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Research Papers

Global Tangent Visibility Analysis for Polyhedral Computer Aided Design Models

[+] Author and Article Information
Zhi Yang

Department of Industrial and Manufacturing Engineering,  The Pennsylvania State University, University Park, PA 16802zxy119@psu.edu

Richard A. Wysk

Department of Industrial and System Engineering,  North Carolina State University, Raleigh, NC 27695

Sanjay Joshi

Department of Industrial and Manufacturing Engineering,  The Pennsylvania State University, University Park, PA 16802

J. Manuf. Sci. Eng 133(3), 031012 (Jun 10, 2011) (9 pages) doi:10.1115/1.4004141 History: Received October 06, 2010; Revised April 19, 2011; Published June 10, 2011; Online June 10, 2011

Visibility analysis is broadly used in milling and casting process planning and in coordinate measuring machine applications. However, standard visibility analysis (which involves determining visibility from a given viewpoint), cannot be applied directly to in-line cutting systems such as wire electrical discharge machines or hot wire foam cutters. The motivation of this paper is to accurately calculate the tangent visibility for objects represented by polygonal surfaces. In this paper we define a new type of visibility - tangent visibility. We develop an algorithm to calculate the global tangent visibility for in-line cutting systems, and several models are tested to verify its accuracy. Several polyhedral models are tested to verify the correctness of the tangent visibility algorithm; and the complexity of the algorithm is also discussed.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Difference between common visibility and tangent visibility

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Figure 2

Comparison of common visibility and tangent visibility

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Figure 3

A point with its tangent surface

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Figure 4

Convex edge and concave edge examples

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Figure 5

Examples illustrating definition of tangent visibility

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Figure 6

Three major steps for calculating tangent visibility

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Figure 7

Illustration of an intersection graph

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Figure 8

Algorithm for computing the intersection graph

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Figure 9

Flowchart illustrating how to compute tangent visibility for a polygon

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Figure 10

Algorithm for computing the tangent visibility

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Figure 11

Algorithm for the Edge_Intersect_Test subfunction

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Figure 12

Algorithm for the Form Region subfunction

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Figure 13

Algorithm for the Form_Rects subfunction

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Figure 14

Algorithm for the Form_Triangle subfunction

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Figure 15

Algorithm for the Form_Cones subfunction

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Figure 16

Software structure of tangent visibility system

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Figure 17

Example, Part I

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Figure 19

Example, Part III

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Figure 20

Tangent invisible triangles on human femur model (tangentially invisible facets are colored)

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