研究成果

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[Course] An Elementary Introduction to Matrix Exponential for CG
Hiroyuki Ochiai, Ken Anjyo, Ayumi Kimura
SIGGRAPH '16 ACM SIGGRAPH 2016 Courses Article No. 4 (The movie and talk slides are available)
This course presents an elementary, intuitive, and visual introduction to several mathematical basics for beginners in computer graphics. The mathematical concepts covered in this course include 2D/3D translation, rotation, affine transformation, quaternion, dual quaternion, exponential and logarithm. These are quite useful for various aspects of computer graphics, including curve/surface editing,...
[journal] Fluid Volume Modeling from Sparse Multi-view Images by Appearance Transfer
Makoto Okabe, Yoshinori Dobashi, Ken Anjyo, Rikio Onai
ACM Transactions on Graphics, volume 34, issue 4 (Proc. SIGGRAPH 2015), pp. 93:1-93:10
We propose a method of three-dimensional (3D) modeling of volumetric fluid phenomena from sparse multi-view images (e.g., only a single-view input or a pair of front- and side-view inputs). The volume determined from such sparse inputs using previous methods appears blurry and unnatural with novel views; however, our method preserves the appearance of novel viewing angles by transferring the appea...
[Course] Mathematical Basics of Motion and Deformation in Computer Graphics
Ken Anjyo, Hiroyuki Ochiai
SIGGRAPH '14 ACM SIGGRAPH 2014 Courses Article No. 19 (The talk slides and course notes are available. 2014.8.20)
While many technical terms, such as Euler angle, quaternion, and affine transformation, are now quite popular in computer graphics, their graphical meanings are sometimes a bit far from the original mathematical entities, which could cause misunderstanding or misuse of the mathematical techniques. The concepts are inherited mostly from differential geometry and Lie theory, and are now commonly use...
[Course] Mathematical Description of Motion and Deformation: From Basics to Graphics Applications
Hiroyuki Ochiai, Ken Anjyo
SIGGRAPH ASIA 2013, Proceeding SIGGRAPH Asia 2013 Courses Article No. 2 (The revised course notes and talk slides are available. (04/12/2013))
While many technical terms, such as Euler angle, quaternion, and affine transformation, now become quite popular in computer graphics, their graphical meanings are sometimes a bit far from the original mathematical entities, which might cause misunderstanding or misuse of the mathematical techniques. This course presents an intuitive introduction to several mathematical concepts that are quite use...
[Invited Talk] Digital animation techniques and high performance computing
Ken Anjyo
Northeastern Asian Symposium: Method and Modeling for High performance Scientific Computing, Chengdu, China, 2013.9
In the film, video game and animation industries, the ultimate goal is not a completely physics-based reality but a plausible, believable reality. In this talk, I will describe a few of our recent research work that should meet such practical demands in creating elastic body animation and realistic facial animation. Considering these research efforts, I will also discuss the role of high-performan...
[Proceedings] Generating Variations of Flow Fields by Modulating Amplitude and Resizing Simulation Space
Syuhei Sato, Yoshinori Dobashi, Kei Iwasaki, Hiroyuki Ochiai, Tsuyoshi Yamamoto
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 15-20, 2013.10
[Proceedings] Single-view 3D Reconstruction by Learning 3D Game Scenes
Makoto Okabe, Ken Anjyo, Rikio Onai
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 39-42, 2013.10
[Proceedings] Probable and Improbable Faces
J.P. Lewis, Ken Anjyo, Zhenyao Mo, Taehyun Rhee
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 43-49, 2013.10
[Proceedings] Efficient Image-based Rendering Method using Spherical Gaussian
Kei Iwasaki
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 52-55, 2013.10
[Proceedings] A Lie Theoretic Proposal on Algorithms for Spherical Harmonic Lighting
Masato Wakayama
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 56-63, 2013.10
[Proceedings] Inverse Approach for Visual Simulation of Clouds
Yoshinori Dobashi
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 78-83, 2013.10
[Proceedings] Mathematical Formulation of Motion/Deformation and its Applications
Hiroyuki Ochiai, Ken Anjyo
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 100-103, 2013.10
[Proceedings] Ray Tracing of Quadratic Parametric Surface
Shinji Ogaki
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 110-115, 2013.10
[Proceedings] Anti-commutative Dual Complex Numbers and 2D Rigid Transformation
Genki Matsuda, Shizuo Kaji, Hiroyuki Ochiai
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 128-133, 2013.10
[Proceedings] A Lie Theoretic Parameterization of Affine Transformation
Shizuo Kaji, Sampei Hirose, Hiroyuki Ochiai, Ken Anjyo
Proceedings of Symposium MEIS2013, MI LectureNote, Vol. 50, pp. 134-140, 2013.10
[Journal] Line Selection Tool for 3D Artists
Jaewoo Seo & Ken Anjyo
Journal of Graphics Tools, Volume 16, Issue 4, pp. 233-244, 2013.9 PDF | DOI
Mesh component selection is one of the most common tasks in the 3D modeling process. However, even the latest 3D software packages still lack high-level component selection schemes. This makes users suffer from frequent mouse actions with precise control. We present a tool to select a set of vertices or edges along a line in the given mesh with ease. Because it mimics the behavior of the boundary ...
[Journal] A Practical Approach to Direct Manipulation Blendshapes
Ken Anjyo, Hideki Todo, J.P. Lewis
Journal of Graphics Tools, Volume 16, Issue 3, 2012, pp. 160-176 PDF | DOI
The original approach of direct manipulation blendshapes introduced a mathematical framework for manipulating blendshape face models directly and interactively while interoperating with traditional slider-based editing. This article introduces a few practical and useful techniques to the original work and presents the implementation details as a software tool. In addition, this article describes a...
[Talk] An Application of Lie theory to Computer Graphics
Shizuo Kaji
Applied Topology, Będlewo, Poland, 2013.7
In computer graphics, various mathematics is used such as the Navie-Stokes equations for generating clouds and fires, reproducing kernel Hilbert space for mixing different facial expressions, and piecewise linear map (PL-map, in short) for morphing shapes. I will discuss an algorithm to blend/deform shapes based on PL-map and an elementary Lie theory. A shape is represented by a polyhedron and its...
[Invited Talk] Techniques for making animation directable
Ken Anjyo
Proceedings of the 29th Spring Conference on Computer Graphics, Smolenice, Slovakia, 2013.5
In the film, video game or animation industries, the ultimate goal is not to provide completely physics-based reality but a plausible reality. We therefore need to explore the techniques and methodologies of making digital images and animation directable, blending art-directed expressions with physics-based depictions. In this talk, I will describe some of our recent research work that are intende...
[Journal] Lit-Sphere extension for artistic rendering
Hideki Todo, Ken Anjyo, Shun'ichi Yokoyama
The Visual Computer, Volume 29, Issue 6 (2013), pp. 473-480 PDF | DOI
The Lit-Sphere model proposed by Sloan et al. (Proceedings of Graphics Interface 2001, pp. 143–150, 2001) is a method for emulating expressive artistic shading styles for 3D scenes. Assuming that artistic shading styles are described by view space normals, this model produces a variety of stylized shading scenes beyond traditional 3D lighting control. However, it is limited to the static lightin...
[Conference] Video Retrieval based on User-Specified Appearance and Application to Animation Synthesis
Makoto Okabe, Yuta Kawate, Ken Anjyo, Rikio Onai
Proceedings of 19th International Conference on Multimedia Modeling, MMM 2013, Part II, pp. 110-120, Multimedia Retrieval and Management with Human Factors, Special Session Papers, Huangshan, China, 2013.1 PDF | DOI
In our research group, we investigate techniques for retrieving videos based on user-specified appearances. In this paper, we introduce two of our research activities.

First, we present a user interface for quickly and easily retrieving scenes of a desired appearance from videos. Given an input image, our system allows the user to sketch a transformation of an object inside the image, and then ...
[Invited Talk]Visual Simulation of Clouds - Inverse Design Approach -
Yoshinori Dobashi
Asian Conference on Design and Digital Engineering, Hokkaido Niseko, 2012.12
When creating synthetic images of outdoor scenes, clouds play important roles to enhance the realism. The research on the synthesis of realistic clouds has a long history and has attracted many researcher's interest. In this talk, I would present our researches on the visual simulation of clouds. Topics included in this talk are simulation and control of cloud motion using cellular automata/fluid ...
[Conference] Real-time rendering of animated hair under dynamic, low-frequency environmental lighting
Xiaoxiong Xing, Yoshinori Dobashi, Tsuyoshi Yamamoto, Yosuke Katsura, Ken Anjyo
Proceedings of Virtual Reality Continuum and its Application in Industry (VRCAI 2012), pp. 43-46, 2012.12 PDF | DOI
We present a fast algorithm for rendering animated hair under a dynamic lighting environment at interactive frame rates. We use spherical harmonics (SH) to represent the environmental lighting. Since SH functions are orthogonal, the environmental light is converted into an SH representation in real time. To compute hair shadows efficiently, the transmittances between a point on a hair strand and t...
[Conference] Feature-based interpolation for the interactive editing of shading effects
Munehiro Tada, Yoshinori Dobashi, Tsuyoshi Yamamoto
Proceedings of Virtual Reality Continuum and its Application in Industry (VRCAI 2012), pp. 47-50, 2012.12 PDF | DOI
In computer graphics, shading techniques play an important role when displaying realistic virtual objects. Although physically-based techniques can generate realistic results, it is often difficult to produce desired shading effects. Therefore, artists usually creates desired shading effects by manually placing many virtual light sources. However, this is not an easy task since it is difficult to ...
[Conference] Visual simulation of freezing ice with air bubbles
Takanori Nishino, Kei Iwasaki, Yoshinori Dobashi, Tomoyuki Nishita
SIGGRAPH ASIA 2012, Technical Brief, Article No. 1, 2012.11 PDF | DOI
Ice often contains small air bubbles that are dissolved air exhausted from water-ice interface. Depicting these air bubbles with various sizes enhances the realism of ice. This paper proposes a fast simulation method of freezing ice taking into account air bubbles. Our method introduces a physically-based calculation method of the sizes of air bubbles based on the freezing velocity and pressure. I...
[Poster] Keyframe Control of Cumulus Cloud Simulation
Katsutoshi Kusumoto, Yoshinori Dobashi, Tsuyoshi Yamamoto
ACM SIGGRAPH ASIA 2012 Poster Program, 2012.11
Clouds play an important role when creating realistic images of outdoor scenes. One of the most effective approaches for synthesizing realistic clouds is to simulate the cloud formation processes based on fluid dynamics. However, the resulting shapes of clouds depend on many simulation parameters. Therefore, it is difficult to adjust those parameters so that the clouds form the desired shapes. Thi...
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