業績

2017年度

書籍

藤代 一成
コンピュータグラフィックス
電子情報通信学会100年史,第2部「電子情報通信技術100年の発展」,D:情報・システム,5章:映像メディア,2節 (374頁—377頁),2017年9月
PASJ2917
社団法人電子情報通信学会は2017年に創立100周年を迎え,その記念事業の一環として電子情報通信技術のこの一世紀に渡る進展を振り返る書籍:電子情報通信学会100年が刊行された.同書籍に収蔵された本解説は,コンピュータグラフィックス技術の進展ぶりをシステムの観点からまとめた後,モデリング,レンダリング,アニメーションという主要構成技術ごとに概説したものである.唯一の挿入図に掲載されたCGの手本形状Utahティーポットの画像3枚(左図(a)~(c))は,当ラボの中山 雅紀によって新たに作成されたものである.

国際学術誌(英文)

Makoto Uemura, Ryosuke Itoh, Ioannis Liodakis, Dmitry Blinov, Masanori Nakayama, Longyin Xu, Naoko Sawada, Hsiang-Yun Wu, Issei Fujishiro
Optical polarization variations in the blazar PKS 1749+096
PASJ, 2017
PASJ2917
We report on the variation in the optical polarization of the blazar PKS 1749+096 observed in 2008–2015. The degree of polarization (PD) tends to increase in short flares having a time-scale of a few days. The object favors a polarization angle (PA) of 40∘–50∘ at the flare maxima, which is close to the position angle of the jet (20∘–40∘). Three clear polarization rotations were detected in the negative PA direction associated with flares. In addition, a rapid and large decrease in the PA was observed in the other two flares, while another two flares showed no large PA variation. The light curve maxima of the flares possibly tend to lag behind the PD maxima and color-index minima. The PA became −50∘ to −20∘ in the decay phase of active states, which is almost perpendicular to the jet position angle. We propose a scenario to explain these observational features, where transverse shocks propagate along curved trajectories. The favored PA at the flare maxima suggests that the observed variations were governed by the variations in the Doppler factor, δ. Based on this scenario, the minimum viewing angle of the source, θmin=4.8∘–6.6∘, and the location of the source, Δr≳0.1pc, from the central black hole were estimated. In addition, the acceleration of electrons by the shock and synchrotron cooling would have a time-scale similar to that of the change in δ. The combined effect of the variation in δ and acceleration/cooling of electrons is probably responsible for the observed diversity of the polarization variations in the flares.

国内学術誌(和文)

湯浅 海貴中山 雅紀藤代 一成
Swellart:制約付き膨張によるスケッチベースのデフォルメデザイン
芸術科学会論文誌, Vol. 16, No. 4, pp. 102-109, 2017年11月.
CGI2017Sawada
本研究では,初心者でも直感的にデフォルメされた2Dグラフィックデザインを生成できるシステム—Swellartを提案する.我々は,システムを開発するうえで,変形の方法のなかでも膨張に着目している.ユーザが描画した枠の形状に合わせて対象の画像が膨張する過程を単純に示すことで,すべてのユーザが容易に変形過程やその結果を想像させられる.膨張方法として,まずユーザが画像を指定して,デフォルメしたい範囲をユーザがくり抜き,その範囲内のメッシュ分割を行う.次に,分割された各セルに対しさまざまな制約をユーザが指定して膨張を行うことで,多様なデフォルメデザインを生成できる.本論文では,Swellart の処理手順と結果を示し,今後の方向性を議論する.

国際会議録論文

Atsushi Miyazawa, Masanori Nakayama, Issei Fujishiro
Immersive Math Environment Continuable to Cross-sectional Complex Projective 2-space
in Proceedings of the 11th Asian Forum on Graphic Science,
Article No. F40, Tokyo (Japan), 2017
because to depict a pair of complex numbers we would need four dimensions
Constructing the graph of the complex square root function around its singular point in terms of polar coordinates
What does the Riemann sphere’s axis stand for?
As is well-known, in quantum mechanics the complex wave plays an essential role, which can explain the natural phenomena very well. In other words, it can be said that the rules of nature are written with logic using complex numbers. We are accustomed to the convenience of visualizing the overall behavior of a function by means of its graph. In the case of a complex function, however, this approach has not seemed workable for a long time because to depict a pair of complex numbers (an input z and the output of a function f ) we would need four dimensions.

Especially in mathematical visualization, we have demonstrated thus far that how the fourth dimension is conceptualized seems to be successfully justified by using a cross section and a projection of an object appropriately, described in terms of polar coordinates (instead of Cartesian coordinates).

And we raise the question that has been neglected thus far: “What does the Riemann sphere’s axis stand for?” We show that the answer can be obtained only by observing from the inside the sphere by setting the viewpoint of the immersive environment on the point (0, 0), which is always undefined in projective geometry.


Naoko Sawada, Masanori NakayamaHsiang-Yun Wu, Makoto Uemura, Issei Fujishiro
TimeTubes: Visual Fusion and Validation for Ameliorating Uncertainties of Blazar Datasets from Different Observatories
in Proceedings of the Computer Graphics International Conference,
Article No. 14, Yokohama (Japan), 2017
CGI2017Sawada
Astronomers have been observing blazars to solve the mystery of the relativistic jet. A technique called TimeTubes uses a 3D volumetric tube to visualize the time-dependent multivariate observed datasets and allows astronomers to interactively analyze the dynamic behavior of and relationship among those variables. However, the observed datasets themselves exhibit uncertainty due to their errors and missing periods, whereas periods interpolated by TimeTubes result in a different type of uncertainty. In this paper, we present a technique for ameliorating such data- and mapping-inherent uncertainties: visual fusion of datasets for the same blazar from two different observatories. Visual data fusion with Time-Tubes enables astronomers to validate the datasets in a meticulous manner.

Hsiang-Yun Wu, Yusuke Niibe, Kazuho Watanabe, Shigeo Takahashi, Makoto Uemura, Issei Fujishiro
Making Many-to-Many Parallel Coordinate Plots Scalable by Asymmetric Biclustering
in Proceedings of IEEE Pacific Visualization 2017, Seoul (Korea), 2017
many-to-many2017
Datasets obtained through recently advanced measurement techniques tend to possess a large number of dimensions. This leads to explosively increasing computation costs for analyzing such datasets, thus making formulation and verification of scientific hypotheses very difficult. Therefore, an efficient approach to identifying feature subspaces of target datasets, that is, the subspaces of dimension variables or subsets of the data samples, is required to describe the essence hidden in the original dataset. This paper proposes a visual data mining framework for supporting semiautomatic data analysis that builds upon asymmetric biclustering to explore highly correlated feature subspaces. For this purpose, a variant of parallel coordinate plots, many-to-many parallel coordinate plots, is extended to visually assist appropriate selections of feature subspaces as well as to avoid intrinsic visual clutter. In this framework, biclustering is applied to dimension variables and data samples of the dataset simultaneously and asymmetrically. A set of variable axes are projected to a single composite axis while data samples between two consecutive variable axes are bundled using polygonal strips. This makes the visualization method scalable and enables it to play a key role in the framework. The effectiveness of the proposed framework has been empirically proven, and it is remarkably useful for many-to-many parallel coordinate plots.

国際コンテスト

Masanori Nakayama, Issei Fujishiro
Duality
Asian Digital Modeling Contest 2017, Tokyo, August 7-10, 2017 (Grand Prize).
In the present work, we attempted at expressing human “two-facedness” by the “two-sidedness” of the 3D structures. In the field of geometry, there exists a two-facedness called “duality,” which represents the relationship between diagrams that switch between faces (cells) and vertices. Delaunay diagram and Voronoi diagram give a typical example. We have developed an algorithm to generate a Poisson-disk distribution in an arbitrary shape to make sculptures with those diagrams. The Delaunay diagram generated by Poisson-disk distribution point cloud makes up the uniform tetrahedral mesh (except for the surface). Since those cells are close to a regular tetrahedron, Voronoi vertices located on the circumcenters also have an almost uniform distribution.

国際会議ポスタ(査読付)

Naoko Sawada, Masanori NakayamaHsiang-Yun Wu, Makoto Uemura, Issei Fujishiro
TimeTubes: Visual Fusion for Ameliorating Uncertainty of Blazar Datasets from Different Observatories
IEEE Pacific Visualization 2017 Poster Session
SidebySideCaption
Blazars are active galactic nuclei whose relativistic jets ejected from the central black hole are pointing toward the Earth. Astronomers have attempted to classify blazars, whereas it is difficult to analyze the time-dependent multivariate datasets with the conventional visualization methods, such as animeted scatterplot matrices. In our previous study, a new visualization scheme, called TimeTubes, was proposed, which allows the astronomers to analyze dynamic changes in and feature causality among the multiple time-varying variables. In this poster, we present a core idea to ameliorate data-inherent and mapping-inherent uncertainty through visual fusion of datasets for the same blazar from two different observatories.


国内会議論文(査読付)

池田 泰成都甲 裕太朗藤代 一成
糸の微細構造を考慮した細かな毛羽立ちをもつパイル織物の生成手法
NICOGRAPH 2017

学会ページへ

コンピュータグラフィックス(CG)において糸を細部まで忠実に再現することは,困難な課題として知られている.糸は織物や編み物,衣服を構成するために必要であり,現実世界を仮想空間に再現するために不可欠な素材である.これまでに開発された糸の生成手法は,ボリュームベースと繊維ベースの二種類に分類できる.近年提案された繊維ベース手法では,糸の断面を CT スキャンし,その細部を精密に表現している.近年の先進的な手法により,CG における糸の表現力は劇的に向上し,なおかつその生成に必要なコストも減少した.しかし,糸の周囲に生える毛羽立ちの生成プロセスは,未だに挑戦的な課題である.特に,表面の毛羽立ちが独特な形状となるパイル織物は,タオルや車のシートなど生活のあらゆる場所で使用される一般的な素材であるにも関わらず,既存のフレームワークでは表現が不可能である.加えて,上述した繊維ベース手法では糸の生成プロセスに注目していたが,その糸を使用した織物の生成フレームワークについては,筆者らの知る限り未だに提案されていない.これらの課題を解決するため,本論文では既存のフレームワークを拡張することでパイル繊維をもつ糸の生成に対応するとともに,この糸から自動的にパイル織物を生成する手法を提案する.

総説

藤代 一成
知的環境メディア
画像電子学会誌,46巻,4号,585頁—589頁,2017年10月30日
知的環境メディア(smart ambient media, SAM)とは,マルチモーダルセンシング ―知的計算― 適応的レンダリングを利用して,我々の日常生活の諸活動を巧みに支援する表示手法を総称したものである.本解説では,SAMの一般的な枠組みを示した後,当研究室の関連研究開発事例を6点紹介し,関連する諸概念にも言及している.さらにこれらの事例を特徴づけ,SAMに共通する特徴とその可能性を明らかにしている.

国内会議

中田 聖人藤代 一成
器官の準解剖学的データを用いた手のモデリング
Visual Computing/グラフィクスとCAD 合同シンポジウム2017(ポスタ発表),2017年6月
学会ページへ

篠﨑 紗衣子中山 雅紀藤代 一成
異方性をもつ紙繊維シートの破断シミュレーション
Visual Computing/グラフィクスとCAD 合同シンポジウム2017(ポスタ発表),2017年6月
学会ページへ

堀井 絵里藤代 一成
音源に同期する運指に注目した吹奏アニメーションの自動生成
Visual Computing/グラフィクスとCAD 合同シンポジウム2017(ポスタ発表),2017年6月
学会ページへ

高倉 優理子中山 雅紀小島 有利子藤代 一成
スペクトル楽派の作曲家を対象とした音響加工過程に関する視覚分析手法の提案
研究報告音楽情報科学(MUS)(ポスタ発表),2017-MUS-115(36),pp. 1-6,2017年6月
学会ページへ

口頭発表

Naoko Sawada, Masanori Nakayama, Hsiang-Yun Wu, Makoto Uemura, Issei Fujishiro
TimeTubes: Visual Fusion for Detailed and Precise Analysis of Time-Varying Multi-Dimensional Datasets
in Proceedings of the International Meeting on “High-Dimensional Data-Driven Science”, September 2017