• 정보처리학회논문지A
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• 제9A권4호
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• pp.581-588
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• 2002

대화적인 멀티미디어 시스템 구현에 있어, 실시간 가시화/시각화(visualization)는 중요한 기능을 한다. 된 논문은 실시간 지형 렌더링을 위한 효율적인 자료 구조와 알고리즘을 제안한다. 대개의 경우, 지형 데이터는 매우 방대한 크기를 가지고 있어서 있는 데이터를 그대로 실시간 렌더링하는 것은 불가능할 경우가 많다. 따라서 실시간 지형 렌더링에서는 LOD(Levels of Detail) 관리와 뷰 프러스텀 컬링이 핵심 사항이 된다. 본 논문은 계층적이면서도 간결한 지형 자료 구조, 신속한 뷰 프러스텀 컬링, 효율적인 LOD 구축 및 이에 기반한 렌더링 기법을 상세히 기술한다. 실험 결과, 제안된 기법은 일반 PC 사양에서 초당 22 프레임의 렌더링 속도를 보였다.

• 한국측량학회지
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• 제35권2호
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• pp.103-112
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• 2017

Due to the large size and high complexity of modern buildings, the interest and the studies about indoor spatial information are increasing. Previous studies related to indoor spatial information were mostly about relevant technologies, and the application of indoor spatial information has been less studied. In the present study, the public administrative work areas where indoor spatial information may be applied were identified by using a modified delphi technique. And the indoor LOD (Level of Detail) and indoor positioning accuracy for indoor spatial information applications considering user requirements was established as standards for efficiently establishing and providing services. The required LOD and positioning accuracy for services was established by reestablishing indoor LOD and positioning accuracy and classifying services with reference to those. The indoor LOD was reestablished from LOD 0 to 4 by focusing on service utilization and general recognition, and the positioning accuracy was reestablished in three levels by considering the accuracy of the present positioning technology and service utilization status.

• 한국정보처리학회논문지
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• 제7권3호
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• pp.766-775
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• 2000

Representing 3-D objects with LOD requires a set of appropriate meshes according to the detail requirements. We have developed a system for improved geometry model data transmission and management by having only the wavelet coefficienets of the model corresponding to the detail levels, instead of generation all the meshes through wavelet transformation, when generating multiresolution meshes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.828-831
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• 2005

In feature-based multi-resolution modeling, the features are rearranged according to a criterion for the levels of detail (LOD) of multi-resolution models. In this paper, two different LOD criteria are investigated and discussed. The one is the volumes of subtractive features, together with the precedence of additive features over subtractive features. The other is the volumes of features, regardless of whether the feature types are subtractive or additive. In addition, the algorithms to define and extract the LOD models based on the criteria are also described. The criterion of the volumes of features can be used for a wide range of applications in CAD and CAE in virtue of its generality.

• 한국CDE학회논문집
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• 제10권6호
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• pp.444-454
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• 2005

Recently, the requirements of multi-resolution models of a solid model, which represent an object at multiple levels of feature detail, are increasing for engineering tasks such as analysis, network-based collaborative design, and virtual prototyping and manufacturing. The research on this area has focused on several topics: topological frameworks for representing multi-resolution solid models, criteria for the level of detail (LOD), and generation of valid models after rearrangement of features. As a solution to the feature rearrangement problem, the new concept of the effective zone of a feature is introduced in the former part of the paper. In this paper, we propose a feature-based non-manifold modeling system to provide multi-resolution models of a feature-based solid or non-manifold model on the basis of the effective feature zones. To facilitate the implementation, we introduce the class of the multi-resolution feature whose attributes contain all necessary information to build a multi-resolution solid model and extract LOD models from it. In addition, two methods are introduced to accelerate the extraction of LOD models from the multi-resolution modeling database: the one is using an NMT model, known as a merged set, to represent multi-resolution models, and the other is storing differences between adjacent LOD models to accelerate the transition to the other LOD. We also suggest the volume of the feature, regardless of feature type, as a criterion for the LOD. This criterion can be used in a wide range of applications, since there is no distinction between additive and subtractive features unlike the previous method.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2002년도 추계학술대회 논문집
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• pp.163-170
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• 2002

Terrain surfaces have to be modeled in very detail and wheel-surface contacting geometry must be well defined in order to obtain proper ground-reaction and friction forces for realistic simulation of off-road vehicles. Delaunay triangulation is one of the most widely used methods in modeling 3-dimensional terrain surfaces, and T-search is a relevant algorithm for searching resulting triangular polygons. The T-search method searches polygons in successive order and may not allow real-time computation of off-road vehicle dynamics if the terrain is modeled with many polygons, depending on the computer performance used in the simulation. In order to accelerate the searching speed of T-search, a terrain database of triangular polygons is modeled in multi-levels by adopting the LOD (Level of Detail) method used in realtime computer graphics. Simulation results show that the new LOD search is effective in shortening the required computing time. The LOD search can be even further accelerated by introducing an NN (Neural Network) algorithm, in the cases where a appropriate range of moving paths can be predicted by cultual information of the simulated terrain, such as lakes, houses, etc.. Numerical tests show that LOD-NN search almost double the speed of the original T-search.

• 한국기계가공학회지
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• 제19권7호
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• pp.22-34
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• 2020

Three-dimensional (3D) computer-aided design (CAD) models require different levels of detail (LODs) depending on their purpose. Therefore, it is beneficial to automatically simplify 3D CAD assembly models to meet the desired LOD. Feature-based 3D CAD assembly models typically have the lowest and highest feasible limits of LOD during simplification. In order to help users obtain a feasible simplification result, we propose a method to simplify feature-based 3D CAD assembly models by determining the lowest and highest limits of LOD. The proposed method is verified through experiments using a simplification prototype implemented as a plug-in type module on Siemens NX.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.549-557
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• 2005

The requirements of multi-resolution models of feature-based solids, which represent an object at many levels of feature detail, are increasing for engineering purposes, such as analysis, network-based collaborative design, virtual prototyping and manufacturing. To provide multi-resolution models for various applications, it is essential to generate adequate solid models at varying levels of detail (LOD) after feature rearrangement, based on the LOD criteria. However, the non-commutative property of the union and subtraction Boolean operations is a severe obstacle to arbitrary feature rearrangement. To solve this problem we propose history-based Boolean operations that satisfy the commutative law between union and subtraction operations by considering the history of the Boolean operations. Because these operations guarantee the same resulting shape as the original and reasonable shapes at the intermediate LODs for an arbitrary rearrangement of its features, various LOD criteria can be applied for multi-resolution modeling in different applications.

• 한국컴퓨터그래픽스학회논문지
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• 제13권3호
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• pp.19-24
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• 2007

본 논문에서는 가상환경의 물체들을 정확하게 비교하기 위하여 실세계 모든 길이 단위를 이용하여 물체의 길이를 정의하는 방법을 기술한다. 본 연구에서 브라우저는 화면상에 물체를 보여줄 때 모델러가 정의한 물리적 길이 속성을 참조하여 제작자가 원하는 길이로 물체를 표현한다. 서로 다른 모델러에서 제작된 서로 관계없는 물체들이라도 길이 명세를 가지고 있으면 브라우저에 들어 올 때 그에 따라 스케일이 적용되어 정확한 크기 비교가 가능하게 된다. 본 논문에서의 길이 명세는 X3D 명세에 추가하여 정의되었으며 포함되는 길이 단위는 $10^{-24}(yotta)$부터 $10^{24}(yocto)$ 까지이다. 그리고 서로 다른 LOLD(Levels of Length Detail) 속성을 가진 물체를 동시에 불러 올 때의 LOD(Levels of Detail) 처리와 LOLD 속성을 적용하는 방법에 대해 기술한다.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.558-566
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• 2005

We propose a feature-based multi-resolution representation of B-rep solid models using history-based Boolean operations based on the merge-and-select algorithm. Because union and subtraction are commutative in the history-based Boolean operations, the integrity of the models at various levels of detail (LOD) is guaranteed for the reordered features regardless of whether the features are subtractive or additive. The multi-resolution solid representation proposed in this paper includes a non-manifold topological merged-set model of all feature primitives as well as a feature-modeling tree reordered consistently with a given LOD criterion. As a result, a B-rep solid model for a given LOD can be provided quickly, because the boundary of the model is evaluated without any geometric calculation and extracted from the merged set by selecting the entities contributing to the LOD model shape.