• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.535-540
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• 2006

집적 영상(Integral Imaging) 시스템은 관찰자가 특수안경의 착용 없이 육안으로 3 차원 영상을 볼 수 있는 무안경식 양안시차 디스플레이 방식 중 하나로, 수직, 수평 시차와 총천연색의 영상을 제공한다. 집적영상 시스템은 3 차원 정보를 2 차원 엘리멘탈 이미지 (Elemental image)의 형태로 저장하는데, 엘리멘탈 이미지는 조금씩 다른 방향에서 제한된 크기로 촬영된 이미지이다. 엘리멘탈 이미지는 컴퓨터 그래픽으로 만들어질 수도 있는데, 이를 이용하는 집적 영상 방식을 CG 직접 영상 시스템이라 한다. 이와 같이 컴퓨터 계산에 의해 엘리멘탈 이미지를 얻는 과정을 이미지 매핑 (Image mapping)이라 부른다. 이제까지 제안된 이미지 매핑 방식에는 점대점 (Point to Point), MVR (Multi-Viewpoint Rendering), PGR (Parallel Group Rendering) 이 있다. 그러나 이런 방식들은 계산량이 많거나 렌즈 어레이 개수의 증가에 의해 속도에 영향을 받는 단점이 있어, 아직 가상현실 같은 실시간 CG 응용 분야에 사용하기 어려운 문제가 있다. 본 논문에서는 VVR (Viewpoint Vector Rendering)이라는 기존의 방법과 비교해 향상된 새로운 이미지 매핑 방법을 제안한다. 먼저 VVR 개념을 자세히 설명한 후 VVR 을 사용한 집적 영상 시스템을 구현하여 MVR 방법과 비교 분석한 실험결과와 개선되어야 할 방향을 제시한다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.11
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• pp.105-113
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• 2004

This paper proposes 3D graphics accelerator, especially rendering unit, for portable devices. The existing 3D architecture is not suitable for portable devices because of its huge size. To reduce the size, we use iterative architecture and fixed-point calculation. In this paper, we suggest the format of fixed-point comparing with the result images, and some special technique to control. Finally, it is implemented with FPGA and 0.25um ASIC technology respectively. The ASIC chip can execute 47.88M pixels per second. The size of ASIC chip is 4.9287mm*4.9847mm and the power consumption is 263.7mW with 50MHz operation frequency.

• 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.

• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.9-17
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• 2012

Recently, a new image appearance model, named iCAM06, was developed for High-Dynamic-Range (HDR) image rendering. The dynamic range of a HDR image needs to be mapped on the range of output devices, which is called the tone reproduction or tone mapping. The iCAM06, the representative HDR rendering algorithm also uses the tone compression using a S-curve mapping function for image reproduction on the dynamic range of output devices. However the iCAM06 occurs white point shift during its tone compression process. Therefore, we propose a compensation method for white point shift problem using the corrected channel gain function. Experiment results show that the proposed method has better performance than the iCAM06.

• Journal of the Korea Computer Graphics Society
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• v.29 no.3
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• pp.93-103
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• 2023

The problem of reconstructing three-dimensional models of people and objects from color and depth images captured by low-cost RGB-D cameras has long been an active research area in computer graphics. Color and depth images captured by low-cost RGB-D cameras are represented as point clouds in three-dimensional space, which correspond to discrete values in a continuous three-dimensional space and require additional surface reconstruction compared to rendering using polygonal models. In this paper, we propose an effective ray-tracing based technique for visualizing point clouds rather than polygonal models. In particular, our method shows the possibility of an effective rendering method even in mobile environment which has limited performance due to processor heat and lack of battery.

• Journal of Broadcast Engineering
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• v.26 no.3
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• pp.258-268
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• 2021

Point cloud content is immersive content that represents real-world objects with three-dimensional (3D) points. In the process of acquiring point cloud data or encoding and decoding point cloud data, the resolution of point cloud content could be degraded. In this paper, we propose a method of progressively enhancing the resolution of sequential point cloud contents through inter-frame registration. To register a point cloud, the iterative closest point (ICP) algorithm is commonly used. Existing ICP algorithms can transform rigid bodies, but there is a disadvantage that transformation is not possible for non-rigid bodies having motion vectors in different directions locally, such as point cloud content. We overcome the limitations of the existing ICP-based method by registering regions with motion vectors in different directions locally between the point cloud content of the current frame and the previous frame. In this manner, the resolution of the point cloud content with geometric movement is enhanced through the process of registering points between frames. We provide four different point cloud content that has been enhanced with our method in the experiment.

• International Journal of CAD/CAM
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• v.8 no.1
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• pp.41-44
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• 2009

This paper describes an implementation of virtual teeth modeling for a haptic dental simulation. The system allows dental students to practice dental procedures with realistic tactual feelings. The system requires fast and stable haptic rendering and volume modeling techniques working on the virtual tooth. In our implementation, a volumetric implicit surface is used for intuitive shape modification without topological constraints and haptic rendering. The volumetric implicit surface is generated from input geometric model by using a closest point transformation algorithm. And for visual rendering, we apply an adaptive polygonization method to convert volumetric teeth model to geometric model. We improve our previous system using new octree design to save memory requirement while increase the performance and visual quality.

• ETRI Journal
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• v.34 no.5
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• pp.791-794
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• 2012

We propose an efficient framework to realistically render 3D faces with a reduced set of points. First, a robust active appearance model is presented to detect facial features in the projected faces under different illumination conditions. Then, an adaptive simplification of 3D faces is proposed to reduce the number of points, yet preserve the detected facial features. Finally, the point model is rendered directly, without such additional processing as parameterization of skin texture. This fully automatic framework is very effective in rendering massive facial data on mobile devices.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.2
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• pp.84-93
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• 2008

Modeling and rendering of cloth texture have been regarded as one of the most important factors to enhance reality of the contents in the digital contents industry. So far, however, two major approaches to realistically describe the cloth texture were developed: building analytical reflectance model for target cloth and sometimes thread itself and obtaining overall reflectance model using optical equipments. However, yielding a plausible analytic reflection model satisfying many subtle characteristics of a cloth is not an easy task; moreover, fine-detailed modeling of the cloth pattern across the target clothes should also be accompanied by huge amount of computation. The method to obtain overall reflectance model needs expensive measurement equipments and data size becomes huge. Since it applies in the end the reflectance model obtained at one point of a cloth to across whole the visible area of the target clothes, it cannot properly reproduce the pattern of the clothes nor the texture. To address the aforementioned problems, this paper proposes a simple low cost camera rig and a novel method for realistic modeling and rendering of the cloth texture by analyzing photos taken by the proposed camera rig, which can reproduce even the texture pattern applied to the whole clothes, overcoming the one-point reflectance model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.106-109
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• 2000

The virtual reality - haptic device is developed for the purpose used in the work that human cannot approach and that need elaborate exercises. To render haptic, the total system is constituted master, haptic device, and slave, remote manipulator. Human operates the remote manipulator. Human operates the remote manipulator relying on the hapti devices and stereo graphic. And then the force and scene of the remote manipulator is fed-back from each haptic devices and virtual devices. The feedback information gets system gain exactly. The system gain provides the most exact haptic and virtual devices. The feedback information gets system gain exactly. The system gain provides the most exact haptic and scene to human by the location, the graphic rendering and the haptic rendering algorithm on real-time. In this research, 3D haptic device is developed for common usage and make human feel the haptic when human contacts virtual object rendered by computer graphic. The haptic device is good for tracing location and producing devices because of the row structure. Also, openGL and Visual Basic is utilized to the algorithms for haptic rendering. The haptic device of this research makes the interface possible not only with virtual reality but also with the real remote manipulator.