• ETRI Journal
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• v.40 no.3
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• pp.366-375
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• 2018

Recently, techniques involving head-mounted displays (HMDs) have attracted much attention from academia and industry owing to the increased demand for virtual reality and augmented reality applications. Because HMDs are positioned near to users' eyes, it is important to solve the accommodation-vergence conflict problem to prevent dizziness. Therefore, holography is considered ideal for implementing HMDs. However, within the Nyquist region, the accommodation effect is limited by the space-bandwidth-product of the signal, which is determined by the sampling number of spatial light modulators. In addition, information about the angular spectrum is duplicated over the Fourier domain, and it is necessary to filter out the redundancy. The size of the exit-pupil of the HMD is limited by the Nyquist sampling theory. We newly propose a holographic HMD with an expanded exit-pupil over the Nyquist region by using the time-multiplexing method, and the accommodation effect is enhanced. We realize time-multiplexing by synchronizing a high-speed digital micromirror device and a liquid-crystal shutter array. We also demonstrate the accommodation effect experimentally.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.5
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• pp.947-956
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• 2021

As an interest in metaverse increases, there are many studies to apply virtual reality to indirect experiences. Virtual reality is increasingly being used not only for entertainment such as games but also for educational content. A key technology of indirect experience is modeling an object to provide a realistic experience to the user. Natural environments such as tidal flats change with time, and many living things also live there. In this paper, we propose a method for creating experiential content that accurately models the ecological environment of tidal flats. The proposed method explains how to naturally model the temporal change of tidal flats. We also explain how to model a crab, a creature that inhabits the tidal flat, in the forms of an NPC using the behavior tree. Implementation results show that the proposed method uses simple algorithms but expresses the shapes of tidal flats well.

• Journal of People, Plants, and Environment
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• v.22 no.3
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• pp.309-319
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• 2019

This study was conducted to investigate the effects of watching a virtual reality (VR) forest video on stress reduction in adults. Experiments were performed in an artificial climate chamber where temperature, humidity and illumination were controlled. To cause stress in subjects, the subjects were asked to multiply two digit numbers by one digit numbers for two minutes. The subjects then watched a VR forest video for five minutes. During the experiment, the heart rate variability (HRV) and heart rate (HR) of subjects were continuously measured for evaluating their physiological state. After measuring the baseline and watching a VR forest video, their psychological state was evaluated using the profile of mood state (POMS), semantic differential (SD) method, and positive affect and negative affect schedule (PANAS). The results of physiological evaluation after watching a VR forest video showed a decrease in the stress index and HR, an increase in the activity of the parasympathetic nervous system, and the standard deviation of normal to normal RR intervals (SDNN). The results of psychological assessment confirmed that watching a VR forest video induced "comfort", "natural", and "soothed" feelings in subjects. In addition, watching a VR forest video decreased "tension-anxiety (T-A)", "depression-dejection (D)", "anger-hostility (A-H)", "fatigue (F)", "total mood disturbance (TMD)", and increased "vigor (V)" compared to the base line, and decreased "negative affect" and increased "positive affect." These results indicate that watching a VR forest video decreases adults' stress index, stabilizes physiological state, and has a positive impact on psychological state. The findings of this study can serve as a basis for providing forest welfare services to people in the blind spots of forest welfare, and can lay a foundation for the adoption of VR, one of the technologies of the fourth industrial revolution in forestry.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06a
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• pp.17-21
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• 1998

시점 합성(View synthesis)이란 일반적으로 주어진 기준 영상들(reference viewpoint images 혹은 key frames)으로부터 임의의 시점에서 바라본 영상을 예측하여 합성하는 것을 의미한다. 이러한 시점 합성은 영상 기반 렌더링(Image-based rendering)기법의 일종으로 컴퓨터 그래픽스 분야에서 실시간 렌더링이나 가상 현실(Virtual reality) 구현을 위한 매우 강력한 접근 방식이다. 시점 합성은 물체를 표현하기 위한 3차원 모델링이 필요가 없으며, 렌더링 시간이 물체의 복잡도와는 무관한 장점이 있다. 이러한 시점 합성 기법으로 물체의 3차원 표현과 효과적인 데이터베이스 구축에 응용이 가능하다. 본 논문에서는 물체의 3차원 데이터베이스 구축을 위해 영상 기반 렌더링 기법에 근거한 간단하고, 효과적인 시점 합성 방법을 제안한다.

• Journal of the Korea Computer Graphics Society
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• v.13 no.3
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• pp.19-24
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• 2007

In this paper, we describe a method of defining an object's real length in order to compare objects' lengths precisely using all real length units in the real world. The browser in our study represents an object's length by referencing to the physical length property defined at modeling when it displays the object. Since objects' lengths are appropriately scaled according to these units, objects can be precisely and visually compared in sire using real world length units. The concept of defining the real length unit is extended to the X3D specification. The units are ranged from $10^{-24}(yotta)\;to\;10^{24}(yocto)$. In addition, we explain the method for processing LOD (Levels Of Detail) and for applying the property of LOLD (Levels of Length Detail) when objects with different LOLD are read into the browser.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.3-15
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• 2008

This study aims to simulate the 3 dimensional (3D) model of Keum-man connection canal using geographic information system (GIS) as well as considering design in viewpoint of engineering. The canal connects from Keumkang to Mangyungkang in order to supply fresh water into Saemankeum lake. This study used 3 dimensional spatial planning model (3DSPLAM) process to generate the 3D model, which has not only several planning layers in actual process, but also their corresponding layers in modeling process to simulate 3D space of rural villages. The discharge of the canal is $20m^3/s$ on slope of 1/28,400 in the canal length of 14.2km, which consists of pipe line and open channel. This study surveyed the route of the canal and its surrounding environment for facilities to make images in the 3D graphic model. Besides, the present study developed data set in GIS for geogrphical surface modeling as well as parameters in hydraulic analysis for water surface profile on the canal using HEC-RAS model. From the data set constructed, this study performed analysis of water surface profile with HEC-RAS, generation of digital elevation model (DEM) and 3D objects, design of the canal section and route on DEM in AutoCAD, and 3D canal model and its surrounding 3D space in 3DMAX with virtual reality. The study result showed that the process making 3D canal model tried in this study is very useful to generate computer graphic model with the designed canal on the surface of DEM. The generated 3D canal can be used to assist decision support for the canal policy.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1074-1080
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• 2006

Motion capture systems are gaining popularity in entertainment, medicine, sports, education, and industry, with animation and gaming applications for entertainment taking the lead. A wide variety of systems are available for motion capture, but most of them are complicated and expensive. In the general class of optical motion capture, two or more optical sensors are needed to measure the 3D positions of the markers attached to the body. Recently, a 3D motion capture system using two Position Sensitive Detector (PSD) optical sensors was introduced to capture high-speed motion of an active infrared LED marker. The PSD-based system, however, is limited by a geometric calibration procedure for two PSD sensor modules that is too difficult for common customers. In this research, we have introduced a new system that used a single PSD sensor unit to obtain 3D positions of active IR LED-based markers. This new system is easy to calibrate and inexpensive.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.169-173
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• 2000

현재 컨테이너 터미널에서 사용되고 있는 하역 장비들은 크게 하역작업을 수행하는 크레인과 컨테이너를 운반하는 트레일러, 컨테이너의 하역상태를 파악하는 모니터링 시스템으로 구분할 수 있다. 각각의 장비들은 수동으로 동작되며, 모니터링 시스템에서는 컨테이너의 위치 및 수량 등을 파악한다. 이런 시스템 하에서는 모든 항만 하역 장비들을 사람이 일일이 수동으로 조작함으로써 많은 인력이 필요하다. 또한, 각 하역장비들의 상태를 평면적인 2차원 화면으로만 보여주므로써 모니터링 시스템에 대한 현실감이 떨어진다. 이와 같은 단점을 보완하기 위해 컨테이너를 자동으로 운반하는 AGV를 도입하고 트랜스퍼 크래인과 컨테이너 크레인의 일부분을 자동화하여 작업능률을 향상시키고, 여기에 3차원으로 표현된 VR 시스템을 도입하여 각 하역장비들에 대한 세세한 동작까지를 모니터링함으로써 사용자가 현장에 있는 것과 유사한 느낌을 가질 수 있도록 하였다. 본 논문에서는 이러한 3차원 VR시스템과 모형으로 만들어진 AGV와 컨테이너 크레인, 트랜스퍼 크레인간의 유기적인 데이터 송,수신 및 안정적인 통신을 위해 데이터 포맷에 대한 연구를 하였다. 이런 데이터 포맷의 결정은 손실 없는 통신을 보장하며 나아가 정확한 모니터링을 보장할 것이다.

• Journal of the Korea Society of Computer and Information
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• v.12 no.2 s.46
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• pp.21-28
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• 2007

The facial modeling and animation technology had been studied in computer graphics field. The facial modeling technology is utilized much in virtual reality research purpose of MPEG-4 and so on and movie, advertisement, industry field of game and so on. Therefore, the development of 3D facial model that can do interaction with human is essential to little more realistic interface. We developed realistic and convenient 3D facial modeling system that using a optional facial image only. This system allows easily fitting to optional facial image by using the Korean standard facial model (generic model). So it generates intuitively 3D facial model as controling control points elastically after fitting control points on the generic model wire to the optional facial image. We can confirm and modify the 3D facial model by movement, magnify, reduce and turning. We experimented with 30 facial images of $630{\times}630$ sizes to verify usefulness of system that developed.

• Progress in Medical Physics
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• v.14 no.1
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• pp.34-42
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• 2003

In medical imaging, three-dimensional (3D) display using Virtual Reality Modeling Language (VRML) as a portable file format can give intuitive information more efficiently on the World Wide Web (WWW). The web-based 3D visualization of functional images combined with anatomical images has not studied much in systematic ways. The goal of this study was to achieve a simultaneous observation of 3D anatomic and functional models with planar images on the WWW, providing their locational information in 3D space with a measuring implement using VRML. MRI and ictal-interictal SPECT images were obtained from one epileptic patient. Subtraction ictal SPECT co-registered to MRI (SISCOM) was performed to improve identification of a seizure focus. SISCOM image volumes were held by thresholds above one standard deviation (1-SD) and two standard deviations (2-SD). SISCOM foci and boundaries of gray matter, white matter, and cerebrospinal fluid (CSF) in the MRI volume were segmented and rendered to VRML polygonal surfaces by marching cube algorithm. Line profiles of x and y-axis that represent real lengths on an image were acquired and their maximum lengths were the same as 211.67 mm. The real size vs. the rendered VRML surface size was approximately the ratio of 1 to 605.9. A VRML measuring tool was made and merged with previous VRML surfaces. User interface tools were embedded with Java Script routines to display MRI planar images as cross sections of 3D surface models and to set transparencies of 3D surface models. When transparencies of 3D surface models were properly controlled, a fused display of the brain geometry with 3D distributions of focal activated regions provided intuitively spatial correlations among three 3D surface models. The epileptic seizure focus was in the right temporal lobe of the brain. The real position of the seizure focus could be verified by the VRML measuring tool and the anatomy corresponding to the seizure focus could be confirmed by MRI planar images crossing 3D surface models. The VRML application developed in this study may have several advantages. Firstly, 3D fused display and control of anatomic and functional image were achieved on the m. Secondly, the vector analysis of a 3D surface model was defined by the VRML measuring tool based on the real size. Finally, the anatomy corresponding to the seizure focus was intuitively detected by correlations with MRI images. Our web based visualization of 3-D fusion image and its localization will be a help to online research and education in diagnostic radiology, therapeutic radiology, and surgery applications.