular, a new catalogue of junction labellings is given when smooth edges (discontinuities of surface curvature) are permitted on object surfaces.

ACM Transactions on Applied Perception

In this paper, visual perception principles were used to build an artificial perception model aimed at developing an algorithm for detecting junctions in line drawings of polyhedral objects that are vectorized from hand-drawn sketches. The detection is performed in 2D, before any 3D model is available and minimal information about the shape depicted by the sketch is used. The goal of this approach is to not only detect junctions in careful sketches created by skilled engineers and designers, but also detect junctions when skilled people draw casually to quickly convey rough ideas. Current approaches for extracting junctions from digital images are mostly incomplete, as they simply merge endpoints that are near each other, thus ignoring the fact that different vertices may be represented by different (but close) junctions and that the endpoints of lines that depict edges that share a common vertex may not necessarily be close to each other, particularly in quickly sketched drawings. We describe and validate a new algorithm that uses these perceptual findings to merge tips of line segments into 2D junctions that are assumed to depict 3D vertices.

Expert Systems with Applications, 1998

1987

Reviewed by WALTER WHITELEY The author obtained his advanced training in the Engineering Division of the University of Tokyo and is currently an Associate Professor in the Department of Mathematical Engineering and Instrumentation Physics at that university. His primary research interests involve the topics of the book under review and related matroid theory and combinatorial algorithms.

2004

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.

Computer-Aided Design, 2005

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.

Artificial Intelligence, 2000

Drawings of curved objects often contain many linear features: straight lines, colinear or coplanar points, parallel lines and vanishing points. These linear features give rise to linear constraints on the 3D position of scene points. The resulting problem can be solved by standard linear programming techniques. An important characteristic of this approach is that instead of making a strong assumption, such as all surfaces are planar, only a very weak assumption, which disallows coincidences and highly improbable objects, needs to be made to be able to deduce planarity. The linear constraints, combined with junction-labelling constraints, are a powerful means of discriminating between possible and impossible line drawings. They provide an important tool for the machine reconstruction of a 3D scene from a human-entered line drawing.

We describe a two-stage approach for interpreting line drawings of curved objects. In the first stage, the user en- ters a natu-ral line drawing of a polyhedral template; this is automatically interpreted as the corresponding poly- hedral object. In the second stage, the user enters freehand curves; by relating these to the template, a curved ob- ject can be constructed