Graph algorithms and NP-completeness
Graph algorithms and NP-completeness
Machine interpretation of line drawings
Machine interpretation of line drawings
The complexity of recognizing polyhedral scenes
Journal of Computer and System Sciences - 26th IEEE Conference on Foundations of Computer Science, October 21-23, 1985
Recovering Three-Dimensional Shape from a Single Image of Curved Objects
IEEE Transactions on Pattern Analysis and Machine Intelligence
Three-dimensional computer vision: a geometric viewpoint
Three-dimensional computer vision: a geometric viewpoint
On the complexity of labeling perspective projections of polyhedral scenes
Artificial Intelligence
Fundamental properties of neighbourhood substitution in constraint satisfaction problems
Artificial Intelligence
Recovering the shape of polyhedra using line-drawing analysis and complex reflectance models
Computer Vision and Image Understanding - Special issue on physics-based modeling and reasoning in computer vision
Linear-time algorithms for testing the realisability of line drawings of curved objects
Artificial Intelligence
Linear constraints for the interpretation of line drawings of curved objects
Artificial Intelligence
Reduction operations in fuzzy or valued constraint satisfaction
Fuzzy Sets and Systems - Optimisation and decision
Identifying Faces in a 2D Line Drawing Representing a Manifold Object
IEEE Transactions on Pattern Analysis and Machine Intelligence
Evolutionary Search for Faces from Line Drawings
IEEE Transactions on Pattern Analysis and Machine Intelligence
International Journal of Computer Vision
Constraints Between Distant Lines in the Labelling of Line Drawings of Polyhedral Scenes
International Journal of Computer Vision
Exploiting artistic cues to obtain line labels for free-hand sketches
Proceedings of the International Symposium on Sketch-Based Interfaces and Modeling
Genetic algorithm for line labeling of diagrams having drawing cues
Diagrams'12 Proceedings of the 7th international conference on Diagrammatic Representation and Inference
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In line drawings derived from real images, lines may be missing due to contrast failure and objects with curved surfaces may cast shadows from multiple light sources.This paper shows that it is the presence of shadows, rather than contrast failure, that renders the line drawing labelling problem NP-complete. However, shadows are a valuable visual cue, since their presence is formally shown to reduce the average ambiguity of drawings. This is especially true when constraints concerning shadow formation are employed to differentiate shadow and non-shadow lines.The extended junction constraint, concerning straight lines colinear with junctions, compensates the loss of information caused by contrast failure. In fact, we observe the contrast failure paradox: a drawing is sometimes less ambiguous when lines are partly missing due to contrast failure.It is known that the coplanarity of sets of object vertices can be deduced from the presence of straight lines in the drawing. This paper shows that these coplanarity constraints are robust to the presence of contrast failure.