• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1363-1368
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• 2016

Fast rendering speed is one of key functions to provide realistic scenes in flight simulator. However, since flight simulator mostly operates with high volume terrain data, rendering speed is reduced and changed very rapidly when it handles file containing too much vertexs. So, previous schemes make use of Level of Details (LOD) scheme to prevent this problem. But, since LOD is applied after the large number of vertexs are detected, transition between scenes is not completely smooth. To solve this problem, in this paper, we propose a new dynamic LOD scheme which controls LOD level in advance through prediction of vertex overload. To verify the proposed scheme, we implement the proposed scheme in our flight simulation through OpenSceneGraph(OSG) and identify the reduced number of vertexs and enhanced Frame Per Second (FPS) by comparing real data with predicted one.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.3
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• pp.199-209
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• 2009

In this paper, we suggest a stroke level of detail (LOD) based on a saliency density. On painter]y rendering, the stroke LOD has an advantage of making the observer concentrate on the main object and improving accuracy of expression. For the stroke LOD, it is necessary to classify the detailed and abstracted area. We divide the area on the basis of saliency distribution and the level of detailed expression is controlled based on the saliency information. 'We define that the area of which the saliency distribution is high is a major subject that an artist tries to express, it is described in detail. The area of which the saliency distribution is low is abstractly described. Each divided area has the abstraction level. And by adapting the brushes of which sizes are appropriate to each level, it is possible to express the area which needs to be expressed in details from the one which needs to be expressed abstractly.

• KIEAE Journal
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• v.15 no.6
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• pp.69-80
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• 2015

Purpose: Since most simulation programs take the interface that lists up all the input variables representing all the functionalities, users must know where design variables of an Energy Conservation Measure (ECM) are located and also know what values are appropriate. This is why practitioner designers feel frustrated when they attempt to use simulation. The final objective of this study is to provide a building energy modeling guideline for practitioners in various fields such as architectural design and MEP. Method: As the first step of the modeling guideline, this study provides the Level of Detail (LOD) for simulation modeling of primary ECMs considering the design information available in each design phase. It is prepared by literature review, simulation functionality investigation, and field experts' survey. Result: The proposed simulation LOD offers a milestone at each design phases concerning what design variable and attributes need to be developed with how much of details in order to meet the project goal. Also each design team can set up a simulation usecase considering organizational characteristics based on the proposed LOD.

• International Journal of CAD/CAM
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• v.8 no.1
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• pp.37-40
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• 2009

Based on the study of Digital Elevation Simplification Model and fractal theory, this paper put forward a new method to simulate complex terrain. That use simplified DEM data to construct terrain frame based on the quad tree at first, and then use fractal to generate the details of every node of the tree. In the process of construction, the LOD theory is used to simplify the terrain and get its typical data. According to the change of view position and direction, the paper gives a new way to judge the visibility of the surface patch. Experimental results show that this algorithm is simple, efficient and supports the real time dynamic simulation of terrain model.

• Journal of the Korea Society of Computer and Information
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• v.23 no.7
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• pp.57-62
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• 2018

In this paper, we propose an improved algorithm for rendering method to guarantee frame rates based on HMD (Head Mounted Display) motion in an avionics simulator. One of important issues in HMD simulators is to guarantee frame rates despite fast motion of HMD which is more rapid than the aircraft's moving speed to maintain a quality of images. Therefore, we propose an algorithm considering the moving speed of a pilot's head: Improved Speed-Based LOD (Level-Of-Detail) Control (ISBLC). In the proposed algorithm, frame rates are improved by changing dynamic LOD which determines details of objects for rendering images. Throughout the experiments, we show the average frame rates are achieved up to 60 and minimum frame rates are guaranteed up to 40. The proposed algorithms will be used HMD simulation in avionics simulators.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.353-356
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• 2000

최근 복잡한 실제 사물을 가상 공간상에 표현하기 위해 삼차원 모델을 많이 이용하고 있다. 기존의 삼차원 데이터 처리는 주로 정지 모델에 대해 기하학 정보와 위상학 정보를 표현하거나 다중 해상도(Level of Details, LOD)로 나타내는데 역점을 두었다. 그러나 네트웍을 통한 가상 공간에서 삼차원 애니메이션에 대한 응용이 점차 늘어남에 따라 이러한 데이터를 효율적으로 압축하여 전송하거나 저장할 필요가 생겼다 본 논문에서는 삼차원 애니메이션 모델의 공간적 또는 시간적 상관 관계를 이용하여 삼차원 모델 정보를 부호화하는 방법을 제안한다. 먼저 주어진 모델의 움직임을 분석하고 이를 (r,θ,ø)의 구 좌표계로 변환한 후 (θ,ø)의 분포에 따라 모델을 분할(Segmentation)한다. 그리고 움직임 벡터는 Affine 변환을 이용하여 삼차원 공간에서의 움직임을 정의한다. Key프레임에 해당하는 정지 모델의 기하학 정보와 위상학 정보를 압축하고, LOD 기술을 적용하여 손실 혹은 무손실로 부호화하여 전송한다. 또한 Key프레임 사이의 화면에서는 선형 또는 비선형 보간법으로 각 분할 부분을 복원하고, 이를 조합하여 전체적인 삼차원 모델을 복원한다.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.768-775
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• 2022

Current MEP designs are mostly applied by 2D-based design methods and tend to focus on simple modeling or geometry information expression such as converting 2D-written drawings into 3D modeling without taking advantage of the strength of BIM application. To increase the demand for BIM-based MEP design, geometric information, and property information of each member of the 3D model must be conveniently linked from the phase of the Design Development (DD) to the phase of Construction Document (CD). To conveniently implement a detailed model at each phase, the detailed level of each member of the 3D model must be specific, and an automatic generation of objects at each phase and automatic detailing module for each LOD are required. However, South Korea's guidelines have comprehensive standards for the degree of MEP modeling details for each design phase, and the application of each design phase is ambiguous. Furthermore, in practice, detailed levels of each phase are input manually. Therefore, this paper summarized the detailed standards of MEP modeling for each design phase through interviews with MEP design companies and related literature research. In addition, items that enable auto-detailing with DYNAMO were selected using the checklist for each design phase, and the types of detailed methods were presented. Auto-detailing items considering the detailed level of each phase were classified by members. If a DYNAMO algorithm is produced that automates selected auto-detailing items in this paper, the time and costs required for modeling construction will be reduced, and the demand for MEP design will increase.

• Journal of information and communication convergence engineering
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• v.9 no.3
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• pp.266-270
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• 2011

The advancement of technology enables smart phones or handheld devices to render complex 3D graphics. However, the processing power and memory of smart phones remain very limited to render high polygon and details 3D models especially on games which requires animation, physic engine, or augmented reality. In this paper, several techniques will be introduced to speed up the computation and reducing the number of vertices of the 3D meshes without losing much detail.

• IE interfaces
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• v.16 no.spc
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• pp.87-92
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• 2003

Progressive mesh representation and generation have become one of the most important issues in network-based computer graphics. However, current researches are mostly focused on triangular mesh models. On the other hand, solid models are widely used in industry and are applied to advanced applications such as product design and virtual assembly. Moreover, as the demand to share and transmit these solid models over the network is emerging, the generation and the transmission of progressive solid models depending on specific engineering needs and purpose are essential. In this paper, we present a Cellular Topology-based approach to generating and transmitting progressive solid models from a feature-based solid model for internet-based design and collaboration. The proposed approach introduces a new scheme for storing and transmitting solid models over the network. The Cellular Topology (CT) approach makes it possible to effectively generate progressive solid models and to efficiently transmit the models over the network with compact model size.

• Korean Journal of Computational Design and Engineering
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• v.18 no.1
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• pp.58-70
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• 2013

This study for establishing specific standards of atrium design aims to discuss design of atrium to consider energy performance atrium in office buildings. In order to evaluate a type and a scale of atrium at the early design stage, modeling details of mass design were set as standards of conceptual design. In the experiment, Project Vasari was used to analyze modeling and energy consumption, based on the LOD 100-step suggested by AIA, because there is no guideline to specify a level of modeling details at each design process. From this analysis, the correlation among a simple-typed atrium and scale and energy load was considered. The result of this research is as follows: First, the single-sided atrium reduced energy the most, and it was followed by three-sided, two-sided, four-sided and continuous-typed ones. On the whole, they could decrease energy by up to about 15%. Also, the atrium with a wide facade facing in the south was more favorable to reduce energy. Second, planning the atrium within 10~30% of the whole building area was more energy efficient. Third, rather than the depth, adjusting the length in designing an atrium could reduce cooling and heating loads by 1.5% per 1m. As explained above, energy performance evaluation considering types and planning elements of atrium helps to assess alternatives in a reasonable way. In particular, considering the use of building needs to be preceded to select a type of atrium, although it is also important to consider its planning elements.