Solid reconstruction from orthographic views using 2-stage extrusion

In this paper, a method called 2-stage extrusion is proposed to reconstruct a solid by modifying the incremental extrusion [Shum SSP. Solid reconstruc tion from orthographic opaque views using incremental extrusion. Computers & Graphics 1997;21(6):787-800; Shum SSP et al. A low-cost wireframe-to-soli d implementation for reverse engineering. AUTOFACT'97 Conference, 3-6 Novem ber 1997, MS98(159), 1-7] for translucent object domain. The algorithm has two extrusion stages. In each stage, geometric entities from only three ort hogonal views (viz. top, front and right) are used. The entities involve bo th solid and dashed lines in each view. In the first stage, an exterior con tour region in each view is swept along its normal direction according to t he corresponding object dimension. As a result, three extrusion-solids are produced. Intersection of the three extrusion-solids forms a basic-solid. N ext, all interior entities of each view are treated by a filtering process. If all interior entities are discarded in the filtering, the second stage will be skipped and the basic-solid becomes a solution-solid. On the other hand, if any interior entity remains after filtering, they are processed in the second stage to generate an excess-solid. In this case, the basic-soli d subtracts the excess-solid to form the final three-dimensional solution-s olid. (C) 2000 Elsevier Science Ltd. All rights reserved.