Research OLM Digital R&D

Papers

Japan Journal of Industrial and Applied Mathematics

A linear algorithm for Brick Wang tiling

Alexandre Derouet-Jourdan, Shizuo Kaji, Yoshihiro Mizoguchi

The Wang tiling is a classical problem in combinatorics. A major theoretical question is to find a (small) set of tiles which tiles the plane only aperiodically. In this case, resulting tilings are rather restrictive. On the other hand, Wang tiles are used as a tool to generate textures and patterns in computer graphics. In these applications, a set of tiles is normally chosen so that it tiles the plane or its sub-regions easily in many different ways. With computer graphics applications in mind, we introduce a class of such tileset, which we call sequentially permissive tilesets, and consider tiling problems with constrained boundary. We apply our methodology to a special set of Wang tiles, called Brick Wang tiles, introduced by Derouet-Jourdan et al. in 2016 to model wall patterns. We generalise their result by providing a linear algorithm to decide and solve the tiling problem for arbitrary planar regions with holes.

PDF

Eurographics 2019

MegaViews: Scalable Many-View Rendering with Concurrent Scene-View Hierarchy Traversal

Timothy R. Kol, Pablo Bauszat, Sungkil Lee, Elmar Eisemann

We present a scalable solution to render complex scenes from a large amount of viewpoints. While previous approaches rely either on a scene or a view hierarchy to process multiple elements together, we make full use of both, enabling sublinear performance in terms of views and scene complexity. By concurrently traversing the hierarchies, we efficiently find shared information among views to amortize rendering costs. One example application is many-light global illumination. Our solution accelerates shadow map generation for virtual point lights, whose number can now be raised to over a million while maintaining interactive rates.

Eurographics 2019

Generating Stochastic Wall Patterns On-the-Fly with Wang Tiles

Alexandre Derouet-Jourdan, Marc Salvati, Théo Jonchier

The game and movie industries always face the challenge of reproducing materials. This problem is tackled by combining illumination models and various textures (painted or procedural patterns). Generating stochastic wall patterns is crucial in the creation of a wide range of backgrounds (castles, temples, ruins...). A specific Wang tile set was introduced previously to tackle this problem, in an iterative fashion. However, long lines may appear as visual artifacts. We use this tile set in a new on-the-fly procedure to generate stochastic wall patterns. For this purpose, we introduce specific hash functions implementing a constrained Wang tiling. This technique makes possible the generation of boundless textures while giving control over the maximum line length. The algorithm is simple and easy to implement, and the wall structure we get from the tiles allows to achieve visuals that reproduce all the small details of artist painted walls.

PDF

JCGT 2019

Implementation of Fast and Adaptive Procedural Cellular Noise

Théo Jonchier, Alexandre Derouet-Jourdan, Marc Salvati

Cellular noise as defined by Worley is a useful tool to render natural phenomena, such as skin cells, reptiles scales, or rock minerals. It is computed at each position in texture space by finding the closest feature points in a grid. In a preliminary work, we showed in 2D space how to obtain non-uniform distribution of points by subdividing cells in the grid and that there is an optimal traversal order of the grid cells. In this paper, we generalize these results to higher dimensions, and we give details about their implementation. Our optimal traversal in 3D proves to be 15% to 20% faster than the standard Worley algorithm.
Journal of Computer Graphics Techniques (JCGT), vol. 8, no. 1, 35-44, 2019

Proceedings of the Royal Society of London A

Inverse design of an isotropic suspended Kirchhoff rod

Inverse design of an isotropic suspended Kirchhoff rod: theoretical and numerical results on the uniqueness of the natural shape

Florence Bertails-Descoubes, Alexandre Derouet-Jourdan, Victor Romero and Arnaud Lazarus

Solving the equations for Kirchhoff elastic rods has been widely explored for decades in mathematics, physics and computer science, with significant applications in the modeling of thin flexible structures such as DNA, hair, or climbing plants. The natural curvature plays an important role in the equilibrium shape of a Kirchhoff rod. In this paper, we characterize the natural curvature of a suspended isotropic rod, given an equilibrium curve. We prove that all natural curvatures that are compatible with the prescribed equilibrium are equivalent in the sense that they correspond to a unique natural shape for the rod.
Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences

MEIS2016

Dappled tiling

Shizuo Kaji, Alexandre Derouet-Jourdan, and Hiroyuki Ochiai

Abstract We consider a certain tiling problem of a planar region in which there are no long horizontal or vertical strips consisting of copies of the same tile. Intuitively speaking, we would like to create a dappled pattern with two or more kinds of tiles. We give an efficient algorithm to turn any tiling into one satisfying the condition, and discuss its applications in texturing.
Symposium MEIS2016: Mathematical Progress in Expressive Image Synthesis

MEIS2016

Procedural Non Uniform Cellular Noise

Theo Jonchier, Marc Salvati and Alexandre Derouet-Jourdan

Procedural cellular textures have been widely used in movie production to reproduce various natural and organic looks. The advantage of procedural texture is to trade memory for computer power and obtain potentially unlimited resolution. In this paper, we propose to compute non-uniform density cellular noise by using a procedural quad-tree. We will explain how to efficiently traverse the tree recursively (CPU) and iteratively (CPU and GPU).
Symposium MEIS2016: Mathematical Progress in Expressive Image Synthesis

SIGGRAPH 2015

Fluid Volume Modeling from Sparse Multi-view Images by Appearance Transfer

Makoto Okabe, Yoshinori Dobashi, Ken Anjyo, Rikio Onai

We model the natural-looking volume of fluids from sparse multi-view images (only a single-view or a pair of front and side views). We create the production-ready fluid animation using a volume sequence of fluids modeled from sparse multi-view videos. A fluid simulator allows users to further edit the appearance, behaviour, and shape of fluids (adding more turbulence).
ACM Transactions on Graphics (Proc. SIGGRAPH 2015), Vol 34, No 4, pp. 93:1-93:10

MOVIE PROJECT-PAGE

EGSR 2015

MBVH Child Node Sorting for Fast Occlusion Test

Shinji Ogaki, Alexandre Derouet-Jourdan

We show how sorting child nodes of MBVH (Multi Bounding Volume Hierarchy) improves the performance of occlusion test without changing the topology of the data structure. We introduce a cost metric suitable for MBVH which takes into account the distribution of representative rays, and prove that the cost can be minimized by sorting child nodes based on a very simple criterion.
Eurographics Symposium on Rendering (EGSR 2015) - Experimental Ideas & Implementations

EUROGRAPHICS 2014 | STAR – State of The Art Report

Practice and Theory of Blendshape Facial Models

J.P. Lewis, Ken Anjyo, Taehyun Rhee, Mengjie Zhang, Fred Pighin, Zhigang Deng

“Blendshapes”, a simple linear model of facial expression, is the prevalent approach to realistic facial animation. It has driven animated characters in Hollywood films, and is a standard feature of commercial animation packages. The blendshape approach originated in industry, and became a subject of academic research relatively recently. This report describes the published state of the art in this area, covering both literature from the graphics research community, and developments published in industry forums. We show that, despite the simplicity of the blend shape approach, there remain open problems associated with this fundamental technique.
EUROGRAPHICS 2014 State of the Art Reports, pp. 199-218

JGT 2013

Line Selection Tool for 3D Artists

Jaewoo Seo, Ken Anjyo

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 selection tool of a popular image editing software, users can intuitively understand how to use it. A few real-world application examples are also shown, with the user discussions.
Journal of Graphics Tools, Volume 16, Issue 4, pp.233-244

JGT 2012

A Practical Approach to Direct Manipulation Blendshapes

Ken Anjyo, Hideki Todo, J.P. Lewis

This article introduces a few practical and useful techniques to the original work (CGA2010 Paper) and presents the implementation details as a software tool. In addition, this article describes a statistical-prior algorithm that "learns" from previous animation and allows rapid creation of expressive animation in a given style.
Journal of Graphics Tools, Volume 16, Issue 3, 2012, pp. 160-176

Journal of Math-for-Industry (JMI) 2011

RBF interpolation and Gaussian process regression through an RKHS formulation

Ken Anjyo, J. P. Lewis

We describe the formulation of the RBF and Gaussian Process techniques as instances of functional regression in a Reproducing Kernel Hilbert Space. We then show that these techniques can in some cases be reduced to an identical formulation, differing primarily in their assumptions on when the data locations and values are known, as well as in their (respectively) deterministic and stochastic perspectives. The scope and effectiveness of the these techniques are illustrated through several applications in computer graphics.
Journal of Math-for-Industry, Vol. 3 (2011A-6), pp. 63–71, 2011.2

PDF

IEEE CGA 2010

Direct Manipulation Blendshapes

J.P. Lewis, Ken Anjyo

Considering direct manipulation for figure animation has long been possible using inverse kinematics, we propose a similar "inverse kinematics" approach for the popular blendshape facial representation. In both problems the system must infer unknown degrees of freedom during each edit. Our key idea is to solve this inverse problem for faces with a regularizer that minimizes changes in facial expression during editing. The new approach is obvious, easy to implement, and interoperates with traditional blendshape parameter (slider) editing.
IEEE Computer Graphics and Applications Special Issue: Digital Human Faces, Vol. 30(4), p.42-50

PDF MOVIE PROJECT-PAGE

CASA 2009

Stylized Lighting for Cartoon Shader

Hideki Todo, Ken Anjyo, Takeo Igarashi

We propose a 3D stylized lighting method, focusing on several stylized effects including straight lighting, edge lighting, and detail lighting which are important features in hand-drawn cartoon animation. To accomplish these, we introduce a light coordinate system for smooth animation of light and shade. We also extend a toon mapping process for detailed feature lighting.
The Journal of Computer Animation and Virtual World (CASA 2009), Vol. 20, issue 2-3, pp.143-152

MOVIE

CASA 2009

N-way Morphing for 2D Animation

N-way morphing for 2D animation

William Baxter, Pascal Barla, Ken Anjyo

We present a novel approach to the creation of varied animations by interpolating a small set of input images in a reduced pose-space. The technique includes an N-way mapping technique, an efficient, rigidity preserving nonlinear blending function, improved extrapolation and a novel scattered data interpolation technique to manage the reduced pose-space. Together these allow users to intuitively and interactively control temporal behaviours with simple gestures.
The Journal of Computer Animation and Virtual World (CASA 2009), Vol. 20, issue 2-3, pp. 79-87

TVCG 2009 | Technical Report OLMTRE-2008-001

Compatible Embedding for 2D Shape Animation

William Baxter, Pascal Barla, Ken Anjyo

We present new algorithms for the compatible embedding of 2D shapes. Such embeddings offer a convenient way to interpolate shapes having complex, detailed features. Compared to existing techniques, our approach requires less user input, and is faster, more robust, and simpler to implement, making it ideal for interactive use in practical applications. Our algorithms allows us to demonstrate 2D shape interpolation with instant feedback. The proposed algorithms exhibit a combination of simplicity, speed, and accuracy that has not been achieved in previous work.
Visualization and Computer Graphics, IEEE Transactions, Vol.15 , Issue 5, pp. 867-879

PDF

EUROGRAPHICS 2009

Animating Pictures of Fluid using Video Examples

Makoto Okabe, Ken Anjyo, Takeo Igarashi, Hans-Peter Seidel

We propose a system that allows the user to design a continuous flow animation starting from a still fluid image. The basic idea is to apply the fluid motion extracted from a video example to the target image. We designed animations of various pictures, such as rivers, waterfalls, fires, and smoke. The upper example animates a campfire in our artist’s painting using a fire video. The bottom example animates a water surface in Johannes Vermeer’s painting using an ocean video.
Computer Graphics Forum (EUROGRAPHICS 2009 Special Issue), vol.28. No.2, pp.677-686

MOVIE PROJECT-PAGE

CASA 2008

Directable Animation of Elastic Bodies with Point-Constraints

Ryo Kondo, Ken Anjyo

We propose a simple framework for making elastic body animation with point constraints. Our algorithms provide animators a practical way to make elastic body animation with plausible realism, while effectively using point-constraints to offer directatorial control. The animation examples illustrate that our framework creates a wide variety of point-constraint animations of elastic objects with greater directability than existing methods.
The Journal of Computer Animation and Virtual World (CASA 2008), Vol. 19, Issue 3-4, pp.165-173

MOVIE

NPAR 2008

Rigid Shape Interpolation Using Normal Equations

William Baxter, Pascal Barla, Ken Anjyo

We provide a new compact formulation of rigid shape interpolation in terms of normal equations, and propose several enhancements to previous techniques.
Proc. The 6th International Symposium on Non-Photorealistic Animation and Rendering (NPAR 2008), pp.59-64

Detail

SIGGRAPH 2007

Locally Controllable Stylized Shading

Hideki Todo, Ken Anjyo, William Baxter, Takeo Igarashi

We propose a set of simple stylized shading algorithms that allow the user to freely add localized light and shade to a model in a manner that is consistent and seamlessly integrated with conventional lighting techniques. The algorithms provide an intuitive, direct manipulation method based on a paint-brush metaphor, to control and edit the light and shade locally as desired.
ACM Transactions on Graphics (SIGGRAPH2007) Vol. 26, Issue 3, Article No.17

Detail PDF

EUROGRAPHICS 2006

Latent Doodle Space

William Baxter, Ken Anjyo

We propose the concept of a latent doodle space, a low-dimensional space derived from a set of input doodles, or simple line drawings. The latent space provides a foundation for generating new drawings that are similar, but not identical to, the input examples. We present two practical applications that demonstrate the utility of this idea: first, a randomized stamp tool that creates a different image on every usage; and second, “personalized probabilistic fonts,” a handwriting synthesis technique that mimics the idiosyncrasies of one’s own handwriting.
Computer Graphics Forum (Eurographics2006), Vol.25(3), pp.477-485,

NPAR 2006

Tweakable Light and Shade for Cartoon Animation

Ken Anjyo, Shuhei Wemler, William Baxter

We propose an intuitive, direct manipulation method for animating stylized light and shade in real-time. Our method provides intuitive click-and-drag operations for translating and deforming the shaded areas, including rotation, directional scaling, splitting, and squaring of highlights, all without tedious parameter tuning.
Proc. of NPAR 2006, The 4th International Symposium on Non-Photorealistic Animation and Rendering, pp.133-139

SCA 2005

Directable Animation of Elastic Objects

Ryo Kondo, Takashi Kanai, Ken Anjyo

There is a crucial demand in the computer animation industry to make animations that blend animator-specified expressive motion with physics-based realism. We propose a novel framework to create directable animation of elastically deformable objects. The directable animation is created with animator-specified keyframes and the motion trajectory of the deformable object, while maintaining a plausible realism.
Proc. ACM SIGGRAPH/ Eurographics Symposium on Computer Animation (SCA2005), pp.127-134

IEEE CGA 2003

Stylized Highlights for Cartoon Rendering and Animation

Ken Anjyo, Katsuaki Hiramitsu

This article presents an approach that generalizes the concept of a highlight for 3D objects in cel animation. This highlight shader enables cartoon-style highlighting through simple operations defined for the highlight vector field. These operations actually correspond to the direct manipulations on the highlight area defined by the vector field, these include local affine transform and simple deformation of the highlight.
IEEE Computer Graphics and Applications Vol.23 No. 4 (Special issue on Non-Photorealistic Rendering) pp.54-61

Detail MOVIE

Notes

Technical Report OLMTRE-2008-002

Notes on Compatible 2D Shape Embedding

William Baxter, Pascal Barla, Ken Anjyo

Technical Note (in Japanese) OLMNOTE-2004-001

Highlight Shader

Ken Anjyo