• 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 the Korea Computer Graphics Society
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• v.18 no.1
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• pp.1-9
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• 2012

Video-based modeling / rendering developed to produce photo-realistic video contents have been one of the important research topics in computer graphics and computer visions. To smoothly combine original input video clips and 3D graphic models, geometrical information of light sources and cameras used to capture a scene in the real world is essentially required. In this paper, we present a simple technique to estimate the position and orientation of an optimal light source from the topology of objects and the silhouettes of shadows appeared in the original video clips. The technique supports functions to generate well matched shadows as well as to render the inserted models by applying the estimated light sources. Shadows are known as an important visual cue that empirically indicates the relative location of objects in the 3D space. Thus our method can enhance realism in the final composed videos through the proposed shadow generation and rendering algorithms in real-time.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.3
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• pp.275-287
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• 2000

A virtual reality system must provide participants with a natural interaction, a sufficient immersion, and mostly, realistic images. To achieve this, it is crucial to provide a fast and uniform rendering speed regardless of the complexity of virtual worlds, or the complexity of simulation. In this paper, a virtual reality system which offers an improved rendering performance for complex virtual reality applications has been designed and implemented. The key idea of the proposed system is to exploit the multi-thread scheme in system module design, and execute each modules in parallel. Taking such design approach, rendering, simulation, and interaction can be executed independently. Hence, in applications where a simulation is complex or a scene is very large, this system can provide a more uniform and faster frame rates. The proposed method has been experimented under the various application environments in which scenes and simulations are very complex.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.398-407
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• 2012

We propose a tree modeling method of expressing realistically and efficiently numerous trees distributed on a broad terrain. This method combines and simplifies the recursive hierarchy of tree branch and branch generation process through self-organizing from buds, allowing users to generate trees that can be used more intuitively and efficiently. With the generation process the leveled structure and the appearance such as branch length, distribution and direction can be controlled interactively by user. In addition, we introduce an environment-adaptive model that allows to grow a number of trees variously by controlling at the same time and we propose an efficient application method of growing environment. For the real-time rendering of the complex tree models distributed on a broad terrain, the rendering process, the LOD(level of detail) for the branch surfaces, and shader instancing are introduced through the GPU(Graphics Processing Unit). Whether the numerous trees are expressed realistically and efficiently on wide terrain by proposed models are confirmed through simulation.

• Proceedings of the Korea Contents Association Conference
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• 2006.05a
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• pp.259-264
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• 2006

Some appearances of the result images from the researches on NPR(Non Photorealistic Rendering) look like contrary to the attributes of the real painting. As they are based on only the technical approach rather than the aesthetic and accurate analysis of the real painting which they modeled. Therefore the purpose of this paper is the abstraction of the exact features from the related real painting, the redefine of them applicable to the process, and the embodiment of the painterly NPR algorithms. This paper modeled the Impressionism which were originated in the France at the late nineteenth century. Accordingly, at first, I analyzed the general features of oil paintings and Impressionism paintings, and according to this analyses, I adjusted them to engineering elements(the direction, length, width, texture and speed of stroke, the edge and region of object, depth information and color etc) and programmed. I emphasize the importance and potentiality of the collaboration of artist and technician in the NPR research through the results in this paper.

• Journal of Korea Game Society
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• v.13 no.3
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• pp.85-94
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• 2013

In this paper, we propose a scheme to reduce the number of shadow tests conducted during rendering of ray tracing. The shadow test is a very important process in ray tracing to generate photo-realistic images. In the rendering phase, the ray tracer determines whether to cull the shadow test based on information calculated from a shadow test conducted on the kd-tree in the preprocessing phase. In conventional rendering process, the proposed method can be used with little modification. The proposed method is suitable for a static scene, in which the geometry and light source does not change in the same manner as it does in the conventional method. The validity of the proposed scheme is verified and its performance is evaluated during cycle-accurate simulation. Through experiment results, we found that we could reduce up to 17% of the shadow test.

• The KIPS Transactions:PartB
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• v.14B no.4
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• pp.273-280
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• 2007

This paper presents a new 3D sound toolkit called $EVE-Sound^{TM}$ that consists of pre-processing tool for environment simplification preserving sound effect and 3D sound API for real-time rendering. It is designed so that it can allow users to interact with complex 3D virtual environments by audio-visual modalities. $EVE-Sound^{TM}$ toolkit would serve two different types of users: high-level programmers who need an easy-to-use sound API for developing realistic 3D audio-visually rendered applications, and the researchers in 3D sound field who need to experiment with or develop new algorithms while not wanting to re-write all the required code from scratch. An interactive virtual environment application is created with the sound engine constructed using $EVE-Sound^{TM}$ toolkit, and it shows the real-time audio-visual rendering performance and the applicability of proposed $EVE-Sound^{TM}$ for building interactive applications with complex 3D environments.

• Journal of KIISE
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• v.43 no.8
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• pp.835-840
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• 2016

Monte Carlo ray tracing has been widely used for simulating a diverse set of photo-realistic effects. However, this technique typically produces noise when insufficient numbers of samples are used. As the number of samples allocated per pixel is increased, the rendered images converge. However, this approach of generating sufficient numbers of samples, requires prohibitive rendering time. To solve this problem, image filtering can be applied to rendered images, by filtering the noisy image rendered using low sample counts and acquiring smoothed images, instead of naively generating additional rays. In this paper, we proposed a Stein's Unbiased Risk Estimator (SURE) based $\grave{A}$-Trous wavelet to filter the noise in rendered images in a near-interactive rate. Based on SURE, we can estimate filtering errors associated with $\grave{A}$-Trous wavelet, and identify wavelet coefficients reducing filtering errors. Our approach showed improvement, up to 6:1, over the original $\grave{A}$-Trous filter on various regions in the image, while maintaining a minor computational overhead. We have integrated our propsed filtering method with the recent interactive ray tracing system, Embree, and demonstrated its benefits.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.1-9
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• 2010

In this paper we present a shading technique for realistic rendering of the surfaces with irregular and complex textures using a single photograph. So far, most works have been using many photographs or special photographing equipment to render the surfaces with irregular and complex textures as well as dividing texture regions manually. We present an automatic selection method of the region segmentation techniques according to properties of materials. As our technique produces a reflectance model and the approximated Bidirectional Reflection Distribution Function(BRDF) parameters, it allows the recovery of the photometric properties of diffuse, specular, isotropic or anisotropic textured objects. Also it make it possible to present several synthetic images with novel lighting conditions and views.

• Journal of International Society for Simulation Surgery
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• v.3 no.2
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• pp.39-45
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• 2016

The augmented reality is the environment which consists of real-world view and information drawn by computer. Since the image which user can see through augmented reality device is a synthetic image composed by real-view and virtual image, it is important to make the virtual image generated by computer well harmonized with real-view image. In this paper, we present reviews of several works about computer vision and graphics methods which give user realistic augmented reality experience. To generate visually harmonized synthetic image which consists of a real and a virtual image, 3D geometry and environmental information such as lighting or material surface reflectivity should be known by the computer. There are lots of computer vision methods which aim to estimate those. We introduce some of the approaches related to acquiring geometric information, lighting environment and material surface properties using monocular or multi-view images. We expect that this paper gives reader's intuition of the computer vision methods for providing a realistic augmented reality experience.