• Korean Journal of Computational Design and Engineering
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• v.11 no.3
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• pp.205-210
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• 2006

Curve tessellation, which generates a sequence of points from a curve, is very important for curves rendering on a computer screen and for NC machining. For the most case the sequence of discrete points is used rather than a continuous curve. This paper deals with a method of tessellation by calculating the maximal deviation of a curve. The maximal deviation condition is introduced to find the point with the maximal chordal deviation on a curve segment. In the previous research a curve tessellation was tried by the subdivision method, that is, a curve is subdivided until the maximal chordal deviation is less than the given tolerance. On the other hand, a curve tessellation by sequential method is tried in this paper, that is, points are generated successively by using the local property of a curve. The sequential method generates relatively much less points than the subdivision method. Besides, the sequential method can generate a sequence of points from a spatial curve by approximation to a planar curve. The proposed method can be applied for high-accuracy curve tessellation and NC tool-path generation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.349-360
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• 2008

In this paper, the modeling procedure of random field with an elasto-plastic finite element algorithm and probability of failure on closely-spaced tunnel were investigated. Local average subdivision (LAS) method which can generate discrete random variables fast and accurately as well as change the resolution in certain region was used. And correlated value allocating and weighted average method were suggested to implement geometrical characteristics of tunnel. After the probability of failure on the test problem was thoroughly investigated using random finite element method, the results were compared with the deterministic strength reduction factor method and single random variable method. Of particular importance in this work, is the conclusion that the probability of failure determined by simplified probabilistic analysis, in which spatial variability is ignored by assuming perfect correlation, can be estimated from the safety factor determined by strength reduction factor method. Also, single random variable method can lead to unconservative estimates of the probability of failure.

• Journal of Korea Game Society
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• v.11 no.1
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• pp.101-109
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• 2011

The performance of server becomes important issues in online game with the online game market expansion. This paper proposes a method of improving performance to decrease synchronized packets for each entity's informations in game. Our method provides adapted solution of reconstructing spatial subdivision to reduce a load of movement between boundary regions using prediction of entity's movement range and disabled regions where entity can not move to. It is shown through the experiments that proposed method outperforms existing method in terms of processing quantity of packets.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1729-1736
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• 2004

This paper proposes an efficient collision detection method in the dynamic spatial subdivisions for the MMORPG engine which requires realtime interactions. An octree is a suitable structure for static scenes or terrain processing. An octree spatial subdivision enhances rendering speed of scenes. Current spatial subdivisions tend to be highly optimized for efficient traversal, but are difficult to update quickly for a changing geometry. When an object moves to the outside extent for the spatial subdivisions, the acceleration structure would normally have to be rebuilt. The OSP based on a tree is used to divide dynamically wide outside which is the subject of 3D MMORPG. TBV does not reconstruct all tree nodes of OSP and has reduced rebuilding times by TBV information of a target node. A collision detection is restricted to those objects contained in the visibility range of sight by using the information established in TBV. We applied the HBV and ray tracing for an efficient collision detection.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.4
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• pp.101-110
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• 1996

Color image quantization is a process of selecting a set of colors to display an image with some representative colors without noticeable perceived difference. It is very important in many applications to display a true color image in a low cost color monitor or printer. the basic problem is how to display 224 colors with 256 or less colors, called color palette. In this paper, we propose an algorithm to design the 256 or less size color palette by using spatial maskin geffect of HVS and subjective distortion measure weighted by color palette by using spatial masking effect of HVS and subjective distortion measure weighted by color activity in 4*4 local region in any color image. The proposed algorithm consists of octal prequantization and subdivision quantization processing step using the distortion measure and modified Otsu's between class variance maximization method. The experimental results show that the proposed algorithm has higher visual quality and needs less consuming time than conventional algorithms.

• Fire Science and Engineering
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• v.3 no.2
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• pp.11-19
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• 1989

In this study, the independent variables are the floor plan configulation. The dependent variables are the occupant's egress behavior, especially spatial movement pattern, and life - safety performance of building. Fire events were simulated on single story of office building. Simulation run for allowable secaping thime(180 seconds) arbitrarily selected, and involved 48 occupants. The major findings Pre as follows. 1) Computer simulation model suggested in this study can be used as the Preoccupancy evaluation method of the life-safety performance for architectural design based on prediction of occupants' egress behavior in the levels of validity and sensitivity, 2) Sucess or failure in occupants' escape is determined by decreasing walking speed caused by jamming at exits or over crowded corridor, and increasing route length caused by running about in confusion at each subdivision and corridor. 3) In floor plan configuration which safe areas located at the extreme ends of the corridor, cellular floor planning have to be avoided preventing jamming and running about in confusion at overcrowded corridor.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.157-157
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• 2017

To minimize the damage by wild birds and acquire the benefits such as protection against weeds and maintenance of water content in soil, the mulching black color vinyl after seeding should be carried out. Non-contact and non-destructive methods that can continuously determine the locations are necessary. In this study, a crop position detection method was studied that uses infrared thermal image sensor to determine the cotyledon position under vinyl mulch. The moving system for acquiring image arrays has been developed for continuously detecting crop locations under plastic mulching on the field. A sliding mechanical device was developed to move the sensor, which were arranged in the form of a linear array, perpendicular to the array using a micro-controller integrated with a stepping motor. The experiments were conducted while moving 4.00 cm/s speed of the IR sensor by the rotational speed of the stepping motor based on a digital pulse width modulation signal from the micro-controller. The acquired images were calibrated with the spatial image correlation. The collected data were processed using moving averaging on interpolation to determine the frame where the variance was the smallest in resolution units of 1.02 cm. Non-linear integral interpolation was one of method for analyzing the frequency using the normalization image and then arbitrarily increasing the limited data value of $16{\times}4pixels$ in one frame. It was a method to relatively reduce the size of overlapping pixels by arbitrarily increasing the limited data value. The splitted frames into 0.1 units instead of 1 pixel can propose more than 10 times more accurate and original method than the existing correction method. The non-integral calibration method was conducted by applying the subdivision method to the pixels to find the optimal correction resolution based on the first reversed frequency. In order to find a correct resolution, the expected location of the first crop was indicated on near pixel 4 in the inversion frequency. For the most optimized resolution, the pixel was divided by 0.4 pixel instead of one pixel to find out where the lowest frequency exists.

• Journal of Korea Game Society
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• v.11 no.5
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• pp.23-30
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• 2011

Flocking behaviors are frequently used in games and computer graphics for realistic simulation of massive crowds. Since simulation of massive crowds in real time is a computationally intensive task, there were many researches on efficient algorithm. In this paper, we find experimentally the fact that there are unnecessary computations in the previous efficient flocking algorithm, and propose a noble algorithm that overcomes the weakness of the previous algorithm with a simple heuristic. A number of experiments were conducted to evaluate the performance of the proposed algorithm. The experimental results showed that the proposed algorithm outperformed the previous efficient algorithm by about 21% on average.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.95-104
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• 1989

This paper presents a new shadow testing acceleration scheme for ray tracing called Hybrid Shadow Testing (HST) based on a conditional switching between the conventinal shadow testing method and Crow's shadow volume method, where the shadow polygons as well as the object polygons are registered onto the corresponding cells under the 3-D space subdivision environment. Despite the preprocessing time for the generation and registration of the shadow polygons, the total shadow testing time of the proposed algorithm, HST was approximately 50% of that of the conventional shadow testing method for several examples while the total ray tracing time was typically reduced by 30% from the conventional approach. This due to the selective use of the shadow volume method with a compromise between the maximal utilisation of shadow's spatial coherency and minimising the computational overhead for checking ray intersections with the shadow polygons. A parameter, $N_{th}$ denoting the critical number of shadow polygons between successive reflection points was used as a guideline for switching the shadow testing scheme between the conventional method and shadow volume method. A method for calculating $N_{th}$ from such statistical data as the number of object polygons, average polygon size average peripheral length of the polygons was proposed, resulting in good agreement with the experimental results.

• Journal of architectural history
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• v.11 no.3 s.31
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• pp.21-34
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• 2002

This study is to analyse the transformation process of spatial structure of traditional small city structure in Jeollabuk-Do in the process of modern urbanization between 19th century and the year 2000. The small cities, IM-PI, YONG-AN, YEO-SAN, OK-GOO, GO-SAN, MU-JANG, GUM-MA, GO-BU, which have been local administrative center in CHO-SUN dynasty, have role of local administrative center of subdivision of country-myon, except OK-GOO. The method of this study is to investigate the transformation process of spatial structural elements of with the actual field surveys, the analysis of Gunhyun map made in 1872, land registration maps in 1910s and 2000, and various topological maps. The elements of analysis are the topological site and geographical situation conditions, the urbanized areas, the street systems, the function of streets, the focal points of urban land use, the land use systems, and the location of major facilities such as administration facilities, markets, bus terminals. The analytical point of view and the results are as follows. There is strong relationship between the transformation of internal matrix route system and the growth pattern of urbanized areas, Especially on the contrary to the matrix route with East-West direction which has the role of checking the growth of urbanized area, the South-North direction route acts as the leading line of the growth. The focal points structure of urban land use shows transformation process from the point of central space of administrative district in front of Nae-A, to the access point to administrative district or to the access point to housing and neighborhood commercial area. From the point of functional area structure and major facilities location, line-type commercial area is developed along the line of central axis route and access route to administrative district. Especially direction of the growth of commercial area is strongly connected with the interrelationship between the study area and its neighboring cities. Pattern of commercial district development is varied with the direction of matrix route. That is, commercial district, which shows one side development pattern along the East-West direction route, is developed on both sides of street along the South-North direction route.