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Contouring Medial Surface of Thin-Plate Structures Using Local Marching Cubes

[+] Author and Article Information
Tomoyuki Fujimori, Hiromasa Suzuki, Yohei Kobayashi

 The University of Tokyo, Tokyo, Japan

Kiwamu Kase

 The Institute of Physical and Chemical Research, Saitama, Japan

J. Comput. Inf. Sci. Eng 5(2), 111-115 (Feb 22, 2005) (5 pages) doi:10.1115/1.1891823 History: Received September 04, 2004; Revised February 22, 2005

This paper describes a new algorithm for contouring a medial surface from CT (computed tomography) data of a thin-plate structure. Thin-plate structures are common in mechanical structures, such as car body shells. When designing thin-plate structures in CAD (computer-aided design) and CAE (computer-aided engineering) systems, their shapes are usually represented as surface models associated with their thickness values. In this research, we are aiming at extracting medial surface models of thin-plate structures from their CT data for use in CAD and CAE systems. Commonly used isosurfacing methods, such as marching cubes, are not applicable to contour the medial surface. Therefore, we first extract medial cells (cubes comprising eight neighboring voxels) from the CT data using a skeletonization method to apply the marching cubes algorithm for extracting the medial surface. It is not, however, guaranteed that the marching cubes algorithm can contour those medial cells (in short, not “marching cubeable”). In this study, therefore we developed cell operations that correct topological connectivity to guarantee such marching cubeability. We then use this method to assign virtual signs to the voxels to apply the marching cubes algorithm to generate triangular meshes of a medial surface and map the thicknesses of thin-plate structures to the triangle meshes as textures. A prototype system was developed to verify some experimental results.

FIGURES IN THIS ARTICLE
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Copyright © 2005 by American Society of Mechanical Engineers
Topics: Algorithms , Thickness
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Figures

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Figure 1

An overview of our method: CT data (a), thresholding (b), thinning (c), guarantee marching cubes (d), virtual sign assignment (e), and isosurfacing (f)

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Figure 2

Face points are centers of a cell’s faces (a), and a face point has eight D neighbors and six A neighbors (b)

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Figure 3

Left: A two-dimensional example of Prohaska’s skeletonization method applied to cells. Right: An example of face-point skeletonization. Both methods use geodesic distances, however, f-point skeletonization uses center points of the cell’s face to find nearest boundary points.

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Figure 4

Cells represent a thin-plate structure dividing background cells into 1, 2, or 3 areas

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Figure 5

Left shows isoface and isoedge are passed through by isosurfaces. Right shows three isoedges that are perpendicular to each other creates a hole on isosurfaces.

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Figure 6

Left: A photograph of the target aluminum pipe. This pipe has both thin and thick parts. Center and right: Generated medial surfaces using our proposed method.

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Figure 7

These figures show a part-forming process with progressive drawing. Left: A medial surface of an iron plate, which is an initial iron plate to form. Center: The result of the first stamping process, and right: the 2nd work.

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