Controllable local monotonic cubic interpolation in fluid animations

Ihm, Insung,Cha, Deukhyun,Kang, Byungkwon John Wiley Sons, Ltd. 2005 Computer Animation and Virtual Worlds Vol. No.

<P>While linear interpolation has been used frequently in computer graphics, higher-order interpolation is often desirable in applications requiring higher-order accuracy. In this paper, we study how interpolation filters, employed to resample such data as velocity, density, and temperature in simulating the equations of fluid dynamics, affect the animation of fluids. For this purpose, we have designed a controllable local cubic interpolation scheme that offers G<SUP>1</SUP> (or C<SUP>1</SUP>) continuity globally. It is based on monotonic splines so does not suffer from undue overshooting. Furthermore, it is possible to control the general behavior of the interpolation through a global tension parameter, providing a continuous spectrum of linear to cubic interpolation. We analyze how this controllable interpolation filter may be effectively used to enhance the visual reality for physically based fluid animation. Copyright © 2005 John Wiley & Sons, Ltd.</P>

Extending the photon mapping method for realistic rendering of hot gaseous fluids

Kang, Byungkwon,Ihm, Insung,Bajaj, Chandrajit John Wiley Sons, Ltd. 2005 Computer Animation and Virtual Worlds Vol. No.

<P>With the increased sophistication and use of heated gas, fire, and explosion simulations in computer graphics applications, there is a corresponding impetus to improve the visual realism in the rendering of such simulated phenomena. In visualizing these turbulent fluids, an appropriate incorporation of their incandescent properties into the rendering significantly enhances the realism of visual effects. In this paper, we effectively synthesize the light emission phenomena of hot gaseous fluids by extending the photon mapping global illumination method. In particular, we add two new photon maps to capture the thermal radiation effects. First, we define an emission photon map to store the photons emitted within hot gaseous fluids. Second, we utilize additional flash and flash reflection photon maps, which are effective in creating a visual effect of light that intensively and instantly propagates outside hot gaseous fluids, visually capturing shock waves. Our current technique, while based on the theory of blackbody radiation, is parameterized to enable an animator to generate a wide range of visual effects with fairly intuitive user control. We demonstrate the effectiveness of our new rendering technique and user-controlled generation of visual effects with several example pictures and animations. Copyright © 2005 John Wiley & Sons, Ltd.</P>

Chemical kinetics-assisted, path-based smoke simulation

Jang, Yoojin,Ihm, Insung John Wiley Sons, Ltd. 2009 COMPUTER ANIMATION AND VIRTUAL WORLDS Vol.20 No.2

<P>Despite recent successes in physics-based fluid animation, generating desired fluid flow with intuitive control of its motion still remains a challenging problem in the special effects industry. In this paper, we propose a novel approach for path-based smoke simulation that explores the theory of chemical kinetics in an aim to provide a useful animation tool. By describing intended smoke effects through chemical reaction equations and adjusting their parameters, our method allows to easily create various interesting smoke effects that were often hard to get with previous techniques. To demonstrate the effectiveness of the presented animation framework, we describe several examples of path-based smoke animations, generated with easily understandable reaction equations and control parameters. Copyright © 2009 John Wiley & Sons, Ltd.</P> <B>Graphic Abstract</B> <P>This paper presents a novel approach for path-based smoke simulation that explores the theory of chemical kinetics in an aim to provide a useful animation tool. By describing intended smoke effects through chemical reaction equations and adjusting their parameters, it allows to easily create various interesting smoke effects that were often hard to get with previous techniques. We describe several examples of path-based smoke animations, generated with easily understandable reaction equations and control parameters. <img src='wiley_img/15464261-2009-20-2-3-CAV286-gra001.gif' alt='wiley_img/15464261-2009-20-2-3-CAV286-gra001'> </P>

포톤 매핑 기법을 이용한 폭발 및 화염의 사실적인 렌더링 기법

강병권(Byungkwon Kang),임인성(Insung Ihm) 한국컴퓨터그래픽스학회 2004 컴퓨터그래픽스학회논문지 Vol.10 No.3

GPU용 Kd-트리 탐색 방법의 성능 분석 및 향상 기법

장병준(Byungjoon Chang),임인성(Insung Ihm) 한국정보과학회 2010 정보과학회 컴퓨팅의 실제 논문지 Vol.16 No.2

광선-다각형 교차 계산은 광선 추적법 계산의 상당 부분을 차지하는 중요한 구성요소로서, 보편적으로 정적인 장면에 대해서는 kd-트리와 같은 공간 자료구조를 사용하여 교차 계산을 가속하여왔다. 최근 CPU에 비해 상대적으로 제한된 계산구조를 가지는 GPU에 적합하도록 변형된 kd-트리 탐색 기법이 몇 가지 제시되어 왔는데, 본 논문에서는 이러한 기존 방법을 보완할 수 있는 두 가지 구현 기법을 제안한다. 첫째, 트리 탐색을 위한 스택을 전역 메모리에 할당할 경우 전역 메모리 접근으로 인한 비용을 줄이고자 하는 캐쉬 적용 스택 방법과 둘째, 기존의 로프 방법의 문제점인 상당한 메모리 요구량을 줄이고자 하는 적은 깊이의 스택(short stack)을 사용한 로프 방법을 제시한다. 제안된 방법의 효용성을 보이기 위하여 기존의 GPU용 탐색 방법과의 성능 비교 분석을 수행한다. 이러한 실험 결과는 향후 GPU용 광선 추적법 소프트웨어 개발자들이 상황에 맞는 적절한 kd-트리 탐색 방법을 선택할 수 있도록 해주는 중요한 정보를 제공하게 될 것이다. Ray-object intersection is an important element in ray tracing that takes up a substantial amount of computing time. In general, such spatial data structure as kd-tree has been frequently used for static scenes to accelerate the intersection computation. Recently, a few variants of kd-tree traversal have been proposed suitable for the GPU that has a relatively restricted computing architecture compared to the CPU. In this article, we propose yet another two implementation techniques that can improve those previous ones. First, we present a cached stack method that is aimed to reduce the costly global memory access time needed when the stack is allocated to global memory. Secondly, we present a rope-with-short-stack method that eases the substantial memory requirement, often necessary for the previous rope method. In order to show the effectiveness of our techniques, we compare their performances with those of the previous GPU traversal methods. The experimental results will provide prospective GPU ray tracer developers with valuable information, helping them choose a proper kd-tree traversal method.

이미지 와핑을 이용한 실시간 그림자 생성 기법

강병권(Byungkwon Kang),임인성(Insung Ihm) 한국정보과학회 2002 정보과학회논문지 : 시스템 및 이론 Vol.29 No.5·6

컴퓨터 그래픽스에서 그림자는 장면의 사실성을 높이기 위하여 매우 중요한 요소이다. 전경을 렌더링 할 때 그림자의 모양이나 위치를 정확하게 나타내는 것도 중요하지만, 실제 세계에서 흔히 볼 수 있는 면적을 가지는 광원에 의한 부드러운 그림자를 효과적으로 표현하는 것도 중요하다. 그러나 현존하는 대부분의 그림자 생성 기법들은 사실적인 그림자를 실시간으로 생성해 내기에 어려움이 많다. 기존에 제안된 영상 기반 렌더링 기법을 이용하면 실시간으로 그림자를 생성해 내는데 유용하게 사용될 수가 있다. 하지만 이러한 방법에서는 일반적으로 그림자 지도의 크기가 지나치게 방대해지기 때문에, 텍스춰 메모리에 올리기에 무리가 따르게 되므로, 효율적인 압축기법이 필요하다는 단점이 있다. 이러한 그림자 지도의 크기와 압축의 부담으로 인해, 다양한 물체의 움직임을 표현하거나, 부드러운 그림자로의 확장에 어려움이 있을 수 있다. 이러한 점을 해결하고자, 본 논문에서는 영상 기반 렌더링 기법을 적용한 방법에 이미지 와핑 기법을 응용하여 그림자 지도의 크기를 대폭 줄일 수 있는 방법을 제안하고자 한다. 이 방법에서는 물체가 움직이는 범위와 상관없이 매우 적은 개수의 그림자 지도만으로 그림자를 만들어 낼 수 있기 때문에, 부드러운 그림자를 만들기 위한 방법으로 쉽게 적용할 수 있다. 이 논문에서 개발한 기법은 3차원 게임이나 가상 현실 등 관련 분야에서 사실적인 영상을 실시간으로 생성해 내는 데 유용하게 쓰일 수 있을 것이다 Shadows are important elements in producing a realistic image. Generation of exact shapes and positions of shadows is essential in rendering since it provides users with visual cues on the scene. It is also very important to be able to create soft shadows resulted from area light sources since they increase the visual realism drastically. In spite of their importance, the existing shadow generation algorithms still have some problems in producing realistic shadows in real-time. While image-based rendering techniques can often be effectively applied to real-time shadow generation, such techniques usually demand so large memory space for storing preprocessed shadow maps. An effective compression method can help in reducing memory requirement, only at the additional decoding costs. In this paper, we propose a new image-based shadow generation method based on image warping. With this method, it is possible to generate realistic shadows using only small sizes of pre-generated shadow maps, and is easy to extend to soft shadow generation. Our method will be efficiently used for generating realistic scenes in many real-time applications such as 3D games and virtual reality systems.

GPU-Assisted High Quality Particle Rendering

Cha, Deukhyun,Son, Sungjin,Ihm, Insung Blackwell Publishing Ltd 2009 Computer graphics forum Vol.28 No.4

<P>Abstract</P><P>Visualizing dynamic participating media in particle form by fully solving equations from the light transport theory is a computationally very expensive process. In this paper, we present a computational pipeline for particle volume rendering that is easily accelerated by the current GPU. To fully harness its massively parallel computing power, we transform input particles into a volumetric density field using a GPU-assisted, adaptive density estimation technique that iteratively adapts the smoothing length for local grid cells. Then, the volume data is visualized efficiently based on the volume photon mapping method where our GPU techniques further improve the rendering quality offered by previous implementations while performing rendering computation in acceptable time. It is demonstrated that high quality volume renderings can be easily produced from large particle datasets in time frames of a few seconds to less than a minute.</P>

Generation of Non-uniform Meshes for Finite-Difference Time-Domain Simulations

Hyeong-Seok Kim,Insung Ihm,Kyung Choi 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.1

In this paper, two automatic mesh generation algorithms are presented. The methods seek to optimize mesh density with regard to geometries exhibiting both fine and coarse physical structures. When generating meshes, the algorithms attempt to satisfy the conditions on the maximum mesh spacing and the maximum grading ratio simultaneously. Both algorithms successfully produce non-uniform meshes that satisfy the requirements for finite-difference time-domain simulations of microwave components. Additionally, an algorithm successfully generates a minimum number of grid points while maintaining the simulation accuracy.

Ray tracing-based interactive diffuse indirect illumination

Chang, Byungjoon,Park, Sanghun,Ihm, Insung Springer-Verlag 2016 MULTIMEDIA TOOLS AND APPLICATIONS Vol.75 No.12

<P>Despite great efforts in recent years to accelerate global illumination computation, the real-time ray tracing of fully dynamic scenes to support photorealistic indirect illumination effects has yet to be achieved in computer graphics. In this paper, we propose an extended ray tracing model that can be readily implemented on a GPU to facilitate the interactive generation of diffuse indirect illumination, the quality of which is comparable to that generated by the traditional, time-consuming photon mapping method and final gathering. Our method employs three types of (multilevel) grids to represent the indirect light in a scene using a form that facilitates the efficient estimation of the reflected radiance caused by diffuse interreflection. This method includes the mathematical tool of spherical harmonics and a rendering scheme that performs the final gathering step with a minimal cost during ray tracing, which guarantees the interactive frame rates. We evaluated our technique using several dynamic scenes with nontrivial complexity, which demonstrated its effectiveness.</P>

Diffuse global illumination in particle spaces

Chang, Byungjoon,Park, Sanghun,Ihm, Insung Springer-Verlag 2015 MULTIMEDIA TOOLS AND APPLICATIONS Vol.74 No.13