• Korean Journal of Computational Design and Engineering
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• v.13 no.6
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• pp.469-477
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• 2008

Physically-based rendering is an image synthesis technique based on simulation of physical interactions between light and surface materials. Since generated images are highly photorealistic, physically-based rendering has become an indispensable tool in advanced design visualization for manufacturing and architecture as well as in film VFX and animations. Especially, BRDF (bidirectional reflectance distribution function) is critical in realistic visualization of materials since it models how an incoming light is reflected on the surface in terms of intensity and outgoing angles. In this paper, we introduce techniques to represent BRDF as B-spline volumes and to utilize them in physically-based rendering. We show that B-spline volume BRDF (BVB) representation is suitable for measured BRDFs due to its compact size without quality loss in rendering. Moreover, various CAGD techniques can be applied to B-spline volume BRDFs for further controls such as refinement and blending.

• Economic and Environmental Geology
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• v.50 no.3
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• pp.239-250
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• 2017

Physically based landslide susceptibility analysis has been recognized as an effective analysis method because it can consider the mechanism of landslide occurrence. The physically based analysis used the slope geometry and geotechnical properties of slope materials as input. However, when the physically based approach is adopted in regional scale area, the uncertainties were involved in the analysis procedure due to spatial variation and complex geological conditions, which causes inaccurate analysis results. Therefore, probabilistic method have been used to quantify these uncertainties. However, the uncertainties caused by lack of information are not dealt with the probabilistic analysis. Therefore, fuzzy set theory was adopted in this study because the fuzzy set theory is more effective to deal with uncertainties caused by lack of information. In addition, the vertex method and Monte Carlo simulation are coupled with the fuzzy approach. The proposed approach was used to evaluate the landslide susceptibility for a regional study area. In order to compare the analysis results of the proposed approach, Monte Carlo simulation as the probabilistic analysis and the deterministic analysis are used to analyze the landslide susceptibility for same study area. We found that Fuzzy Monte Carlo simulation showed the better prediction accuracy than the probabilistic analysis and the deterministic analysis.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.3
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• pp.147-156
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• 2006

Physically-based simulation modeling is to simulate the real world by using physical laws such as Newton's second law of motion, while other modelings use only geometric Properties. In this paper, we present a real time simulation of stone skipping by using the physically-based modeling. We also describe interaction of a stone on the surface of water, and focus on calculating the path of the stone and the natural phenomena of water The path is decided by velocity of the stone and drag force from the water The motion is recalculated until the stone is immersing into the water surface. Our simulation provides a natural motion of stone skippings in real time. And the motion of stone skippings are generated by give interactive displays on the PC platforms. The techniques presented can easily be extended to simulate other interactive dynamics systems.

• Journal of the Korea Society for Simulation
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• v.18 no.2
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• pp.57-64
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• 2009

Stable and effective constraint enforcement system is one of the crucial components for physically-based dynamic simulations. This paper presents analysis and evaluation for traditional constraint enforcement systems(Lagrange Multiplier method, Baumgarte stabilization method, Post-stabilization method, Implicit constraint enforcement method, Fast projection method) to provide a guideline to users who need to integrate a suitable constraint enforcement system into their dynamic simulations. The mathematical formulations for traditional constraint enforcement systems are presented in this paper. This paper describes a summary of evaluation which consists of constraint error comparison, computational cost, and dynamic behavior analysis to verify the efficiency of each traditional constraint enforcement system.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.474-478
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• 1986

The phenomenon of a continuous Steel-making process was studied with a set of collected equilibrium data for the steel-oxidation reactions. Mass and Heat balances were also established. Mass transfer constants which are physically unmeasurable but escential for the simulation study in the steel-making process were calculated from the experimental data using an optimization technique. Based on these data various operating conditions and process characteristics were examined.

• Journal of the Korea Computer Graphics Society
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• v.22 no.3
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• pp.53-61
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• 2016

In this paper, we propose an algorithm for generating lightning paths, which are more realistic than those of random tree based algorithm and faster than a physically based simulation algorithm. Our approach utilizes physically based Dielectric Breakdown Method (DBM) and approximates the electric potential field dramatically to generate the lightning path. We also show a guide path method for the lightning to avoid obstacles in a complex scene. Finally, our method renders fast and realistic lightning by considering physical characteristics for the thickness and brightness of the lightning stream. Our result of the lightning path shares similarity to natural phenomenon by having about 1.56 fractal dimensions, and we can generate the lightning path faster than a previous physically based algorithm. On the other hand, our method is difficult to apply on the real-time games yet, but our approach can be improved by performing the path generation algorithm with GPU in future.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.49-50
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• 2003

In this paper, we describe a precise relationship between measured mechanical properties of cloth and the particle model. T he proposed cloth model is compared with the tablecloth drape, furthermore it is validated by the visualization of cloth 3-D drapeability.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.907-909
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• 2004

에어포일(airfoil)이 공기속을 지날 때 양력이 발생한다. 공간상을 비행하는 물체에는 중력, 추력, 양력, 항력의 네 가지 힘이 작용한다. 본 논문에서는 항공역학의 연구결과를 바탕으로 차이니즈탑이란 물체가 회전하면서 수직상승과 호버링 그리고 하강하는 동안의 운동형태를 사실적이면서도 실시간으로 구현한다. 그 결과는 게임이나 비행 시뮬레이션에 응용할 수 있다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.911-914
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• 2005

Soft tissue characterization and modeling based on living tissues has been investigated in order to provide a more realistic behavior in a virtual reality based surgical simulation. In this paper, we characterize the nonlinear viscoelastic properties of intra-abdominal organs using the data from in vivo animal experiments and inverse FE parameter estimation algorithm. In the assumptions of quasi-linear-viscoelastic theory, we estimated the nonlinear material parameters to provide a physically based simulation of tissue deformations. To calibrate the parameters to the experimental results, we developed a three dimensional FE model to simulate the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively. The comparison between simulation and experimental behavior of pig intra abdominal soft tissue are presented to provide a validness of the tissue model using our approach.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.122-131
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• 1993

In this paper, we have developed a submicron Si MOSFET simulator, which is physically based on the hydrodynamic energy transport mode. The simulator was used to investigate the nonstationary transport effects and the transient phenomena in submicron Si MOSFET's. It is found that the velocity overshoot and the carrier heating are dominant transport mechanism near the drain end of the channel and the transient phenomena is more retained in a long channel MOSFET.