• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.1
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• pp.68-74
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• 2000

The STL file format is an approximation of 3-D model with triangular facets. STL is a standard input file format of Rapid Prototyping(RP) equipment In computer graphics a circle has been approximated with an inscribed polygon which causes an error between the real and approximated circles. In this study an intersecting polygon has been used to approximate the circle and applied to produce more accurate RP part. The newly proposed method shows it's excellence in part accuracy.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.81-86
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• 1999

The STL file format is an approximation of 3-D model with triangular facets. STL is a standard input file format of Rapid Prototyping(RP) equipment. In computer graphics, a circle has been approximated with an inscribed polygon, which causes an error between the real and approximated circles. In this study, an intersecting polygon has been used to approximate the circle and applied to produce more accurate RP part. The newly proposed method shows it's excellence in part accuracy.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.8
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• pp.1270-1281
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• 1989

This paper presents two new storage schemes of 3-D objects to accelerate the finding of the first intersecting object and the shadow computation steps in ray tracing. The 3-D objects which are potentially intersected with the first reflection (refraction)ray are enrolled within a so called reflection (refraction) frustum' for a polygon object. Only those objects registered in the corres ponding frustum are immediately checked for intersection with the secondary rays emanating from the same polygon. The other is called a shadow pyramid' which contains the candidate objects possibly blocking the path from the relevant light source to any point on the relevant polgon. The shadow testing of a point is performed only against the objects contained in the associated shadow pyramid. Despite the cost needed for registration of objects within frusta or shadow pyramids, the total rendering time of ray tracing using the proposed approaches was reduced by approximately 50% (10% in color rendering time and 70% in shadoe testing time) from the conventional cell 50% (10% in color rendering time and 70% in shadow testing time) from the conventional cell traversal scheme under the 3-D uniform subdivision environment due to the fast finding of candidate objects for intersection and the reduced number of intersection calculations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2009-2018
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• 2001

This paper presents a region offsetting algorithm for tool-path generation. The proposed region offsetting algorithm is developed by expanding the 'PWID offset algorithm [Choi and Park, 1999]'designed to offset a simple polygon. The PWID offset algorithm has three important steps; 1) remove 'local invalid ranges'by invoking a PWID test, 2) construct a raw offset owe and 3) remove 'global invalid ranges'by finding self-intersections of the raw offset cure. To develop a region offsetting algorithm, we modified the PWID offset algorithm by expanding the concept of the 'global invalid range'in the third step. The time complexity of the proposed algorithm is approximately Ο(n), where n is the number of points, and it is free of numerical errors for practical purposes. The proposed algorithm has been implemented and tested with various real regions obtained by intersecting a sculptured surface with a plane.

• Journal of the Korea Computer Industry Society
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• v.2 no.2
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• pp.157-164
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• 2001

This paper studies on the processing of spatial joins. The spatial join operation is divided into filters and refinement steps in general. The processing of spatial joins can be greatly improved by the use of filters that reduce the polygons in order to find the intersecting ones. As a result, three possible sets of answers are identified: the positive one, the negative one and the inconclusive one. To identify all the interesting pairs of polygons with inconclusive answers, it is necessary to have access to the representation of polygons so that an exact geometry test can take place. We introduce a bit-map approximation technique to drastically reduce the computation required by the refinement step during refinement processing. Bit-map representation are used for the description of the internal, the external and the boundary regions of the polygon objects. The proposed scheme increases the chance of trivial acceptance and rejection of data objects, and reduces unnecessary disk accesses in query processing. It has been shown that the reference to the object data file can be cut down by as much as 60%.