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2 Bulletin of the Polish Academy of Sciences. Technical Sciences

2 1999

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Structural Method in Perceptual Organization of 2D-curve Detection, Representation and Analysis

Jakubowski R., Stąpor K.

Bulletin of the Polish Academy of Sciences. Technical Sciences

1999

Vol. 47, nr 3

309-324

The presented method for 2D-curve detection, representation and analysis is based on the structural model of a shape being developed since the eighties and incorporates perceptual organization for curve segmentation, grouping, identification of distinct low-level perceptual entities known as shape primitives, as well as for grouping shape primitives into contour structures to form successive levels of a hierarchy of shape features. The proposed method consists of the following steps: preprocessing and contour segmentation, detection of critical points in a contour, vectorization (grouping critical points into shape primitives), grouping shape primitives into 2D-contour by joint operation which results in characterological description of a contour, analysis of a 2D-contour using transducer to extract contour features, decomposition of a 2D-contour into quasi-convex figures, generation of context-free grammar which uniquely designates a given 2D-contour.

A Structural Approach to Representation of 3D-objects

Jakubowski R., Stąpor K.

Bulletin of the Polish Academy of Sciences. Technical Sciences

1999

Vol. 47, nr 2

175-189

In this paper a structural method for 3D object modelling and representation is presented. The process of construction of 3D objects is realized by modelling 2D-patterns and extruding them by means of the defind operations: traditional, rotational and generalized extrusion (sweeping) operations. Modelling of 2D-patterns is performed by grouping primitives into 2D features. All the presented extrusion operations are defind on the basis of the shape feature languages (1), (2), (3), (10). Each extrusion operation creates a volume substructed from or added to a solid in order to obtain a 3D feature. Composition of any of such extrusion operations allows grouping of 3D features into 3D-objects with complex, classifiable structures. Parallel to the modelling process the hierarchical graph representation of an object is created which could then be used for feature recognition (6), (7), (9) and object analysis. Using the presented method one can model the machinning of a wide class of prismatic components. The presented method for 3D object representation is then compared with other similar approaches for representation of a 3D object (12), (13).