격자간 거리 및 방향 정보를 활용한 흡입구 RCS 해석에 적합한 Ray-Tracing 가속화 방법

장인모,이동호,이일우 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

전투기 형상의 전방 RCS 에서 큰 비중을 차지하는 Inlet Cavity 에 의한 영향성은 SBR(Shooting and Bouncing Rays)기법을 통해 예측이 가능하지만, 이 기법은 Ray Tracing 과정에서 소요 계산시간이 많다는 문제점이 있다. 따라서 본 연구에서는 Fewer Ray-Object Intersections 의 일환으로 격자간의 상대적인 방향 및 거리정보를 통해 Ray 의 진행방향과 근접한 방향의 격자를 우선적으로 선별하고, 선별된 그룹을 가까운 것부터 Test 하는 방식으로 Ray-Tracing 과정을 가속화하였다. Ray 의 진행방향 기준으로 격자의 우선선별 정도에 따라 계산시간과 신뢰도가 서로 반비례적인 특성이 있긴 하지만, 단순한 형상의 경우 제안방법은 신뢰도를 99.9% 이상을 유지하면서 기존방법대비 절반가량 계산시간을 단축할 수 있었음을 시뮬레이션을 통해 확인했다. SBR(Shooting and Bouncing Rays) enables us to predict RCS contribution by inlet cavities of aircraft which is great part of the front RCS of the aircraft. However, ray tracing process in SBR requires considerable computation times: slow performance. In this paper, a new method to accelerate ray tracing process is proposed in which the main idea is to give facets priorities to be tested based on their directions and distances from ray"s incident angle and starting-point. Even though the amount of facets given priorities may change reliability and computation times of this method, the proposed method is able to cut in half computation times with 99.9% of reliability in case of simple cavity simulation.

헤드 마운티드 디스플레이를 위한 시간 제약 렌더링을 이용한 적응적 포비티드 광선 추적법

김영욱,임인성 (사)한국컴퓨터그래픽스학회 2022 컴퓨터그래픽스학회논문지 Vol.28 No.3

Ray tracing-based rendering creates by far more realistic images than the traditional rasterization-based rendering. Howeve r, it is still burdensome when implemented for a Head-Mounted Display (HMD) system that demands a wide field of view and a high display refresh rate. Furthermore, for presenting high-quality images on the HMD screen, a sufficient number of ray sampling should be carried out per pixel to alleviate visually annoying spatial and temporal aliases. In this paper, we e xtend the recent selective foveated ray tracing technique by Kim et al. [1], and propose an improved real-time rendering tec hnique that realizes the rendering effect of the classic Whitted-style ray tracing on the HMD system. In particular, by comb ining the ray tracing hardware-based acceleration technique and time-constrained rendering scheme, we show that fast HMD ray tracing is possible that is well suited to human visual systems. 광선 추적 기반의 렌더링은 래스터화 기반의 렌더링보다 훨씬 더 사실적인 이미지를 생성한다. 하지만 넓은시야와 높은 디스플레이 갱신 속도를 요구하는 헤드 마운티드 디스플레이(HMD) 시스템을 대상으로 이를 구현할 때에는 여전히 많은 연산량으로 인하여 부담스럽다. 또한, HMD 화면에 고품질 이미지를 표시하기 위해서는시각적으로 성가신 공간적/시간적 앨리어스를 줄이기 위해 픽셀당 충분한 수의 광선 샘플링을 수행해야 한다. 본 논문에서는 최근 Kim 등[1]이 제시한 선택적 포비티드 광선 추적법을 확장하여 주어진 HMD 시스템에서 고전적인 Whitted-스타일 광선 추적 수준의 렌더링 효과를 효율적으로 생성해주는 실시간 렌더링 기법을 제안한다. 특히, GPU의 광선 추적 하드웨어를 통한 가속과 시간 제한을 둔 렌더링 방법의 결합을 통하여 고속의HMD 광선 추적에 적합한 사람의 시각 시스템에 매우 효율적인 적응적 광선 샘플링 방법을 제안한다.

광선추적과 스펙트럼에 대한 교사와 중학생의 개념 유형 분석

이재봉,남경운,손정우,이성묵 한국과학교육학회 2004 한국과학교육학회지 Vol.24 No.6

본 연구의 목적은 중학교 교사와 학생들을 대상으로 광선추적과 스펙트럼에 대한 교사와 학생의 개념 유형을 비교하는 것이다. 본 연구에서는 7학년 '빛 단원에서 가장 중요하다고 생각되는 핵심개념은 광선추적과 스펙트럼에 의해 파악할 수 있다고 전제하고, 이에 대한 교사와 학생의 개념 유형을 조사하였다. 연구 대상은 서울ㆍ경기지역 과학교사 10명과 이들에게 배운 학생 328명이다. 모든 검사문항은 광선추적법과 스펙트럼 방법을 적용하는 문항으로 구성하였다. 연구결과 광선추적과 스펙트럼에 대한 교사와 학생들의 개념유형에는 차이가 있었다. 또한 대부분의 교사와 학생들은 상이 생기는 근본원리에 대하여 정확하게 알지 못하였다. 광선추적법을 알지 못하여 반사와 굴절에 의한 상을 찾을 때, 물체에서 나온 두 개 이상의 광선을 그려서 상을 찾는 경우는 거의 없었고, 하나의 광선으로 임의의 위치에서 상을 찾거나 평소 암기하고 있던 상의 위치를 표시하였다. 그리고 색에 대하여는 교사와 학생들은 개념을 이해하지 못하고, 교사들은 학생들에게 원리에 대한 설명 없이 현상을 제시하였다. 즉 교사와 학생들은 색에 대해서 단순 암기하고 있었다. The purpose of this study is to understand the types of teacher and student's concept on ray-tracing and spectrum in middle school. This study suggest key-concepts that is most important to "Light" unit in the seven grades : the ray-tracing and the spectrum. We examined the types of teacher and student's concept. We selected 10 teacher and 328 students who had learned by 10 teachers in Seoul and Gyeonggi. The problems were composed with the question item regarding all ray-tracing or the spectrum. From the analysis, it was found that the types of teacher and student's concept on ray-tracing and spectrum is different. The most of teacher and student didn't understand the basic principle of image formation. In case of context about formation of image by reflection and refraction, because they don't know ray-tracing, they do not try to find the position of the image by drawing two rays. Most of them used one ray comes from the one position of the object and indicated the position of image by memorized position. Also almost there was not a case which uses a ray tracing accurately. In the case of understanding color, they didn't understand the concept of color(or spectrum) and teachers represented to students the color phenomena without explanation of principles. In the result teachers and students would learn color science by rote.

광선 그룹화를 이용한 SBR 가속기법

이재인,윤달재,양성준,양우용,배준우,김시호,명로훈 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.6

The SBR technique is one of the asymptotic high frequency method, where a dense grid of rays are launched and traced to analyze the scattering properties of the target. In this paper, we propose an accelerated SBR technique using grouping a central ray and 8 surrounding rays around the center ray. First, launched rays are grouped into groups consisting of a central ray and 8 surrounding rays. After the central ray of each group is preferentially traced, 8 surrounding rays are rapidly traced using the information of ray tracing for the central ray. Simulation result of scattering analysis for CAD models verifies that the proposed method reduces the computational time without decreasing the accuracy.

Research on Parallel KD-Tree Construction for Ray Tracing

Zhang Peicheng,Xu Huahu,Bian Minjie,Honghao 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.11

Many computer graphics rendering algorithms and techniques use ray tracing for generation of photo-realistic images, and kd-tree is the most popular acceleration data structure for ray tracing. In order to avoid the inefficient parallel performance of kd-tree construction based on surface area heuristic (SAH), an algorithm using Morton code and path compression was present in this paper. Instead of building a kd-tree layer-by-layer, the proposed approach can be performed in parallel from bottom of a conceptual perfect binary tree. Experimental results on GPU show that our work achieves a faster kd-tree construction procedure.

Ray-tracing 기법을 이용한 축변위 그레고리안 안테나 설계

김춘원(Chun-Won Kim) 한국항공우주학회 2014 韓國航空宇宙學會誌 Vol.42 No.6

본 논문에서는 Ray-tracing 기법을 이용하여 그레고리안 안테나의 부반사판을 축변환 후 회전하여 급전혼으로 회귀되는 전파를 없애 이득 및 정재파비를 개선 시키고 부반사판의 크기와 전체적인 부피를 줄여 효율적인 구조를 갖는 축변위그레고리안 안테나를 설계하였다. 설계된 급전혼의 방사패턴을 이용하여 급전혼-부반사판-주반사판으로 전달되는 전파의 경로를 추적하여 주반사판 개구면에서의 전계분포를 구하고 이로부터 원거리 복사패턴을 계산하는 프로그램을 작성하여 안테나 성능을 최적화 하였다. 설계된 안테나는 CST와 제작·측정을 통해 계산결과와 비교하여 이득, 빔폭, 방사패턴, 부엽준위, 반사손실이 계산 결과와 매우 유사함을 확인함으로써 Ray-tracing기법에 대한 타당성을 검증하였다. In this paper, we designed axis-displaced Gregorian antenna by using Ray-tracing method. This antenna improves gain , VSWR by rotating the axis of the sub-reflector to get rid of E-field wave returned from sub-reflector to feed horn. Therefore it reduce the sub-reflector size and the volume of antenna. This method is used to track the propagation path for radiation pattern of feed horn from feed horn to sub-reflector, main-reflector and air. We get E-field distribution of this antenna aperture and calculate antenna radiation pattern and optimize the antenna performance. The Ray-tracing Method was verified because the gain, radiation patterns, side lobe level, beam width and return loss of the designed antenna are very similar to CST simulation result and a measured result of the fabricated antenna.

Construction of efficient kd-trees for static scenes using voxel-visibility heuristic

Choi, B.,Chang, B.,Ihm, I. Pergamon Press ; Elsevier Science Ltd 2012 Computers & graphics Vol.36 No.1

In the ray-tracing community, the surface-area heuristic (SAH) is used as a de facto standard strategy for building high-quality kd-trees. Although widely accepted as the best kd-tree construction method, it is based only on the surface-area measure, which often fails to reflect effectively the rendering characteristics of a given scene. This paper presents new cost metrics that help produce improved kd-trees for static scenes by considering the visibility of geometric objects, which can affect significantly the actual distribution of rays during ray tracing. Instead of the SAH, we apply a different heuristic based on the new concept of voxel visibility, which allows more sophisticated estimation of the chance of a voxel being hit by rays. The first cost metric we present aims at constructing a single kd-tree that is used to trace both primary and secondary rays, whereas the second one is more relevant to secondary rays, involving reflection/refraction or shadowing, whose distribution properties differ from those for primary rays. Our experiments, using both CPU-based and GPU-based computation with several test scenes, demonstrate that the presented cost metrics can reduce markedly the cost of ray-traversal computation and increase significantly the overall frame rate for ray tracing.

Ray-Tracing Method를 이용한 일영면적 산정방식 고찰

최정민(Choi Jeong-Min),조성우(Cho Sung-Woo) 한국태양에너지학회 2011 한국태양에너지학회 논문집 Vol.31 No.3

Nowadays, the solar expose right is very important with people's life. Therefore, in calculating the sunshine hours, the point analysis and area analysis methods are used in previous studies. Previous two methods have merits and faults. Therefore, ray-tracing method is used as a alternative. Ray-tracing method is adopted by the software of Autodesk Ecotect which is a widely used program by the architectural company and academic university. In this study first, ray-tracing methodology is studied with how to calculate the overshadowing area and, secondly, the sensitivity of the two major factors, overshadowing accuracy and sky subdivision, is analyzed. With these results, appropriate application of the ray-tracing method is presented.

Real-time Ray-tracing Chip Architecture

Yoon, Hyung-Min,Lee, Byoung-Ok,Cheong, Cheol-Ho,Hur, Jin-Suk,Kim, Sang-Gon,Chung, Woo-Nam,Lee, Yong-Ho,Park, Woo-Chan The Institute of Electronics and Information Engin 2015 IEIE Transactions on Smart Processing & Computing Vol.4 No.2

In this paper, we describe the world's first real-time ray-tracing chip architecture. Ray-tracing technology generates high-quality 3D graphics images better than current rasterization technology by providing four essential light effects: shadow, reflection, refraction and transmission. The real-time ray-tracing chip named RayChip includes a real-time ray-tracing graphics processing unit and an accelerating tree-building unit. An ARM Ltd. central processing unit (CPU) and other peripherals are also included to support all processes of 3D graphics applications. Using the accelerating tree-building unit named RayTree to minimize the CPU load, the chip uses a low-end CPU and decreases both silicon area and power consumption. The evaluation results with RayChip show appropriate performance to support real-time ray tracing in high-definition (HD) resolution, while the rendered images are scaled to full HD resolution. The chip also integrates the Linux operating system and the familiar OpenGL for Embedded Systems application programming interface for easy application development.

큰 규모의 불규칙 조면에 의한 전자파 전파 특성

윤광렬,채용웅,Yoon Kwang-Yeol,Chai Yong-Yoong 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.4

In this paper we applied a ray tracing method to estimate the scattering characteristics from large scale random rough surfaces. For the electromagnetic field evaluation, we have used the diffracted coefficient of the knife edge diffraction for the diffracted rays and Fresnel's reflection coefficients in connection with reflected rays. In addition, we examine to search for the traced rays using the imaging method which can be obtained all rays to arrived at receivers accurately and the diffracted field from rough surfaces is considered. Numerical examples have been carried out for the scattering characteristics of an ocean wave-like rough surface and delay spread characteristics of a building-like surface. In the present work we have demonstrated that the ray tracing method is effective to numerical analysis of a rough surface scattering. 본 논문에서는 비교적 큰 규모의 불규칙 조면에 의한 산란 특성을 예측하기 위해 ray tracing 기법을 적용하였다. 전자계를 평가하기 위하여, 회절 레이(ray)에 대해서 knife edge 회절에 의한 회절 계수를 사용하였고, 반사 레이에 관해서는 Fresnel의 반사 계수를 사용하였다. 또한 레이 추적 방법에는 수신기에 도달하는 모든 레이의 경로를 정확히 찾아주는 image method를 채용하였으며, 불규칙 조면에 회절계를 고려하였다. 파도 모양의 조면에 의한 산란 특성과 빌딩 모양의 표면에 의한 지연 확산(delay spread) 특성에 대해 수치 계산하였다. 불규칙 조면에 의한 산란 특성을 수치적으로 해석하는데 ray tracing 기법을 적용하여 그 유효성을 입증하였다.