• Journal of Digital Contents Society
• /
• v.9 no.2
• /
• pp.363-369
• /
• 2008

In this paper, we have proposed 3D shape reconstruction using superquadrics and single z-buffer Constructive Solid Geometry (CSG) rendering algorithm. Superquadrics can obtain various 3D model using 11 parameters and both superquadrics and deformed-superquadrics play a role of primitives which are consisted of CSG tree. In addition, we defined some effective equations using z-buffer algorithm and stencil buffer for synthesizing 3D model. Using this proposed algorithm, we need not to consider the coordinate of each 3D model because we simply compare the depth value of 3D model.

• Korean Journal of Computational Design and Engineering
• /
• v.15 no.2
• /
• pp.115-123
• /
• 2010

We present an efficient algorithm for computing the Hausdorff distance between two planar curves. The algorithm is based on an efficient trimming technique that eliminates the curve domains that make no contribution to the final Hausdorff distance. The input curves are first approximated with biarcs within a given error bound in a pre-processing step. Using the biarc approximation, the distance map of an input curve is then approximated and stored into the graphics hardware depth-buffer by rendering the distance maps (represented as circular cones) of the biarcs. We repeat the same procedure for the other input curve. By sampling points on each input curve and reading the distance from the other curve (stored in the hardware depth-buffer), we can easily estimate a lower bound of the Hausdorff distance. Based on the lower bound, the algorithm eliminates redundant curve segments where the exact Hausdorff distance can never be obtained. Finally, we employ a multivariate equation solver to compute the Hausdorff distance efficiently using the remaining curve segments only.

• Journal of the Korea Computer Graphics Society
• /
• v.9 no.4
• /
• pp.1-7
• /
• 2003

본 논문에서는 GPU와 스텐실 버퍼(stencil buffer) 및 깊이 버퍼(depth buffer)를 이용하여 가려진 픽셀들을 렌더링 단계 이전에 건너뛰는(skipping) 방법을 제시하고자 한다. 그래픽 카드에 기본적으로 제공되는 기능인 깊이 및 스텐실 버퍼 검사(depth & stencil buffer test)를 이용하여 이진 차폐 맵(binary occlusion map)을 만들고 이를 재사용하여 가려지는 부분의 픽셀들을 효과적으로 건너뛰게 하는 방법이다. 전체 볼륨 데이터는 팔진트리(octree) 구조를 가진 서브볼륨들로 나뉘어 저장되며 시점에 가까운 서브볼륨부터 렌더링에 사용된다. 서브볼륨들을 차례로 렌더링하면서 차폐 맵을 갱신하게 하면, 멀리 있는 서브볼륨들을 렌더링할 때 이미 가려진 픽셀들을 렌더링에서 제외할 수 있다.

• Journal of Korea Multimedia Society
• /
• v.9 no.1
• /
• pp.41-50
• /
• 2006

This paper aims to improve the efficiency of a 3D-graphic software engine in a PDA platform and the performance of a rasterizer. There are many problems in implementing a software engine in a mobile platform, due to its relatively weak processing power. Taking the advantages and complementing weaknesses of the depth-sort algorithm and the Z-buffer algorithm, we implemented an adaptive Z-buffer algorithm and proved its performance on several PDA platforms. Our algorithm was evaluated to have midway speed compared with two conventional algorithms. It also removed reversal errors in comparison with the depth-sort algorithm.

• Journal of KIISE:Computer Systems and Theory
• /
• v.27 no.1
• /
• pp.13-22
• /
• 2000

We present a method that enhances the rendering speed of z-buffer algorithm using temporal coherence between two contiguous frames on fixed viewing conditions. Conventional z-buffer algorithm stores depth value for each pixel on a view plane while rendering some polygons, then it determines the visibility of the remaining polygons based on the stored depth values. If we can get color and depth information for some polygons without rendering, it is possible to generate an image by rendering only the remaining ones. In case of high frame rate, we can find the fact that sets of static polygons of the two contiguous frames are almost the same. This temporal coherence enables us to get the color and depth information of static polygons efficiently. Our algorithm stores color and depth information of static polygons and reuses it for generating the next frame. This method can be easily implemented since it does not require complex data structure and modification for conventional z-buffer algorithm. Also it is adequate for hardware implementation.

• Journal of Electrical Engineering and information Science
• /
• v.3 no.2
• /
• pp.202-210
• /
• 1998

This paper is concerned with an efficient generation of stereoscopic views for complex virtual environments by exploiting frame coherence in visibility. The basic idea is to keep visible polygons throughout the rendering process. P-buffer, a buffer of image size, holds the id of the visible polygon for each pixel. This contrasts to the frame buffer and the Z-buffer which hold the color information and the depth information, respectively. For the generation of a consecutive image, the position and the orientation of the visible polygons in the current view are updated according to the viewer's movements, and re-rendered on the current image under the assumption that, when the viewer moves slightly, the visibility of polygons remains unchanged. In the case of stereoscopic views, it may not introduce much difficulty when we render the right(left) image using visible polygons on the (right) image only, The less difference in two images is, the easier the matching becomes in perceiving depth. Some psychophysical experiments have been conducted to support this claim. The computational complexity for generating a fight(left) image from the previous left(right) image is bounded by the size of image space, and accordingly. It is somewhat independent of the complexity of the 3-D scene.

• Journal of the Korea Computer Graphics Society
• /
• v.20 no.2
• /
• pp.13-24
• /
• 2014

In this study, a graphics-processing-unit (GPU)-based acceleration technique is proposed for the feature-based image morphing. This technique uses the depth-buffer of the graphics hardware to calculate efficiently the shortest distance between a pixel and the control lines. The pairs of control lines between the source image and the destination image are determined by user's input, and the distance function of each control line is rendered using two rectangles and two cones. The distance between each pixel and its nearest control line is stored in the depth buffer through the graphics pipeline, and this is used to conduct the morphing operation efficiently. The pixel-unit morphing operation is parallelized using the compute unified device architecture (CUDA) to reduce the morphing time. We demonstrate the efficiency of the proposed technique using several experimental results.

• International Journal of CAD/CAM
• /
• v.4 no.1
• /
• pp.47-53
• /
• 2004

The subdivision surface is the limit of recursively refined polyhedral mesh. It is quite intuitive that the multi-resolution feature can be utilized to simplify generation of NC (Numerical Control) tool paths for rough machining. In this paper, a new method of parallel NC tool path generation for subdivision surfaces is presented. The basic idea of the method includes two steps: first, extending G-Buffer to a strip buffer (called S-Buffer) by dividing the working area into strips to generate NC tool paths for objects of large size; second, generating NC tool paths by parallel implementation of S-Buffer based on MPI (Message Passing Interface). Moreover, the recursion depth of the surface can be estimated for a user-specified error tolerance, so we substitute the polyhedral mesh for the limit surface during rough machining. Furthermore, we exploit the locality of S-Buffer and develop a dynamic division and load-balanced strategy to effectively parallelize S-Buffer.

• Textile Coloration and Finishing
• /
• v.4 no.2
• /
• pp.76-83
• /
• 1992

Wool tropical and nylon taffeta were treated with low temperature plasma of $O_2$, $N_2$, NH$_3$, CF$_4$ and CH$_4$ for the intervals of 10 to 300 sec, and then dyed with leveling and milling type acid dyes in presence or absence of buffer solution. From the color depth of dyed fabrics, effect of plasma gases, treated time, dyeing time and temperature on dyeing property was studied. The results of the experiment can be summarized as follows: 1) The plasma treatments except methane gas increased the color depth of dyed wool fabrics, but not that of dyed nylon fabrics regardless of the plasma gases used. 2) The color depth of wool fabrics dyed in the dye bath without buffer solution was increased by the low temperature plasma, especially increased much more by CF$_4$ plasma treatment. It is found that with the identification of F- ion in the residual dye bath the hydrogen fluoride gas was adsorbed on wool fabrics in the plasma treatment. 3) The color depth of wool fabrics was increased with the time of $O_2$ and CF$_4$ plasma treatments. 4) In both cases of the leveling and milling type acid dyes, the rate of dyeing was increased in the low temperature plasma treatments, and it is found that the leveling type acid dye increased the color depth at relatively low temperature below 4$0^{\circ}C$, compared with the milling type acid dye.

• Nuclear Engineering and Technology
• /
• v.44 no.1
• /
• pp.89-102
• /
• 2012

The buffer and backfill are important components of the engineered barrier system in a high-level waste repository, which should be constructed in a hard rock formation at a depth of several hundred meters below the ground surface. The primary function of the buffer and backfill is to seal the underground excavation as a preferred flow path for radionuclide migration from the deposited high-level waste. This study investigates the hydraulic conductivity and swelling pressure of Kyungju Ca-bentonite, which is the candidate material for the buffer and backfill in the Korean reference high-level waste disposal system. The factors that influence the hydraulic conductivity and swelling pressure of the buffer and backfill are analyzed. The factors considered are the dry density, the temperature, the sand content, the salinity and the organic carbon content. The possibility of deterioration in the sealing performance of the buffer and backfill is also assessed.