• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.421-423
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• 2003

3D 가상환경 개발 초기 단계에서부터 효과적인 Navigation을 위해서 Navigation Aid에 대한 연구가 꾸준히 진행되어왔다. 그러나 지금까지는 환경 구조의 중요 지점만을 정리한 요약 형태의 정보를 제공하는 방법이 주를 이루고 있어서, Navigation 대상 환경에 익숙지 않은 사용자에게 환경구조를 이해하게 하는 인지적 부담을 주고 있다. 본 논문에서는 사용자의 Navigation을 위한 인지적 부담을 최소화 하는 토픽맵을 적용한 투어코스 자동생성 및 생성보조 시스템을 본 Navigation Aid 시스템이 적용된 가상 환경을 통해서 제안했다. 이는 현실세계에 존재하는 환경을 가상환경을 통해 사전방문 하거나 효과적인 이동경로를 선정하는데 도움을 줄 수 있을 것으로 기대한다.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.696-699
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• 2004

본 논문은 현실감 있는 영상 기반 환경 모델의 생성을 위해 영상 분할 기반 환경 모델링 방법을 제안한다. 입력 영상을 환경 특성에 따라 바닥면, 천정(하늘), 주변 물체들로 분할하고 분할된 바닥면이나 천정을 참조 평면으로 설정하고 주변 물체들의 깊이값을 계산함으로써 상세한 환경 모델을 얻을 수 있다. 영상 분할 환경 모델링 방법은 환경 맵에 적용하기 용이하며 환경의 특성에 따른 깊이값 추출 방법으로 손쉽게 환경 모델링이 가능하다. 또한, 시점이 이동되고 시차를 갖는 환경의 표현이 가능하다.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.228-237
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• 2007

displacement mapping enables us to add realistic details to polygonal meshes without changing geometry. We present a real-time artifacts-free inverse displacement mapping method. In each pixel, we construct a ray and trace the ray through the displacement map to find an intersection. To skip empty regions safely, we traverse the image pyramid of displacement map in top-down order. Furthermore, when the displacement map is enlarged, intersection with bilinear interpolated displacement map can be found. When the displacement map is at distance, our method supports mipmap-like prefiltering to enhance image quality and speed. Experimental results show that our method can produce correct images even at grazing view angles. Rendering speed of a test scene is over hundreds of frames per second and the influence of resolution of displacement map to rendering speed is little. Our method is simple enough to be added to existing virtual reality systems easily.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.3
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• pp.190-195
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• 2016

A technology is continuously developed in a rapidly changing global market. A company requires an appropriate R&D strategy for adapting to this environment. That is, the technologies owned by the company needs to be thoroughly analyzed to improve its competitiveness. Alternatively, technology classification using IPC codes is carried out recently in an objective and quantitative way. International Patent Classification, IPC is an internationally specified classification system, so it is helpful to conduct an objective and quantitative patent analysis of technology. In this study, all of the patents owned by company C are investigated and a matrix representing IPC codes of each patent is created. Then, a structured association map of the patents is made through association rules mining based on Confidence. The association map can be used to inspect the current situation of a company about patents. It also allows highly associated technologies to be clustered. Using the association map, this study analyzes the technologies of company C and how it changes with time. The strategy for future technologies is established based on the result.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.1-11
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• 2004

In this paper. we propose a storage system for XML documents using relational databases. Additional processing is required to store XML documents in the relational databases due to the discrepancy between XML structures and relational schema. This study aims to store XML documents with DTD in the relational databases. We propose the association inlining that exploits shred inlining and hybrid inlining and avoids relation fragments and excessive joins. Experiments show some improvements in the performance with the proposed method. The information of the storage structures is extracted from the simplified DTD. Existing map classes are extended in order to map various structures of XML to relational schema. Map classes are defined for various structures such as elements with multiple values, elements with multiple super elements, and elements with recursive structures through analyzing XML documents. Map files that are XML structures and used in generating SQL statements are created by using the extracted information of storage structures and map classes.

• Journal of Korea Game Society
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• v.7 no.4
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• pp.53-62
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• 2007

Although radiosity can represent diffuse reflections of the object surfaces by modeling energy exchange in 3D space, there are some restrictions for real-time applications because of its computation loads. Therefore, GPU(Graphics Processing Unit) based radiosity algorithms have been presented actively to improve its rendering performance. We implement the progressive refinement radiosity on GPU by G. Coombe in 3D scene that is constructed with HDR(High Dynamic Range) radiance map. This radiosity method can generate a photo-realistic rendering image in 3D space, where the synthetic objects were illuminated by the environmental light sources. In the simulation results, the rendering performance is analyzed according to the resolution of the texel in the environmental map and mipmaping. In addition, we compare the rendering results by our method with those by the incremental radiosity.

• Journal of KIISE:Databases
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• v.29 no.5
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• pp.358-366
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• 2002

Feature-based similarity retrieval become an important research issue in image database systems. The features of image data are useful to discrimination of images. In this paper, we propose the high speed k-Nearest Neighbor search algorithm based on Self-Organizing Maps. Self-Organizing Maps(SOM) provides a mapping from high dimensional feature vectors onto a two-dimensional space and generates a topological feature map. A topological feature map preserves the mutual relations (similarities) in feature spaces of input data, and clusters mutually similar feature vectors in a neighboring nodes. Therefore each node of the topological feature map holds a node vector and similar images that is closest to each node vector. We implemented a k-NN search for similar image classification as to (1) access to topological feature map, and (2) apply to pruning strategy of high speed search. We experiment on the performance of our algorithm using color feature vectors extracted from images. Promising results have been obtained in experiments.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.11
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• pp.529-536
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• 2015

When rendering both three-dimensional objects and photo images together, the non-photorealistic rendering results are in visual discord since the two contents have their own independent color distributions. This paper proposes a non-photorealistic rendering technique which renders both three-dimensional objects and photo images such as cartoons and sketches. The proposed technique computes the color distribution property of the photo images and reduces the number of colors of both photo images and 3D objects. NPR is performed based on the reduced colormaps and edge features. To enhance the natural scene presentation, the image region segmentation process is preferred when extracting and applying colormaps. However, the image segmentation technique needs a lot of computational operations. It takes a long time for non-photorealistic rendering for large size frames. To speed up the time-consuming segmentation procedure, we use GPGPU for the parallel computing using the GPU. As a result, we significantly improve the execution speed of the algorithm.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.1
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• pp.9-20
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• 2005

Recently, the MPEG-7 standard a multimedia content description standard is wide]y used for content based image/video retrieval systems. However, since the descriptors standardized in MPEG-7 are usually multidimensional and the problem called 'Curse of dimensionality', previously proposed indexing methods(for example, multidimensional indexing methods, dimensionality reduction methods, filtering methods, and so on) could not be used to effectively index the multimedia database represented in MPEG-7. This paper proposes an efficient multimedia data indexing mechanism reflecting the characteristics of MPEG-7 visual descriptors. In the proposed indexing mechanism, the descriptor is transformed into a histogram of some attributes. By representing the value of each bin as a binary number, the histogram itself that is a visual descriptor for the object in multimedia database could be represented as a bit string. Bit strings for all objects in multimedia database are collected to form an index file, bitmap index, in the proposed indexing mechanism. By XORing them with the descriptors for query object, the candidate solutions for similarity search could be computed easily and they are checked again with query object to precisely compute the similarity with exact metric such as Ll-norm. These indexing and searching mechanisms are efficient because the filtering process is performed by simple bit-operation and it reduces the search space dramatically. Upon experimental results with more than 100,000 real images, the proposed indexing and searching mechanisms are about IS times faster than the sequential searching with more than 90% accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.241-242
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• 2012