• Journal of the Korea Computer Graphics Society
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• v.12 no.3
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• pp.21-26
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• 2006

악성 종양은 현대인을 괴롭히는 대표적인 질병의 하나로 이를 치료하는데 흔히 이용되는 것이 방사선치료이다. 방사선 치료에서는 종양세포만을 찾아 방사선을 조사하는 것이 무엇보다 중요하다. 본 논문에서는 입자 시뮬레이터 Geant4와 볼륨렌더링을 이용하여 이러한 것을 가능하게 하는 방사선조사계획시스템을 제안하고 시스템의 논리적 구조와 구현 시 고려할 사항에 대하여 알아본다. 본 시스템은 Geant4에 있는 다양한 물리(physics)이론을 적용하여 방사선의 물성을 다양하고 정확하게 시뮬레이션 하고, 시뮬레이션으로 구한 방사선량 분포를 볼륨렌더링으로 생성한 영상과 함께 표시하여 사용자가 방사선 치료 계획을 용이하게 세울 수 있도록 한다.

• Journal of the Korea Computer Graphics Society
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• v.9 no.1
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• pp.1-2
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• 2003

본 논문에서는 액체와 기체가 상호작용 하는 현상들에 대한 새로운 유체 애니메이션 기법을 액체 속 공기방울의 예를 사용하여 제시한다. 기존의 자유표면 시뮬레이션 기법들과는 달리 액체와 기체를 함께 시뮬레이션 할 경우에는 기체의 유동과 액체의 유동을 동시에 다루어야 하며 비중 차에 의한 부력과 경계면에서의 표면장력 등을 추가적으로 고려해야 한다. 유체의 토폴로지 변화를 쉽게 다루면서도 수치적 분산을 막기 위하여 유체 역학 분야의 VOF (Volume of Fluid) 기법과 프론트 추적 (Front-tracking) 기법을 혼합하여 사용하였다. 액체와 기체의 경계면은 마칭 큐브즈 알고리즘을 사용하여 폴리곤으로 복원된 후 버텍스 쉐이더 기술들을 사용하여 액체-기체 경계면의 광학적인 특성을 표현할 수 있었다.

• Journal of the Korea Computer Graphics Society
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• v.17 no.4
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• pp.23-30
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• 2011

We propose an intelligent ribbon road network for automatic vehicle simulation, and a real-time algorithm for large-scale, realistic traffic simulation based on artificial energy functions. Our method reconstructs a road network automatically from both GIS (Geographic Information System) real-world data and synthetic models. Such automatic road network helps us to easily simulate almost every possible scenario such as intersections, ramps, etc. In order to simulate agents' movement, we design car-environment interaction energy and car-car interaction energy functions. Car agents move along the road network according to the proposed energy functions while avoiding collisions with other car agents.

• Journal of the Korea Computer Graphics Society
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• v.11 no.4
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• pp.39-44
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• 2005

인터랙티브 컴퓨터 게임과 컴퓨터 애니메이션에서, 유관절체의 움직임을 직관적으로 제어하도록 하는 것은 어려운 문제로 인식되고 있다. 이런 분야에서는 대부분 움직임의 대상이 되는 캐릭터가 많은 관절로 연결되어 있는데, 이때 각 관절을 사용자의 의도대로 쉽게 조종할 수 있도록 해주는 인터페이스를 디자인하기가 어렵기 때문이다. 본 논문에서는 자유도(DOF)가 높은 캐릭터의 움직임을 제어하기 위해 오랫동안 인형극에서 사용되고 있는 마리오넷 조종 기법[5]을 응용한 마리오넷 시스템을 제안하고자 한다. 우리는 가상 마리오넷 시스템을 물리기반 모델링과 햅틱 인터페이스를 기반으로 구현하였고, 이 시스템을 통해 높은 자유도를 가지는 유관절체 캐릭터의 복잡한 움직임을 쉽게 생성해낼 수 있었다. 그리고 사용자에게 햅틱 포스 피드백을 줌으로써 더욱 정교한 마리오넷을 조작이 가능하도록 하였다. 이 시스템을 일반적인 유관절체에 적용한다면 다양한 움직임을 쉽고 빠르게 생성할 수 있을 것이다.

• Journal of the Korea Computer Graphics Society
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• v.19 no.3
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• pp.1-11
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• 2013

Fluid Implicit Particle (FLIP) method is used in Visual Effect(VFX) industries frequently because FLIP based simulation show high performance with good visual quality. However in large-scale fluid simulations, the efficiency of FLIP method is low because it requires many particles to represent large volume of water. In this papers, we propose a novel hybrid method of simulating fluids to supplement this drawback. To improve the performance of the FLIP method by reducing the number of particles, particles are deployed inside thin layers of the inner surface of water volume only. The coupling between less-disspative solutions of FLIP method and viscosity solution of level set method is achieved by introducing a new surface reconstruction method motivated by surface reconstruction method[1] and moving least squares(MLS) method[2]. Our hybrid method can generate high quality of water simulations efficiently with various multiscale features.

• Journal of the Korea Computer Graphics Society
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• v.26 no.5
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• pp.15-24
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• 2020

We present a supervised learning method that estimates the simulation parameters required to simulate the fabric from the static drape shape of a given fabric sample. The static drape shape was inspired by Cusick's drape, which is used in the apparel industry to classify fabrics according to their mechanical properties. The input vector of the training model consists of the feature vector extracted from the static drape and the density value of a fabric specimen. The output vector consists of six simulation parameters that have a significant influence on deriving the corresponding drape result. To generate a plausible and unbiased training data set, we first collect simulation parameters for 400 knit fabrics and generate a Gaussian Mixed Model (GMM) generation model from them. Next, a large number of simulation parameters are randomly sampled from the GMM model, and cloth simulation is performed for each sampled simulation parameter to create a virtual static drape. The generated training data is fitted with a log-linear regression model. To evaluate our method, we check the accuracy of the training results with a test data set and compare the visual similarity of the simulated drapes.

• Journal of the Korea Computer Graphics Society
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• v.14 no.4
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• pp.27-33
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• 2008

Physics-based graphic techniques are used when simulating and rendering natural phenomena such as smoke, water and flame with computational physics. We propose novel methods which render simulated particle data fast onto 3D using tetrahedron splat. We calculate the position and the normal vector of splat by SPH(smoothed particle hydrodynamics) method then we reconstruct splat into quadrangular pyramid to reduce seam. We implement this technique for SPH fluid simulation, and animate natural flow of water successfully.

• Journal of the Korea Computer Graphics Society
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• v.22 no.1
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• pp.1-8
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• 2016

We propose a novel framework for controlling various and complex models using primitive model. To control original model, first we correspond original model to simplified primitive model that contains original model. After doing deformable simulation with primitive model, we compute original model by inversion of result. Since existing method can only control one type formed models, our method - which can control all difference formed models by only one primitive model - has contribution. In conclusion, we show results that efficiently and intuitionally control the various deformable models by using one example primitive model.

• Journal of the Korea Computer Graphics Society
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• v.3 no.1
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• pp.37-47
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• 1997

This paper presents the algorithms for generating ambient traffic in driving simulation. Each ambient car is modeled as an autonomous agent that obeys the traffic rules by sensing the traffic lights, road signs, lanes, and other cars around. The algorithm is localized to the area where the car driven by the participant is currently located. Therefore the complexity of the algorithm does not depend on the size of the road network, allowing a huge environment to be simulated with no extra overhead. To avoid monotony, we produce artificial fluctuations in the behavior by employing various forms of probability distribution functions. The resulting behavior of the ambient cars is quite realistic. Experiments indicate that it is hard to tell whether an ambient car is computer-controlled or human-controlled.

• The KIPS Transactions:PartA
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• v.14A no.7
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• pp.421-434
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• 2007

Among many other CG generated natural scenes, the representation of ocean surfaces is one of the most complicated and time-consuming problem because of its large extent and complex surface movement. We present a hybrid method to represent and animate unbound deep-water ocean surfaces by utilizing graphics processor as both simulation and rendering core. Our technique is mainly based on spectral approaches that generate a high-detailed height field using Fourier transform on a 2D regular grid. Additionally, we incorporate Gerstner model and generate low-detailed height field on a 2D projected grid in order to represent large waves and main structure of ocean surface. There is no interruption between CPU and GPU, and no need to transfer simulation results from the system memory to graphics hardware because the entire simulation and rending processes are done on graphics processor. As a result we can synthesize and render realistic water surfaces in real-time. Proposed techniques are readily adoptable to real-time applications such as computer games that have heavy work load on CPU but still demand plausible natural scenes.