• Journal of Korea Game Society
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• v.11 no.1
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• pp.131-138
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• 2011

Recently in terrain rendeing, most researches introduce mipmap-based out-of-core methods for handling large sized DEM data which does not fit in main memory of general computer. However, mipmap-based LOD(level-of-detail) methods occur geometric errors which appear in data simplifying the higher LOD level. These geometric errors cause geometric popping effects where LOD level changes when viewpoint moves. In this paper, we propose vertex cohesion map for reducing geometric error. In preprocessing step, we generate vertex cohesion map, which is a texture that stores the vectors. By these vectors, each vertex will be cohered into the position in which the difference of gradient value is bigger than others. Therefore in terrain rendering, using vertex cohesion map can dramatically reduce the geometry popping effects rather than using mipmap.

• Journal of KIBIM
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• v.3 no.1
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• pp.1-10
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• 2013

BIM(Building Information Modeling) ordering manuals and guidelines are diffused with the recent BIM activation. However, it is causing drawbacks such as an increase of work at each design stage and a decline of BIM application level that the standard of making up and managing BIM is vague and it includes comprehensive meaning. Therefore, this study aims to secure BIM work standard by establishing BIM making-out standard based on LOD(Level of Detail) classification considering domestic design process. It compared each definition of LOD by analyzing domestic and foreign BIM guideline examples, and figured out insufficiency of existing domestic and foreign design process and BIM guidelines. Moreover, it drew architects' work articles for promoting the progression of the efficient design process, and analyzed BIM requirements on design process, dividing BIM application scale by field. Through this analyzing process, it finally established BIM making-out standard classified by design process. The effects of establishing BIM making-out standard would include improving a division of labor and cooperation environment by creating integrated BIM model on design stages, advancing work efficiency by preventing a repetition and an increase of work, and upgrading project completeness and design quality. Besides, it can secure BIM work standard by clarifying responsibility for working steps. BIM making-out standard established by this study will contribute to developing the future BIM work standard document and BIM guideline as a data base.

• Annual Conference of KIPS
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• 2007.05a
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• pp.333-336
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• 2007

We propose a simple method for tracking a nonparameterized subject contour in a single video stream with a moving camera and changing background. Then we present a method to eliminate the tracked contour object by replacing with the background scene we get from other frame. Our method consists of two parts: first we track the object using LOD (Level-of-Detail) canny edge maps, then we generate background of each image frame and replace the tracked object in a scene by a background image from other frame that is not occluded by the tracked object. Our tracking method is based on level-of-detail (LOD) modified Canny edge maps and graph-based routing operations on the LOD maps. To reduce side-effects because of irrelevant edges, we start our basic tracking by using strong Canny edges generated from large image intensity gradients of an input image. We get more edge pixels along LOD hierarchy. LOD Canny edge pixels become nodes in routing, and LOD values of adjacent edge pixels determine routing costs between the nodes. We find the best route to follow Canny edge pixels favoring stronger Canny edge pixels. Our accurate tracking is based on reducing effects from irrelevant edges by selecting the stronger edge pixels, thereby relying on the current frame edge pixel as much as possible. This approach is based on computing camera motion. Our experimental results show that our method works nice for moderate camera movement with small object shape changes.

• Journal of Korea Game Society
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• v.8 no.3
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• pp.61-68
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• 2008

Quadtree-based terrain visualization methods have been used in a lot of applications. However, because most procedures are performed on the CPU, the rendering speed is slow in comparison to methods using GPU. In this paper, we present a quadtree-based terrain visualization method working on the GPU with specially designed data structure, error-texture and LOD-texture, and block-based acceleration method. In preprocessing step, we calculate errors in world space and store them to error-texture. In rendering step, we examine projected errors of error-texture and choose the detail level, then store the projected errors to LOD-texture. View frustum culling is performed as block unit using the values of error-texture and LOD-texture. This method reduces CPU load and performs time consuming jobs such as LOD selection and view frustum culling.

• Korean Journal of Construction Engineering and Management
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• v.20 no.6
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• pp.89-97
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• 2019

Recently, BIM has been actively introduced in construction projects. In particular, the introduction of BIM in cost estimating process is expected to improve the accuracy and efficiency of the cost estimate. However, the quantity calculation and BoQ documents preparation process still require manual work. Although the BIM model may support quantification process, it is still problematic that the level of detail of the model must be very detailed to meet the items in BoQ. To address this, it is necessary to analyse the LOD criteria and to analyze the extent to which quantity can be computed according to the level of detail in the BIM model. For the analysis of LOD-based work items, the work item grades were divided into A,B, and C. In this study, the ratio and cost of each item that can be calculated at the LOD level in the detailed design phase are reviewed for each type of work, and the method for improving the quantity calculation using BIM is proposed. In the LOD 300 stage(Detailed design stage), the largest number of items in the class B, the major improvement class, are window and glass work. In addition, the most expensive type of work was analyzed by reinforced concrete work. In the future, it is necessary to suggest appropriate improvement way for items with high item ratios and items with high cost ratios. The results of this study are expected to be used as a BIM-based cost estimation or as basic data for improving the current BoQ system.

• Journal of the Korea Society for Simulation
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• v.10 no.3
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• pp.95-103
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• 2001

Rendering of 3D terrain data in real-time is difficult because of its large scale. So, it is necessary to use level-of-detail(LOD) that uses fewer data, but makes almost similar image to the original. We present an algorithm for real-time LOD generation and rendering of 3D terrain data. The algorithm applies wavelet transform to the terrain data, and then generates quadtree based view-dependent LOD using wavelet coefficients that are the output of wavelet transform. It also uses frame-to-frame coherence and view culling for high frame rates.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.586-588
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• 1999

간소화된 메쉬의 다중해상 표현은 실시간으로 원하는 해상 메쉬의 랜더링이 가능하고 저해상 메쉬에서 고해상 메쉬로의 전환이 시각적인 연속성을 갖는다. 또 메쉬의 공간마다 다른 해상도의 표현이 가능하다. 본 논문에서는 기존의 다중해상모델의 특징과 단점을 알아보고 다중모델링 이슈을 제시한다. 효율적인 가변 LOD를 위한 기존의 다중해상 모델을 일반화시킨 MT(MultiTriangulation)를 제시한다. MT의 구조적 특징, MT에서의 선택적 상세화와 시점과의 거리에 따른 가변 LOD 질의를 알아본다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.595-597
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• 1999

기존의 LOD 제어방법들은 랜더링속도를 성공적으로 증가시켜왔으나 오버헤드가 크다는 단점을 갖고 있다. 이러한 오버헤드는 각 vertex마다 view-frustum clipping, back-face culling, 스크린 공간 기하학적 오차계산과 같은 view-dependent refinement criteria를 측정하고, 메쉬의 LOD를 바꾸기 위해서 edge collapse/vertex split를 수행하기 때문이다. 제안하는 방법은 메쉬를 여러 개의 region들로 나누고 vertex가 아닌 region에 대해 view-dependent refinement criteria를 측정하므로 오버헤드가 훨씬 작다. 또한 각 region 들의 LOD가 바뀔 때 미리 만들어 둔 LOD 버전들중에서 하나를 선택하기만 하면 되므로, edge collapse/vertex split을 수행하는 오버헤드는 없다. 실험적으로 제안하는 LOD 제어방법은 기존의 방법들보다 작은 메모리를 사용하고 LOD 제어 오버헤드도 적으며, LOD 제어를 하지 않은 경우보다 2배-5배의 랜더링 속도향상을 얻었다.

• Spatial Information Research
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• v.21 no.5
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• pp.73-82
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• 2013

In recent years, according to the increase of interests in indoor space, various researches are being carried out for the construction and services of indoor spatial information. BIM data is very useful to build indoor spatial information. Accordingly, many studies for the use of BIM data on GIS part are in progress. In order to take advantage of BIM data on GIS part, the conversion technology for building indoor data and visualization techniques are required. However, most of the previous researches are focused on the conversion technology to construct indoor spatial information by importing BIM data into GIS applications while there is few research on visualization. In this study, an indoor LOD(Level of Detail) model is proposed to apply to on indoor facility management system when indoor data was constructed based on BIM data for the linkage between BIM and GIS.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.186-190
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• 2002

영상의 밝기로부터 표면의 높이를 효과적으로 재구성하기 위한 방안으로 먼저 DCT공간상에서 표면의 형태를 구성한다. 이렇게 구성된 표면형태에 대한 정보를 기초로 축소된 영상과 입력영상에 대해 단계별로 표면을 구성한다. 표면 재구성 과정에서 생성되는 물체의 대략적인 표면정보는 버려지지 않고 게임 등 실시간으로 빠르게 처리해야하는 그래픽을 제공하기 위한 LOD(Level of Detail) 정보를 구성한다. 멀리 있는 물체에 대한 빠른 렌더링을 위해 표면 재구성 초기에 구성된 LOD 메쉬정보를 이용하고 가까운 물체의 경우에는 세밀한 표면의 형태를 표현하는 LOD 메쉬를 사용함으로써 그래픽 처리의 효율을 높일 수 있게 된다.