• The KIPS Transactions:PartB
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• v.14B no.6
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• pp.413-422
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• 2007

This paper addresses a new technique for constructing surface model from a set of wire-frame contours. The most difficult problem of this technique, called contour triangulation, arises when there are many branches on the surface, and causes lots of ambiguities in surface definition process. In this paper, the branching problem is reduced as the surface reconstruction from a set of virtual belts and virtual canyons. To tile the virtual belts, a divide-and-conquer strategy based tiling technique, called the BPA algorithm, is adopted. The virtual canyons are covered naturally by an iterative convex removal algorithm with addition of a center vertex for each branching surface. Compared with most of the previous works reducing the multiple branching problem into a set of tiling problems between contours, our method can handle the problem more easily by transforming it into more simple topology, the virtual belt and the virtual canyon. Furthermore, the proposed method does not involve any set of complicated criteria, and provides a simple and robust algorithm for surface triangulation. The result shows that our method works well even though there are many complicated branches in the object.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.58-58
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• 2010

Reactive or unstable adsorbates are often difficult to study spectroscopically. They may have, for instance, resonance states lying close to the Fermi level, inducing them to desorb or decompose by the probe itself, low-energy tunneling electrons. In order to overcome this limitation, we developed a novel method, which we call x-ramp scan. The method sweeps the bias voltage, with the simutaneous scan along the imaging direction, in a constant current mode. This mapping yields the tip-height variation as a function of bias, or Z(V), at nominally always fresh surface. We applied this method to the investigation of methanol-induced molecular features, attributed to methoxy, found on NiAl(110) surface. These were produced by methanol molecules deposited by a pulse injection method onto the metallic surface. Our study shows adsorbed methoxy are very reactive to the bias voltage, rendering the standard spectroscopy useless. Our new x-ramp scan shows that the decomposition of adsorbates occurs at the sample bias of 3.63 V, and proceeds with the lifetime of a few milliseconds. The details of the method will be provided at the discussion.

• Journal of Korean Society for Geospatial Information Science
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• v.6 no.2 s.12
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• pp.133-141
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• 1998

Terrain modelling is composed of a method using the rectangular grid and another using the triangulated irregular network. The method using the triangulated irregular network is most widely used because it can express the characteristics of the terrain well with only a small amount of information on the terrain and also reduces the rendering time. The process of extracting the surface-specific point and a triangular process is needed to construct such triangulated irregular network. This paper concentrates on the process of extracting the surface-specific point. The 8-direction neighborhood method and other transformed methods of the former method are frequently used to extract the surface-specific point. Another method which eliminates the unnecessary points using the Polygon reduction method is also suggested However, the 8-direction neighborhood method has a big fault of also drawing out some unnecessary points. To resolve such problem, we suggest a method of extracting the surface-specific point using the cross section of the terrain. This method reduces the time to extract the surface-specific point and enables a more precise extraction with less terrain information.

• Journal of Broadcast Engineering
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• v.25 no.5
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• pp.655-664
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• 2020

Free viewpoint image synthesis technology is one of the important technologies in the MPEG-I (Immersive) standard. RVS (Reference View Synthesizer) developed by MPEG-I and in use in MPEG group is a DIBR (Depth Information-Based Rendering) program that generates an image at a virtual (intermediate) viewpoint from multiple viewpoints' inputs. RVS uses the mesh surface method based on computer graphics, and outperforms the pixel-based ones by 2.5dB or more compared to the previous pixel method. Even though its OpenGL version provides 10 times speed up over the non OpenGL based one, it still shows a non-real-time processing speed, i.e., 0.75 fps on the two 2k resolution input images. In this paper, we analyze the internal of RVS implementation and modify its structure, achieving 34 times speed up, therefore, real-time performance (22-26 fps), through the 3 key improvements: 1) the reuse of OpenGL buffers and texture objects 2) the parallelization of file I/O and OpenGL execution 3) the parallelization of GPU shader program and buffer transfer.

• Progress in Medical Physics
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• v.16 no.1
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• pp.47-51
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• 2005

We report a case of an accidental extravasation of contrast material. A large-volume extravasation occurred in an adult during spiral contrast-enhanced CT. The amount of contrast material extravasated was 47 ml. The patient had a swelling of the dorsum right hand. The extravasation injury site was determined by CT scanning. The extavasation case was examined using five separate display techniques: axial, multi planar reformation (MPR), maximum intensity projection (MIP), volume rendering, and shaded-surfaced display (SSD). This paper introduces extravasation with the CT and the three-dimensional appearance.

• Journal of Korea Game Society
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• v.9 no.3
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• pp.97-105
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• 2009

In this paper, we propose a new rendering scheme of cloth by measuring light-scattering pattern inside the cloth and reproducing using the pattern. To date, the BTF(Bidirectional Texture Function) has been one of the most appropriate method to realistically reconstruct cloth surface. However, the BTF has a couple of defects that it ultimately requires an infinite amount of data and all light effects should be used all together. We noted that internal scattering has a decisive contribution to the reality of cloth. Following this observation, we take an image of a ray of light scattering inside cloth for every position of the cloth sample and determine each pixel value by adding up all light influences arriving from its vicinity. Our method we propose in this paper provides a clue to more realistically represent cloth-like materials, which is one of the most challenging materials to express, by enabling each ray to be controlled individually.

• Journal of the Korea Computer Graphics Society
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• v.16 no.3
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• pp.41-48
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• 2010

Photon mapping is a traditional global illumination method using many photons emitted from the light source for photo-realistic rendering. However, this method needs a lot of resources to perform tracing of millions of photons. Progressive photon mapping solves this problem. Typical progressive photon mapping performs ray tracing at first to find the hit points on diffuse surface of objects. Next, light source repeatedly emits a small number of photons in photon tracing pass, and power of photons in each sphere that has a fixed radius with the hit points in the center is accumulated. This method requires less resources than previous photon mapping, but it spends much time for gathering enough photons since each of photons progresses through a random direction and rendering high quality image. To improve the method, we propose photon probing that calculates variance of photons in the sphere and controls radius of sphere. In addition, we apply cone filter in radiance estimation step for reducing aliasing at the edges in result image.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.189-198
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• 1998

3D medical image reconstruction techniques are useful to figure out complex 3D structures from the set of 2D sections. In the paper, 3D medical image reconstruction system is constructed under PC environment and programmed based on modular programming by using Visual C++ 4.2. The whole procedures are composed of data preparation, gradient estimation, classification, shading, transformation and ray-casting & compositing. Three speed optimization techniques are used for accelerating 3D medical image reconstruction technique. One is to reduce the rays when cast rays to reconstruct 3D medical image, another is to reduce the voxels to be calculated and the other is to apply early ray termination. To implement 3D medical image reconstruction system based on PC, speed optimization techniques are experimented and applied.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.123-133
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• 2011

In this paper, we propose a new method for toon shading using 3D texture which renders 3d objects in a cartoon style. The conventional toon shading using 1D texture displays shading tone by computing the relative position and orientation between a light vector and surface normal. The 1D texture alone has limits to express the various tone change according to any viewing condition. Therefore Barla et. al. replaces a 1D texture with a 2D texture whose the second dimension corresponds to the view-dependent effects such as level-of-abstraction, depthof-field. The proposed scheme extends 2D texture to 3D texture by adding one dimension with the geometric information of 3D objects such as curvature, saliency, and coordinates. This approach supports two kinds of extensions for cartoon style diversification. First, we support "shape exaggeration effect" to emphasize silhouette or highlight according to the geometric information of 3D objects. Second, we further incorporate "cartoon specific effect", which is examples of screen tone and out focusing frequently appeared in cartoons. We demonstrate the effectiveness of our approach through examples that include a number of 3d objects rendered in various cartoon style.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.1120-1125
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• 2006

자연 현상에서 나타나는 물이나 바다와 같은 유체를 3 차원으로 시뮬레이션하는데 있어서 가장 중요한 요소는 실시간에 사실적으로 실행 가능하도록하는 것이다. 유체 모델은 특정 상황에 따른 다양한 방정식과 많은 파라미터값에 의해 제어되기 때문에 시뮬레이션하는데 많은 어려움이 따른다. 또한 복잡한 물리 수식을 기반으로 하기 때문에 유체 모델을 시뮬레이션하기 위해서는 많은 수행 시간이 소요된다. 본 논문에서는 실시간 유체와 강체(rigid body) 사이의 상호작용을 표현하기 위해 간략화된 유체 표면 모델(Fluid-Surface Model)을 제안하고, 개선된 계산과정을 통해 보다 빠르게 시뮬레이션하도록 한다. 또한 본 논문에서는 유체의 표면과 강체의 상호작용을 표현하는데 있어서 유체의 항력에 의해서 강체와 충돌시 발생하는 유체 표면의 움직임을 강체 모델의 제어를 통해 나타낸다. 본 논문에서 제안하는 자연스러운 유체 표면 모델은 유체역학적 방법을 사용하여 실시간에 사실적으로 표현된다. 그리고 이러한 유체 표면 모델을 PC 환경에서 사용자와 상호작용 가능하도록 재현하여, 게임이나 애니메이션에서의 유체 모델들에도 적용할 수 있다.