• Journal of Broadcast Engineering
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• v.26 no.6
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• pp.680-691
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• 2021

Due to the recent developments of attaining 3D contents by using devices such as 3D scanners, the diversity of the contents being used in AR(Augmented Reality)/VR(Virutal Reality) fields is significantly increasing. There are several ways to represent 3D data, and using point clouds is one of them. A point cloud is a cluster of points, having the advantage of being able to attain actual 3D data with high precision. However, in order to express 3D contents, much more data is required compared to that of 2D images. The size of data needed to represent dynamic 3D point cloud objects that consists of multiple frames is especially big, and that is why an efficient compression technology for this kind of data must be developed. In this paper, a motion estimation and compensation method for dynamic point cloud objects using 3D DCT is proposed. This will lead to switching the 3D video frames into I frames and P frames, which ensures higher compression ratio. Then, we confirm the compression efficiency of the proposed technology by comparing it with the anchor technology, an Intra-frame based compression method, and 2D-DCT based V-PCC.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.366-370
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• 2010

This paper presents an automatic Oriental ink-rendering technique that recreates the artistic style of Oriental paintings from a single image. In Oriental paintings are characterized by strokes with various thickness and disordered dispersion. In this study, a stroke drawing method was developed based on the canny edge detector and radial curvature that are suitable for lines with varied thickness even along a single stroke. A dispersion-shading method was likewise developed by applying a set of iterated dual-filtering, and intensity exaggeration methods. The dispersion-shading method is designed to increase the local shade details, to decrease the global shade. Unlike the existing watercolor-rendering and abstraction system the proposed dispersion-shading method achieves disordered shade details rather than simplification.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.1
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• pp.33-42
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• 2001

Recently, the interests in the 3D image, generated from the range data and CAD, have exceedingly increased, accordingly a various 3D image database is being constructed. The efficient and fast scheme to access the desired image data is the important issue in the application area of the Internet and digital library. However, it is difficult to manage the 3D image database because of its huge size. Therefore, a proper descriptor is necessary to manage the data efficiently, including the content-based search. In this paper, the proposed shape descriptor is based on the voxelization of the 3D image. The medial axis transform, stemming from the mathematical morphology, is performed on the voxelized 3D image and the graph, which is composed of node and edge, is generated from skeletons. The generated graph is adequate to the novel shape descriptor due to no loss of geometric information and the similarity of the insight of the human. Therefore the proposed shape descriptor would be useful for the recognition of 3D object, compression, and content-based search.

• Journal of the Korea Computer Graphics Society
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• v.20 no.2
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• pp.1-11
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• 2014

The quality of 2D-to-3D conversion depends on the accuracy of the assigned depth to scene objects. Manual depth painting for given objects is labor intensive as each frame is painted. Specifically, a human is one of the most challenging objects for a high-quality conversion, as a human body is an articulated figure and has many degrees of freedom (DOF). In addition, various styles of clothes, accessories, and hair create a very complex silhouette around the 2D human object. We propose an efficient method to estimate visually pleasing depths of a human at every frame in a monocular video. First, a 3D template model is matched to a person in a monocular video with a small number of specified user correspondences. Our pose estimation with sequential joint angular constraints reproduces a various range of human motions (i.e., spine bending) by allowing the utilization of a fully skinned 3D model with a large number of joints and DOFs. The initial depth of the 2D object in the video is assigned from the matched results, and then propagated toward areas where the depth is missing to produce a complete depth map. For the effective handling of the complex silhouettes and appearances, we introduce a partial depth propagation method based on color segmentation to ensure the detail of the results. We compared the result and depth maps painted by experienced artists. The comparison shows that our method produces viable depth maps of humans in monocular videos efficiently.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10b
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• pp.487-489
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• 2000

3차원 모델을 바탕으로 실루엣 에지를 찾아 디스플레이 해주는 대부분의 시스템들은 삼각 메쉬를 기반으로 한 모델 표현법을 사용하고 있다. NPR(nonphotorealistic rendering)에서 가장 초점을 두는 것은 컴퓨터로 렌더링된 결과가 사람이 그린듯한 효과를 줄 수 있느냐에 있다. 기존에 연구된 대부분의 시스템들은 사람이 그린듯한 효과를 주기 위해 물체의 표면에 대한 텍스츄어(Texture)와 어두운 정도, 그리고 스트록(Stroke)을 표면의 윤곽에 맞도록 그리는 많은 기법들을 소개해 왔다. 본 논문에서는 NPR 표현의 가장 기본이 되는 실루엣 에지 추출에 초점을 두고 추출한 실루엣 에지에 대해 파라미터화된 브러쉬 함수(Parameterized Brush Functions)를 적용하여 다양한 스타일로 디스플레이할 수 있는 기법을 제시한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.451-454
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• 2002

충돌검사는 사실감 있는 3 차원 공간을 시뮬레이션 하기 위해서 필수적인 요소이다. 본 논문에서는 BSP 로 표현될 수 있는 정적 게임환경과 Bounding Sphere 로 표현될 수 있는 움직이는 물체와의 효과적인 충돌검사 방법에 대해서 기술하고 있다. 본 논문에서 제안하는 충돌검사 알고리즘은 단 하나의 BSP 트리를 사용하여 임의의 크기의 bounding sphere 와 충돌검사를 할 수 있다는 장점을 가진다.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.1262-1270
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• 2006

사실적인 물 애니메이션을 위한 격자 기반 시뮬레이션 기법은 자연스러운 물의 움직임뿐만 아니라 부드러운 물의 표면을 잘 표현해주는 장점이 있다. 이러한 격자 기반 방법과 함께 상대적으로 적은 계산으로 안정적인 결과를 산출해주는 입자 기반의 액체 시뮬레이션 기법이 최근 애니메이션 분야에 적용되기 시작했고, 그로 인하여 입자로 이루어진 시뮬레이션 데이터에 특화된 효과적인 렌더링 기술의 개발이 요구되고 있다. 본 논문에서는 주로 3차원 스캔 데이터와 같이 물체 표면을 샘플링 하여 얻어진 점 집합에 대한 렌더링 기법을 확장하여, 위상 변화가 크고 점 집합에 의해 내부까지 표현되는 물 데이터의 특성에 적합한 렌더링 기법을 제안한다. 본 기법에서는 시뮬레이션을 통하여 얻은 입자 데이터로부터 물의 표면을 표현해주는 새로운 점 집합을 생성하고, 시뮬레이션 된 데이터의 특성을 잘 반영하도록 각 점에 대한 법선 벡터와 반지름을 결정한다. 특히 가공된 점 집합 데이터에 대하여 확장된 점 집합 렌더링 기법을 적용함으로써 입자 데이터가 표현해주는 세밀한 부분들을 보존하면서, 부드러운 물의 표면을 가시화할 수 있도록 하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.5_6
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• pp.297-304
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• 2004

In this paper, a mesh simplification algorithm based on wavelet transform and 2D planar sampling is proposed for efficient handling of 3D objects in computer applications. Since 3D vertices are directly transformed with wavelets in conventional mesh compression and simplification algorithms, it is difficult to solve tiling optimization problems which reconnect vertices into faces in the synthesis stage highly demanding vertex connectivities. However, a 3D mesh is sampled onto 2D planes and 2D polygons on the planes are independently simplified in the proposed algorithm. Accordingly, the transform of 2D polygons is very tractable and their connection information Is replaced with a sequence of vertices. The vertex sequence of the 2D polygons on each plane is analyzed with wavelets and the transformed data are simplified by removing small wavelet coefficients which are not dominant in the subjective quality of its shape. Therefore, the proposed algorithm is able to change the mesh level-of-detail simply by controlling the distance of 2D sampling planes and the selective removal of wavelet coefficients. Experimental results show that the proposed algorithm is a simple and efficient simplification technique with less external distortion.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.12
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• pp.641-655
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• 2007

Parameterization has been one of very important research subjects in several application areas including computer graphics. In the parameterization research, the problem of mapping 3D polygonal model to 2D plane has been studied frequently, but the previous methods often fail to handle complicated shapes of polygonal surfaces effectively as well as entail distortion between the 3D and 2D spaces. Several attempts have been made especially to reduce such distortion, but they often suffer from the problem when an arbitrary rectangular surface region on 3D model is locally parameterized. In this paper, we propose a new local parameterization scheme based on the projection level set method. This technique generates a series of equi-distanced curves on the surface region of interest, which are then used to generate effective local parameterization information. In this paper, we explain the new technique in detail and show its effectiveness by demonstrating experimental results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.476-477
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• 2022

This study deals with rotation, which is one of the expression methods of motion used in the 3D development environment. Euler angle is a rotation method introduced by Leonhard Euler to display objects in three-dimensional space. Although three angles can handle all rotations in a three dimensional coordinate space, there are serious errors in this approach. If you rotate an object with Euler angles, you will face the problem of gimbal locks that cannot rotate under certain circumstances. In contrast to this, the method to rotate an object without a gimbal lock is the quaternion rotation with quaternion. Rather than a detailed mathematical proof of quaternion, it introduces what concept is used in the current 3D development environment, and applies it to camera rotation control to implement a rotating camera without a gimbal lock.