• Journal of the Korea Society of Computer and Information
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• v.11 no.6 s.44
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• pp.269-277
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• 2006

We propose a new expert system for recovering the broken fragments of relics into an original form using computer graphics and image processing. This paper presents a system with an application to tombstones objects of flat plane with letters carved in for assembling the fragments by placing their respective fragments in the right position. The matching process contains three sub-processes: aligning the front and letters of an object, identifying the matching directions, and determining the detailed matching positions. We apply least squares fitting, vector inner product, and geometric and RGB errors to the matching process. It turned out that 2-D translations via fragments-alignment enable us to save the computational load significantly. Based on experimental results from the damaged cultural fragments, the performance of the proposed method is illustrated.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.1
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• pp.82-97
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• 1999

3차원 그래픽 렌더링은 화면상의 각 화소에 대하여 색깔뿐만 아니라 깊이 정보가지 계산해야 하기 때문에 방대한 계산량과 메모리 접근, 그리고 데이터 전송량을 필요로 하기 때문이다. 따라서 실시간 3차원 그래픽 처리를 위해서 병렬 처리 기법을 도입한다. 그러나 기존 그래픽 가속엔진은 병렬처리 기법으로 영상-병렬성을 이용한 화면 분할 방식을 사용하기 때문에 크게 두 가지 단점이 발생한다. 첫 번재는 화면 영역의 경게에 위치하는 다각형들에 대한 중복계산이고, 두 번째는 낮은 PE(Processing Element) 활용도이다. 본 논문에서는 이러한 문제를 해결하기 위한 방법으로 객체 기반 렌더링(OBR : Object Based Rendering)방식을 바탕으로 하는 그래픽 가속엔진을 제안하였다. OBR 시스템의 목적은 화면 분할 방식의 불필요한 오버헤드를 제거하여 수행 성능을 높이고, 자원을 효율적으로 사용하여 하드웨어 구성비용을 줄이는 것이다. 본 논문에서는 시뮬레이션을 통하여 OBR 시스템이 화면 분할 방식의 대표적인 그래픽 가속기인 PixelFlow와의 성능을 상대적으로 비교하였다. 결론적으로 OBR 시스템은 화면 분할 방식보다 더 적은 하드웨어 자원으로 보다 효율적으로 렌더링을 수해하였다.

• Journal of Korea Multimedia Society
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• v.14 no.8
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• pp.1082-1093
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• 2011

Traditional rendering of cartoon character cannot revive the feeling of concept drawings properly. In this paper, we propose capture technology to get toon shading model from the concept drawings and with this technique, we provide a new novel system to render 3D cartoon character. Benefits of this system is to cartoonize the 3D character according to saliency to emphasize the form of 3D character and further support the sketch-based user interface for artists to edit shading by post-production. For this, we generate texture automatically by RGB color sorting algorithm to analyze color distribution and rates of selected region. In the cartoon rendering process, we use saliency as a measure to determine visual importance of each area of 3d mesh and we provide a novel cartoon rendering algorithm based on the saliency of 3D mesh. For the fine adjustments of shading style, we propose a user interface that allow the artists to freely add and delete shading to a 3D model. Finally, this paper shows the usefulness of the proposed system through user evaluation.

• Journal of Broadcast Engineering
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• v.16 no.4
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• pp.596-601
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• 2011

In this paper, we propose a fast depth-image-based rendering method to generate a virtual view image in real-time using a graphic processor unit (GPU) for a 3D broadcasting system. Before the transmission, we encode the input 2D+depth video using the H.264 coding standard. At the receiver, we decode the received bitstream and generate a stereo video using a GPU which can compute in parallel. In this paper, we apply a simple and efficient hole filling method to reduce the decoder complexity and reduce hole filling errors. Besides, we design a vertical parallel structure for a forward mapping process to take advantage of the single instruction multiple thread structure of GPU. We also utilize high speed GPU memories to boost the computation speed. As a result, we can generate virtual view images 15 times faster than the case of CPU-based processing.

• The KIPS Transactions:PartB
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• v.17B no.3
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• pp.183-188
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• 2010

A factorization-based 3D reconstruction system is realized to recover 3D scene from an image sequence. The image sequence is captured from uncalibrated perspective camera from several views. Many matched feature points over all images are obtained by feature tracking method. Then, these data are supplied to the 3D reconstruction module to obtain the projective reconstruction. Projective reconstruction is converted to Euclidean reconstruction by enforcing several metric constraints. After many triangular meshes are obtained, realistic reconstruction of 3D models are finished by texture mapping. The developed system is implemented in C++, and Qt library is used to implement the system user interface. OpenGL graphics library is used to realize the texture mapping routine and the model visualization program. Experimental results using synthetic and real image data are included to demonstrate the effectiveness of the developed system.

• Journal of the Korea Computer Graphics Society
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• v.3 no.2
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• pp.27-34
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• 1997

3-D image modeling is in high demand for automated visual inspection and non-destructive testing. It also can be useful in biomedical research, medical therapy, surgery planning, and simulation of critical surgery (i.e. cranio-facial). Image processing and image analysis are used to enhance and classify medical volumetric data. Analyzing medical volumetric data is very difficult In this paper, we propose a new image modeling method based on tetrahedrization to improve the visualization of three-dimensional medical volumetric data. In this method, the trivariate piecewise linear interpolation is applied through the constructed tetrahedral domain. Also, visualization methods including iso-surface, color contouring, and slicing are discussed. This method can be useful to the correct and speedy analysis of medical volumetric data, because it doesn't have the ambiguity problem of Marching Cubes algorithm and achieves the data reduction. We expect to compensate the degradation of an accuracy by using an adaptive sub-division of tetrahedrization based on least squares fitting.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.59-66
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• 2001

Networked Virtual Reality systems provide a consistent virtual world to the users, possibly ditributed across long distance, and have been widely applied in the military war game, network game. edutainment, architectural areas, and shopping mall etc. Large processing requirements. however. made these systems be mainly researched on the platforms of high-performence system graphics workstations. This study paper Presents several problems when networked virtual reality systems are implemented on commodity Internet : two problems related with 3D graphical Processing, and the other related with network bandwidth and transmission delay. We also suggest solutions to these problems and analyze their performance effect based on an architectural simulation application.

• The KIPS Transactions:PartA
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• v.15A no.1
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• pp.1-8
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• 2008

An occlusion culling method, one of visibility culling methods, excludes invisible objects or triangles which are covered by other objects. As it reduces computation quantity, occlusion culling is an effective method to handle complex scenes in real-time. But an existing common occlusion culling method, such as hardware occlusion query method, sends objects' data twice to GPU and this causes processing overheads once for occlusion culling test and the other is for rendering. And another existing hardware occlusion culling method, VCBP, can test objects' visibility quickly, but it neither test bounding volume nor return test result to application stage. In this paper, we propose a single pass occlusion culling method which uses temporal and spatial coherency, with effective occlusion culling hardware architecture. In our approach, the hardware performs occlusion culling test rapidly with cache on the rasterization stage where triangles are transformed into fragments. At the same time, hardware sends each primitive's visibility information to application stage. As a result, the application stage reduces data transmission quantity by excluding covered objects using the visibility information on previous frame and hierarchical spatial tree. Our proposed method improved maximum 44%, minimum 14% compared with S&W method based on hardware occlusion query. And the performance is increased 25% and 17% respectively, compared to maximum and minimum performance of CHC method which is based on occlusion culling method.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.4
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• pp.125-128
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• 2014

OpenGL ES(OpenGL for Embedded System) 2.0 is one of the most widely used 3D graphics API(application progrma interface) standard for smart phones and tablet PCs at this time. During programming with this API, they prefer desktop environment rather than the target mobile environment, which has relatively low computing power. Thus, we need to emulate the OpenGL ES 2.0 API on the desktop PCs, where only OpenGL API libraries are available. In this paper, we present technical difficulties and their solutions to emulate OpenGL ES 2.0 on desktop PCs. Our final implementation of OpenGL ES 2.0 emulation library works on desktop PCs and passed over more than 96% of the official CTS(conformance test suites) to prove the correctness of our implementation. Additionally, for the commercially available benchmark programs, our implementation shows equivalent execution speeds to the previous commercial OpenGL ES 2.0 implementations.

• Journal of the Korea Computer Graphics Society
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• v.23 no.3
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• pp.65-75
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• 2017

As a 360-degree image carries information of all directions, it often has too much information. Moreover, in order to investigate a 360-degree image on a 2D display, a user has to either click and drag the image with a mouse, or project it to a 2D panorama image, which inevitably introduces severe distortions. In consequence, investigating a 360-degree image and finding an object of interest in such a 360-degree image could be a tedious task. To resolve this issue, this paper proposes a method to find a region of interest and produces a 2D naturally looking image from a given 360-degree image that best matches a description given by a user in a natural language sentence. Our method also considers photo composition so that the resulting image is aesthetically pleasing. Our method first converts a 360-degree image to a 2D cubemap. As objects in a 360-degree image may appear distorted or split into multiple pieces in a typical cubemap, leading to failure of detection of such objects, we introduce a modified cubemap. Then our method applies a Long Short Term Memory (LSTM) network based object detection method to find a region of interest with a given natural language sentence. Finally, our method produces an image that contains the detected region, and also has aesthetically pleasing composition.