Reiji Tsuruno

Three-dimensional deformation and stress distribution in an analytical/computational model of the anterior cruciate ligament

In this study, a constitutive equation for the ACL composite was formulated, and 3-D finite deformations and stress distributions of the ACL were calculated using a finite element method to simulate knee flexion. The mathematical model of the ACL was created by a structurally motivated phenomenological approach. It was assumed that the ACL can be ideally represented as a homogeneous hyperelastic matrix (Mooney-Rivin material) in which two families of densely distributed extensible fibers are embedded; the fibers in one family have a parallel orientation, the other fibers extend radially in eight equally spaced directions. The non-linear stress-strain characteristic exhibited by collagen fibers was represented by a tri-linear curve. Simulation was performed and the results provided some original data; the stress distribution within the ACL body as well as that over the surface, the 3-D deformations and stress distributions of the ACL viewed from other sides in addition to those from the medial side, and the variations of the stress distribution pattern in the ACL which occurred when the tibia was displaced anteriorly or posteriorly.

Preserving Fluid Sheets with Adaptively Sampled Anisotropic Particles

This paper presents a particle-based model for preserving fluid sheets of animated liquids with an adaptively sampled Fluid-Implicit-Particle (FLIP) method. In our method, we preserve fluid sheets by filling the breaking sheets with particle splitting in the thin regions, and by collapsing them in the deep water. To identify the critically thin parts, we compute the anisotropy of the particle neighborhoods, and use this information as a resampling criterion to reconstruct thin liquid surfaces. Unlike previous approaches, our method does not suffer from diffusive surfaces or complex remeshing operations, and robustly handles topology changes with the use of a meshless representation. We extend the underlying FLIP model with an anisotropic position correction to improve the particle spacing, and adaptive sampling to efficiently perform simulations of larger volumes. Due to the Lagrangian nature of our method, it can be easily implemented and efficiently parallelized. The results show that our method can produce visually complex liquid animations with thin structures and vivid motions.

A particle-based method for preserving fluid sheets

We present a new particle-based method that explicitly preserves thin fluid sheets for animating liquids. Our primary contribution is a meshless particle-based framework that splits at thin points and collapses at dense points to prevent the breakup of liquid. In contrast to existing surface tracking methods, the proposed framework does not suffer from numerical diffusion or tangles, and robustly handles topology changes by the meshless representation. As the underlying fluid model, we use Fluid-Implicit-Particle (FLIP) with weak spring forces to generate smooth particle-based liquid animation that maintains an even spatial particle distribution in the presence of eddying or inertial motions. The thin features are detected by examining stretches of distributions of neighboring particles by performing Principle Component Analysis (PCA), which is used to reconstruct thin surfaces with anisotropic kernels. Our algorithm is intuitively implemented, easy to parallelize and capable of producing visually complex thin liquid animations.

Extended papers from NPAR 2010: Vector graphics depicting marbling flow

We present an efficient framework for generating marbled textures that can be exported into a vector graphics format based on an explicit surface tracking method. The proposed method enables artists to create complex and realistic marbling textures that can be used for design purposes. Our algorithm is unique in that the marbling paint on the surface of water is represented as an enclosed contour and is advected by fluid flow to deform the marbling silhouette. In contrast to previous methods, in which the shape is tracked with a concentration density field in Eulerian grids, our approach facilitates greater complexity that is free from grid resolution and per-pixel computation while retaining real-time performance. To forestall the propagation of large vertices, we adaptively resample the contours, exploiting the curvature and the turbulence of the fluid as criteria. At the convection phase, we parallelly advect contour particles on a Graphics Processing Unit (GPU) in addition to applying volume corrections. Finally, we quickly remove extremely thin lines in shapes to remove dozens of vertices. We performed our method with an interactive prototype to demonstrate the robustness of the proposed method in several scenarios.

P3-factorization of complete multipartite graphs

In this paper, it is shown that a necessary and sufficient condition for the existence of aP3-factorization ofKmn is (i)mn ≡ 0(mod 3) and (ii) (m − 1)n ≡ 0(mod 4).

Visualization of Dyeing based on Diffusion and Adsorption Theories

This paper describes a method for simulating and visualizing dyeing based on weave patterns and the physical parameters of the threads and the dye. We apply Ficks second law with a variable diffusion coefficient. We calculate the diffusion coefficient using the porosity, tortuosity, and the dye concentration based on the physical chemistry of dyeing. The tortuosity of the channel was incorporated in order to consider the effect of the weave patterns on diffusion. In this model, the total mass is conserved. We describe the cloth model using a two-layered cellular model that includes the essential factors required for representing the weft and warp. Our model also includes a simple dyeing technique that produces dyeing patterns by interrupting the diffusion of the dye in a cloth using a press. The results obtained using our model demonstrate that it is capable of modeling many of the characteristics of dyeing.In geometric computing, a shape is typically viewed as a set of points and then represented accordingly, depending on the available data and the application. However, it has been known for a long time that simple shapes may be treated more elegantly by viewing them as points in a higher-dimensional space. Examples include line and sphere geometries, kinematical geometry and Lie groups. Recently, fundamental mathematical properties of spaces of more complicated objects have been studied and applied to certain problems in image processing.

Segmental Brush Synthesis with Stroke Images

We present a new approach for synthesizing realistic brush strokes exploiting recent works of texture synthesis from stroke images. (See Figure 1). In our method, stroke images are automatically decomposed into a sequence of quad segments and stitched together along the path of user’s input to produce final image. Numbers of methods using textures on digital painting have been explored; our usage of texture is novel in that the source image is typically a photo and the synthesis is fast enough to achieve realtime feedback. In contrast to previous methods, our approach allows a large variety of artistic brushes to be interactively simulated fairly so that unique media which haven’t caught attention yet such as lipsticks or finger paint, are well reproduced. We shall show some artworks created using our method and demonstrate feasibility of our algorithm.

Natural-looking strokes for drawing applications

This paper presents an algorithm for generating realistic drawing strokes in real-time that can take on the appearance of pastels, charcoals, or crayons. The similarity between the pigment deposit patterns on paper surfaces produced by pastel strokes and the shadows/shades on illuminated paper surfaces have been investigated. Multiple paper textures have been prepared and the paper surfaces have been ascertained by illumination from various directions to represent strokes in arbitrary directions. These textures have been processed as if they could be used as a height field, and pigments deposited on the paper have been calculated using the height field and tablet inputs.

Video game that uses skin contact as controller input

In this paper, we present the first stage of our video game prototype which treats skin contact as controller input. Skin contact is communication which has special emotion. Video game also has elements of communication, for instance, Family Computer [Nintendo 1983] has two controllers in order that family or friends can play the game together. We use these two features and propose the interaction that players can enjoy video games with skin contact. We implemented the game controller and two video games. The controller has the mechanism which enables to detect skin contact. One of games of our prototype is a shoot-em-up game. Another is a rhythm action game. Our goal of this research is to show the increase of enjoyment and intimacy at the game with using skin contact.

Pastel-like rendering considering the properties of pigments and support medium

There has been any works specifically on computer generated 3D pastel rendering. Some rendering or imaging softwares can generate pastel drawing-like images recently, but most of them cannot modeling and rendering objects as 3D, and do not have enough power of expression in comparison with real-pastel drawings.