• Technical Survey
     

    Visual Simulation of Natural Scenery
    Norishige Chiba
    Abstract: 
    In this paper, we first outline the CG technologies studied so far for visually simulating natural scenery. Then, we will show our related research results with several CG images of virtual nature.


  • The Practical Application Times of the CG Technology for Visually Simulating Natural Phenomena
    Norishige Chiba


    CG Simulation of Natural Objects and Phenomena
     Norishige Chiba


    Introduction to 3 Dimensional Computer Graphics(7): CG
     Simulation of Natural Objects and Its Applications
     Norishige Chiba
     



     
  • Visual Simulation of Trees
  •  

    An Integrated Growth Model of a Botanical Tree for CG Taking into Account the Interaction between the Root and the Ground Part
     Ken Ohshida , Kazunobu Muraoka and Norishige Chiba

    Abstract: (Japanese)
    Modeling technique of botanical trees for Computer Graphics (CG), especially development of the growth model is one of the fields that have most actively been studied. However, there have been quite a few reports so far made on the growth model of the root, the subsurface part of a tree and there have been no proposal so far made on the growth model incorporating the interaction between the subsurface part and the ground part. A root is an organ to fix the plant body with reference to the ground and absorb the subsurface nourishing water, hence not only closely related to the growth of the ground part but also exerts great influences over the shape of a tree. In this paper, we first propose the growth model of the root and next present the growth model in which this "subsurface part" of this growth model is linked with the previously proposed "ground part" of the tree, in other words, the integrated growth model incorporating the interaction between ground part and subsurface part. This integrated growth model of a tree has possible applications to the amusement systems based on computer simulation, such as bonsai (miniature potted trees) , gardening and landscape design presentation support systems and education support systems.



    A Growth Model Having the Abilities of
      Growth-Regulations for Simulating
       Visual Nature of Botanical Trees
    Norishige Chiba, Ken Ohshida, Kazunobu Muraoka, Mamoru Miura and Nobuji Saito

    Abstract:
     Although the representation methods of botanical trees have been presented by several researchers in recent years, simulating natural tree features acquired in a growth process still remains a challenging problem. Since tree shape is significantly influenced by its growth environment, such as sunlight conditions and random "accidental" pruning of branches (e.g., caused by storm or a gardener), not only does no tree have a regular shape, but no two trees are identical, even if they are of the same species. In previous papers we have shown an attractive fact that if we take into account the abilities of several growth regulations such as heliotropism and dormancy break, we can easily simulate realistic irregular branching patterns.  In this paper, we will present the improved growth model taking into account the following growth regulations: (a) withering, (b) heliotropism, (c) geotropism, and (d) apical dominance: (d-1 ) suppression to lateral shoots, (d-2) dormancy break, and (d-3 ) change in leadership. These growth regulations are implemented by employing an "imaginary plant hormone" for implementing the ability of the communication between all buds and branches of a tree. This means that any "central control unit" that keeps watch on he condition of the whole tree and issues commands for each bud and branch to control the growth is unnecessary for a tree. This point is one of the interesting features of our growth model.


    Image Generation Method for Swaying Branches by Wind
    Norishige Chibe , Mitsuru Kono, Yoshito Sato, Kazunobu Muraoka and Nobuji Saito.

    Abstract:(Japanese)
    Several attempts to produce CG images of botanical trees have been made in a wide range of areas form science on from to art. Some of the authors have been trying to develop a growth model of trees for producing a realistic shape of a tree which plays a vital role in the CG simulations of natural sceneries required for various applications, such as environmental assessment for large construction projects, flight simulations, driving simulations, and special effects in films. From the viewpoints of these applications, an efficient motion simulation method of branches and leaves swaying in the wind is required as well as that of the shape of a tree.  In this paper, we present a simple simulation method of the motion of branches swaying in the wind. The method employs a tree structure model whose adjacent nodes (i. e. particles) are loosely coupled and change their positions according to individual motion equations. In the model, discretization errors produced by Euler's method are approximately solved by restitutive force which is introduced so as to maintain the stable relative positions of nodes. Our method has merits that it is efficient and is easy to understand.


    A Growth Model of Botanical Trees  Generation of Natural
      Shapes of Trees Based on an Imaginary Plant Hormone
     Norishige Chiba, Shunichi Ohkawa,   Kazunobu Muraoka and Mamoru Miura

    Abstract:(Japanese)


    CG Simulation of Natural Shapes of Botanical Trees Based on Heliotropism
    Naoyoshi Kanamaru , Norishige Chiba,  Kiyoaki Takahashi, Nonmember and Nobuji Saito

    Abstract:(Japanese)



     
  • Visual Simulation of Autumn Colors


  • Image Generation Method for Seasonal Mountain Scenery
    Kazunobu Muraoka , Norishige Chiba , Tadashi Takahashi  and Nobuji Saito

    Abstract:(Japanese)
    Realistic image synthesis of mountain scenery plays a vital role in the visual simulation of landscape carried out in many areas, such as in the environmental assessment for construction projects and in special effects in films. It is especially interesting and important to develop CG techniques for simulating pleasant visual impressions of seasonal mountain scenery. In this paper, we present a fundamental idea to construct the following skeletal methods for simulating seasonal colors of a forest corresponding to natural phenomenon, such as fresh verdure, autumn leaves, fallen leaves, and snow fall : ( 1 ) a method for determining a vegetation map suitable for a given point, represented by latitude and altitude, and a given topography, ( 2 ) a method for generating desirable color sequences according to the types of trees, and ( 3 ) a CG image generation method based on 3D geometrical models of trees. Finally, we demonstrate the advantage of our idea by showing CG images of simulated mountain sceneries in the four seasons.


     A Fast Algorithm for Determining the lnsolation
           at the Surface of the Earth
     Norishige Chiba  and Kazuhito Yaegashi

    Abstract:(Japanese)
    A digital terrain model is a two-dimensional array which contains elevations of the surface of the Earth. The elevation data are sampled at regular mesh points of appropriate resolution. This paper presents a fast algorithm for determining the isolation on the surface patches at each mesh point. In the case where it can be assumed that it is sufficient to consider only direct rays from a single light source, the insolation at a point in time can easily be computed by employing a hidden surface elimination algorithm having the viewpoint at the light source. In general, however, at the point where the insolation must be determined considering scattered light integrated over an interested period, it is necessary to execute the hidden surface eliminations applied in every direction from the  celestial sphere. The algorithm herein has a time complexity of O( [square root of] mn2). This is smaller than those of O(mn2) of naive algorithms employing hidden surface eliminations applied in m directions, where the resolution of digital terrain is n x n. An implemented program shows that our algorithm is 33 times faster than the naive one for m [neary equals] 8 100 and 67 times for m [neary equals] 32,400.



     
  • Visual Simulation of Eroded Terrain


  • Terrain Simulation Based on the Recursive Refinement of Redge-Lines
    N.Chiba, K.Muraoka, K.Yaegashi and M.Miura

    Abstract:
    Since CG Simulation of natural terrain has applications in many areas, various modeling methods of terrain including imaginary forgeries have been developed. In this paper, we present a new approach which is suitable for modeling such imaginary mountains produced by erosion processes. Such terrain can not be simulated by standard fractal surfaces. Our algorithm synthesizes the forgery of natural mountain by refining the given initial ridge-lines which reflect the outline of the ideal forgery. The refinement is established by adding derivative ridge-lines recursively to those produced so far. Although we can recognize ridge-lines as a notable geographical feature of mountains produced especially by erosion processes, no such modeling method has been designed so far.


    Interpolation for Digital Terrain Modeling
    Norishige Chiba, Kazunobu Muraoka, Masakazu Misawa and Nobuji Saito

    Abstract:(Japanese)


    Simulation of Natural Scenes
    - Modeling for Mountains -
    Kazunobu Muraoka, Norishige Chiba and Nobuji Saito

    Abstract:(Japanese)


    Modeling of Rock Form Taking into Account Growing Process of Columnar Joints
    Tomoya Ito, Tadahiro Fujimoto and Norishige Chiba

    Abstract:(Japanese)
    In the present paper, we propose a rock form modeling method based on the simulation of the growing process of columnar joints. Joint form is an important factor in modeling which provides the visual feature of rocky scenery. However, there have been few reports on methods for generating rocky scenery taking into account the joint form. The proposed method consists of the following steps: (1) determining the temperature distribution in the given initial lava volume by via heat conduction simulation, (2) determining the contraction center curved lines according to the temperature distribution, (3) defining a three-dimensional Voronoi region corresponding to each of the contraction center curved lines, and (4) simulating weathering phenomena. For efficiency of computation, we use a voxel space of low-resolution for (1) and a voxel space of  high-resolution for (2)-(4). Using this method, we can easily produce various types of columnar joint form by specifying the appropriate boundary conditions.

     



     
  • Visual Simulation of Flames
  •  

    Particle-Based Visual Simulation of Explosive Flames

    Daiki.Takeshita, Sin Ota, Machiko Tamura, Tadahiro Fujimoto, Kazunobu Muraoka, Norishige Chiba

    Abstract:
    In the present paper, we propose a particle-based method for the visual simulation of explosive flames. This method consists of a numerical simulation method based on a fluid model described by discrete Lagrangian using particles and a rendering method for generating a CG animation from the movement data of the particles. This fluid model uses flame particles and air particles. The model calculates the buoyancy caused by the difference in temperature as the external force in the Navier-Stokes equations and approximates the viscous force and pressure via a discrete particle model. In addition, the heat conduction between particles and the heat radiation is taken into account. The proposed method realizes the representation of distinctive phenomena such as an ascending airflow with a quantity of explosive flame and a swirling airflow behind the ascending airflow. CG images are rendered using a Z-buffer based volume rendering method.

     
     


    Image Synthesis of Frickering Scenes Including Simulated FIames
    Jun-ya Takahashi, Hiromichi Takahashi and Norishige Chiba

    Abstract:
    Producing realistic images and animations of flames is one of the most interesting subjects in the field of computer graphics. In a recent paper, we described a two-dimensional particle-based visual method of simulating flames. In the present paper, we first extend the simulation method, without losing any of its desirable features, in such a way that it functions in three-dimensional space. We then present an efficient method of producing an image of the scene, including flames acting as volume light sources, which normally requires a large amount of computing time in the usual simulation approaches. Finally, we demonstrate the capabilities of our visual simulation method by showing sample images generated by it, which are excerpted from an animation.


    Visual Simulation of Flames, Proceedings of CAD / VSMM'95 in Gifu
    J.Takahashi, H.Takahashi and N.Chiba

    Abstract:
    Producing realistic images and animations of flames is one of the most interesting subjects in CG field. Recently Cwe have presented a two-dimensional particle-based visual simulation method for flames. In this paper, Cwe first extend the simulation method without losing any of desirable abilities so that it works in three-dimensional space. Then, we present an efficient rendering method for producing an image of the scene including flames acting as volume light sources which require a large amount of computational time in general rendering approaches. We finauy demonstrate the ability of our visual simulation method by showing the generated images which are excerpts from an animation.


    Two-dimensional Visual Simulation of  Flames, Smoke and the Spread of Fire
     Norishige Chiba, Kazunobu Muraoka, Hiromichi Takahashi and Mamoru Miura

    Abstract:
    Since CG simulation of natural phenomena on the basis of their forms and motions has many applications, such as various landscape designs and special effects in films, it is very important and interesting to develop efficient techniques for their visual simulation. It is especially interesting to produce realistic images and animations of flames and smoke, on account of their complicated patterns of behavior. Effective simulation methods for names and smoke are expected to satisfy the following requirements:
    1. The motion of flames or smoke produced in an interaction with obstacles can be simulated.
    2. The motion of flames and smoke can be easily controlled according to scenarios.
    3. The spread of fire can be simulated. Although several useful representation methods have been proposed so far, simulating flames and smoke still remains a challenging problem. In this paper, we first describe our basic two-dimensional visual simulation method based on particle-based simulation, but not based on exact physical simulation. Roughly speaking, our method assumes that the images of flames and smoke arc basically obtained by visualizing turbulence, that is, the particles of flames and smoke play the role of tracers in the field of turbulence. Next, we present an improved method for simulating the spread of fire and the appearance of smoke produced in an incomplete combustion. Simultaneously, we show several examples of the simulation. Finally, we will touch slightly on further problems for extending the model to one which works in three-dimensional space.


    2D CG Simulation of Smoke and Flames Using Vortex Fields
     and Particles
    Kazunobu Muraoka , Norishige Chiba, Hiromichi Takahashi and Mamoru Miura

    Abstract:(Japanese)



     
  • Visual Simulation of Water Currents


  • Visual Simulation of Water Currents Using a
       Particle-based Behavioral Model
    Norishige Chiba, Shinji Sanakanishi, Kenichiro Yokoyama, Isao Ootawara, Kazunobu Muraoka and Nobuji Saito

    Abstract:
    Several CG researchers have Simulated impressive ocean waves so, far. Recently, other researchers have succeeded in simulating waterfalls by employing a mass of particles. However, visual simulation of water currents having complex surfaces, such as mountain streams and turbulent water, still remains a challenging problem thanks to their complicated patterns of behavior. Effective simulation methods for water currents arc expected to have abilities to represent the following remarkable behavioral visual features of water: the appearance of a pool, an obstacle avoidance now, a fluent flow, a now into an open space, the collision and the confluence of flows and the occurrence of splashes.  In this paper, we present a new type of particle-based simulation method for complex water currents which is not based on strict fluid dynamics but rather classified into a "quasi-physically-based' simulation method constructed on the basis of algorithmic approaches. We first present a simple behavioral model of a "water-particle". Next, we propose a method for generating CG images of water currents from a set of water-particles. Finally, we demonstrate the ability of our method by showing several examples of the simulation.



     
  • Visual Simulation of Snow


  • A Visual Simulation of Melting Snow
    Kazunobu Muraoka and Norishige Chiba

    Abstract:(Japanese)
    Generating natural scenery using computer graphics is a fundamental technology for the production of visual contents. Especially, the generation of natural seasonal scenes is an attractive theme including many difficult problems to solve. To aid in the generation of snow images that are essential to natural winter scenes, this paper proposes a method for simulating snow accumulation and melting. Snow coverage undergoes a complex set of changes not only during snowfall but also during melting. Many factors, such as sunlight, ground heat, and radiant heat from surrounding objects affect snow melting. By using these factors to simulate thermal conduction, the proposed technique automatically generates an image of melting snow from snow coverage data defined as volume data. This paper also proposes an image generation method based on volume rendering and presents several example images generated using this method.


    Snowfall Model for Simulating Close View of Snowy Landscape
    Kazunobu Muraoka, Norishige Chiba and Isao Ootawara

    Abstract:(Japanese)
    Visual simulation of seasonal mountain scenery plays a vital role in the realistic image  synthesis of natural scenery. In this paper, we will present a snowfall model to simulate a close view of a  snowy landscape including snowcapped garden stones or stone lanterns. Using this model, we can produce  typical accumulations of snow by specifying a few parameters for the model.



     
  • Visual Simulation of Clouds


  • Visual Simulation of Cumulus Types of Cloud
    Tsukasa Kikuchi, Kazunobu Muraoka and Norishige Chiba

    Abstract:(Japanese)
    In the previous paper, we have proposed the visual simulation method for generating the realistic animations of the growth of cumulonimbus clouds. In the method, assuming a cloud to be a cluster of globe-shaped cloud primitives, moreover each cloud primitive to be represented by a single particle (cloud particle) , we have given the qualitative model for simulating updrafts and freezing of vapor. Mapping 3D texture of a globe-shaped cloud primitive to the motion data of cloud particles given by the updraft simulation based on the qualitative model, and rendering the 3D textures by taking into account only the single scattering, we can make the animation of growth processes of cumulonimbus clouds.  This paper first proposes an acceleration technique for the 3D texture rendering algorithm, and then present visual simulation techniques of cumulus types of cloud constructed by extending the previously proposed techniques. These techniques enable us to generate the animations of drifting clouds with changing their status, i.e., appearance, growing and disappearance.


    Visual Simulation of Cumulonoimbus of Clouds
    Tsukasa Kikuchi, Kazunobu Muraoka and Norishige Chiba

    Abstract:(Japanese)
    Computer graphics(CG) is a key technology for producing visual contents. Currently, computer generated imagery(CGI) techniques are being developed and applied, particularly in the field of film production, to provide total composition of real images and CG images. Therefore, the development of CG technologies that are capable of realistically displaying a variety of objects and phenomena that exist in the natural world is becoming increasingly important.
     This paper proposes a three-dimensional CG technique for generating cloud images. The proposed technique regards a cloud as a group of cloud masses, each of which is represented by a single particle (cloud particle) for the visual simulation of clouds. This technique consists of a modeling process and a rending process. The modeling process moves each particle according to buoyancy, the force of interaction between particles, and the repulsive force the particle receives from the atmosphere. The buoyancy is dependent on the relationship between temperature, atmospheric pressure, and air density. The rendering. process takes into account only the single scattering using a phase function. The function is coupled from isotropic scattering, Mie scattering, Rayleigh scattering in the volume data defined by the cloud particles.



     
  • Visual Simulation of Aging Process

  •  

    Modeling of Wood Aging Caused by Biological Deterioration
    Xing Yin, Tadahiro Fujimoto, Norishige Chiba, and Hiromi T.Tanaka

    Abstract:
     We propose visually simulating wood aging by microorganisms using an ant colony optimization algorithm to generate wood aging patterns. Ants deposit pheromone similar to termites and wood deterioration caused by termites is simulated using this algorithm. Patterns generated by this algorithm resemble many pattern in nature, meaning ant paths are representative of worm paths and ant pheromones are representative of microorganism growth. We demonstrate the effectiveness of this technique in experiments.

     
     


    CG Representation of Wood Aging with Distortion, Cracking and Erosion
    Xing Yin, Tadahiro Fujimoto and Norishige Chiba

    Abstract:
     Materials exposed to the elements change in appearance because of aging. Because wood is an organic substance, cracks and the surface erosion occur easily. To produce realistic computer graphic images, we need simulate the aging phenomenon also. Here, we propose a visual simulation of the distortion, cracking, and erosion of wood. In this method, wood is represented by a tetrahedral mesh. By setting semi-physical variables at each vertex in  this mesh, a visual simulation of wood aging can be accomplished. The surface of the wood is defined by values assigned to the superficial tetrahedral mesh vertices. Changes in the surface are achieved by value changes. The effectiveness of this method is demonstrated by applications on a plank and shapes such as a bunny and an armadillo statue.

     
     


     

    Painting Canvas Synthesis
    Frederic Drago and Norishige Chiba

    Abstract:  
     We present the development of a procedural method for texturing and modeling different kinds of woven canvas used to support easel paintings. The detailed macro- and microgeometry of textiles and different weaving patterns found in woven fabrics is conveniently simulated by procedural displacement and surface shading. The common varieties of canvas used in art production since the Italian Renaissance period are presented and recreated. The anatomy of an oil-based painting is briefly introduced and a visual simulation of decay presented. We also apply our texturing and shading techniques to a simple geometric representation of painting to help visualize the changing characteristics developed during the aging process of a canvas support kept in uncontrolled environmental conditions.

     



     
    Visual Simulation of Moss Taking into Account Growth Environment
    Yuuji.Ogasawara, Kazunobu Muraoka, Norishige Chiba

    Abstract: (Japanese)
    The CG technology for realistically representing the various things and phenomena that constitute natural scenery is becoming an increasingly important theme. The image generation of moss is also a very interesting theme from the viewpoint of visual simulation of both the natural texture and secular change of the ground and stonework, e.g.garden lanterns, stepping stones, paving stones and stone walls. In this paper, we propose a method for simulating the growth of moss qualitatively that takes into account several factors of the growth environment, such as amount of sunlight, temperature, humidity, and soil.
    Key words: Computer Graphics, Natural Phenomena, Plants, Moss, Growth Model.

     


    Visual Simulation of Wood Weathering
    Xin Yin, Tadahiro Fujimoto, Kazunobu Muraoka, Norishige Chiba

    Abstract: (Japanese)
    The aging process of material is an unavoidable natural phenomenon. Thus, several CG techniques for representing aging phenomena, such as metal corrosion and stone weathering, have been studied. In this paper, we propose a visual simulation method of wood weathering. First, we present the wood model in consideration of branching. Then, we give the algorithm for representing the weathering of the color and shape of wood. Several simulation examples show the availability of the proposed method. Finally, we conclude this paper and mention the future work. Keywords: wood, weathering, erosion, visual simulation, modeling, solid texture.


    Visual Simulation of Moss Taking into Account Local Environment on Temperature and Humidity

    Yuuji.Ogasawara, Kazunobu Muraoka, Norishige Chiba

    Abstract: (Japanese)
    The CG technology for more realistically representing the natural scenery is becoming an increasingly important theme. Moss is one of the essential components of Japanese gardens. Most people may be impressed with the Japanese garden whose ground and stonework, e.g. garden lanterns, are tastefully covered by moss. In this paper, We propose the method to take into account the environmental features for the growth simulation of moss by mainly simulating the wind flow. Those features include the waterside, the ground shape and other components, shapes. In our proposed method, the local distribution of temperature, humidity and wind velocity inAuenced by the environmental features are estimated by employing the particle-based wind flow simulation, and used for the growth simulation of moss.


     

  • Multi-resolution CG -3D Textur and LOD-


  • An Anisotropic Three-dimensional Texture Method
    Kazunobu Muraoka and Norishige Chiba

    Abstract: (Japanese)
    Three-dimensional textures are suitable for generating aliasing-free images of objects having fine surface structure. The"texel"is a typical three-dimensional texture. Each element of the three-dimensional texture includes rendering-parameters, e. g., reflection distribution and object density. In previous works, although these parameters are anisotropic, most of them except reflection distribution  are often assumed as just scalars for the sake of simplicity. In this paper, we present the modeling method for transforming a given poligon-based geometric model into the  anisotropic three-dimensional texture, and the rendering method for generating aliasing-free images from the texture.


    Rendering of Forest Scenery Using 3D Textures
      Norishige Chiba, Kazunobu Muraoka, Aki Doi and Junya Hosokawa

    Abstract:
    Visual simulation of forest scenery is a challenging problem which includes the following tough sub-problems: generation of vegetation, representation of trees, simulation of color change of leaves and rendering of numerous trees. Among those sub-problems, this paper treats mainly the last one. A conventional polygon-based rendering algorithm often produces troublesome aliasing effects when it is applied to the objects having complex fine surfaces, such as forest scenery. In this paper, we show that an extended volume rendering technique applied to 3D textures, i.e.volume data in this paper, of trees is effective in the concerned problem. Kajiya left, as further work, the problem of rendering forest scenery by applying his 3D texture called texel. Our rendering method consists of the following three steps: we first generate 3D textures of trees from their polygon-based geometric models, we next arrange the 3D textures, allowing their possible mutual intersections, on the surface of a given polygon-based terrain model according to a simulated vegetation, and we finally produce an image of forest scenery by applying the raytracing algorithm including our slightly extended volume rendering technique. @ 1997 by John Wiley & Sons, Ltd.


      An Efficient Texel Generation Method
    Kazunobu Muraoka, Naoko Kikuchi, Norishige Chiba and Isao Ohtawara

    Abstract:(Japanese)



     
  • Volume Rendering


  •  Fast Interpolation Algorithms Using FFT
    Norishige Chiba, Keimei Kaino and  Mamoru Miura

    Abstract:(Japanese)


    A Fast DDA Algorithm for Finding All the Raster Elements through Which
     the Given Continuous Line Segment Runs
    Kenichiro Yokoyama, Norishige Chiba and Norio Tayama


      A Voxel Based Geometric Modering
    Norishige Chiba, Tomio Aoki and Nobuji Saito

    Abstract:(Japanese)



     
  • Visual Simulation of Ceramic Art 


  • Crack pattern simulation based on 3D surface cellular automata
     Stepane Gobron, Norishige Chiba

    Abstract:
    This article describes a method for modeling the propagation of cracks on any 3D surface. This method allows almost any type of cracks on any type of triangulated 3D Object Our model's main advantage is that it proposes a semi-physical solution
    , making it both user controllable and easily extensible. We first introduce the general development of cracks. We then present our original model of spectrum stress, followed by a description of the mutual interaction between cracks and stresses. Then, We describe special rendering techniques including the multi-thickness anti-aliasing linked segment method and the crack mirror special effect. The final section presents intermediate graphical results that review the entire model as well as a set of different crack patterns using various types of material such as concrete, ceramic, mud, and glaze.
     


    Particle-based Visual Simulation of Virtual Clay
     Yasuyuki Oda, Kazunobu Muraoka, Norishige Chiba

    Abstract:
     In the shape modeling of deformable objects for Computer Graphics or Virtual Reality, if the intuitive physical modification operations as those used in real clay craft, e.g., simple modification operations like pressing, bending and extending, are possible, "virtual clay craft" would be realizable. Such a realistic shape modeling technique has many applications in the areas of education, art, amusement, virtual reality, and so on.
      In this paper, we propose a clay model implemented by employing the particle based numerical simulation method where every pair of particles receives specific virtual mutual forces each other. These virtual forces consist of gravity, attractive force, repulsive force, friction force and external force that realize clay-like deformation of objects. Actual clay has the property of plasticity where its shape remains as it was after the external forces are removed. Our clay model realizes not only the fundamental modification operations applied to clay but also the plasticity.
     
     


    A Behavioral Model of Cracks and Its Applications to CG
     Norishige Chiba, Seiichi Wada and Keimei Kaino and Kazunobu Muraoka

    Abstract:(Japanese)
     Cracks produced by drying mud-like naterials exhibit various patterns of form (including the crack patterns that occur on plate glass and on the ground) according to the stickiness of the materials. It is very interesting and important to develop a behavioral model of cracks.  which produces realistic crack patterns. from not only a theoretical but a practical view, e.g.,realistic image synthesis in CG.
      In this paper, we first analyze the typical two crack patterns produced in different materials, one of which is only slightly sticky and the other is very sticky. We then show some basic assumptions useful for constructing a behavioral model of cracks.
     Next, we present the behavioral modal having one parameter of stickiness; and presenting several simulated crack patterns, we show that the constructed model is effective for visual simulation of crack patterns.
      We then present CG images, synthesized by employing texture mapping techniques, of marble objects, china teacups, and a china vase, all of which have many cracks on their surfaces. Finally, we discuss further improvements for extending the model to one which works on any curved surface and produces more realistic crack patterns according to the shapes of the surfaces.



     
  • Visual Simulation of Animal


  • A Flight Model for Butterflies Taking into Account the Force Caused by Flapping the Wing
    Y. Anzai, K. Muraoka, N. Chiba and N. Saito

    Abstract:(Japanese)
    Recently, a study of animal computer graphics is made extensively for image representation such as virtual reality; however, a study of insects such as butterfly is less. In this paper, we propose a flight model and how to control it simply for real-time butterfly flight. This technique makes butterflies fly with a flap of the wings. It can represent the typical flight of real butterflies by controlling the model's parameters.


    Motion Simulation of Virtual Varicolored Carp Based on the Vibration
     Wing Theory
    Takahide Manabe, Toshio Harima, Yuichi Anzai, Norishigle Chiba and Nobuji Saito

    Abstract:(Japanese)



     
  • Pictorial Rendering (Non-photo-realistic Rendering)


  • Storoke-based Suibokuga-Like Rendering for Three-Dimensional Geometric Models
    -Ten and Shun Touches-

    Y.Sato, T. Fujimoto, K. Muraoka and N. Chiba

    Abstract:
    Non-photorealistic rendering has become an important research topics in computer graphics in recent years. We have previously proposed a non-photorealistic rendering method to generate Suibokuga-like images of trees. This method was suitable only for representing trees in Mokkotsuho paintings because the images were generated from three-dimensional skeleton data. In this paper, we propose a method to generate Suibokuga-like images of arbitrary objects from three-dimensional geometric models, such as polygonal models. The proposed method realizes Kou, Ten, and Shun brush stroke techniques for creating Sensenbyoho paintings, which are a typical Suibokuga style for representing landscapes. Moreover, the images can be generated from arbitrary viewpoints and light source information. The ability of this method is demonstrated by showing various example.



    Watercolor-Style Rendering of Perspective Drawings
    D. Nakagawa, T. Fujimoto, K. Muraoka and N. Chiba

    Abstract: ( Japanese)
    We propose a method for automatically generating watercolor-style perspective drawings from three-dimensional geometric models. The method would be useful in the architectural-design area. It em-ploys several technical approaches that realize the following general features of real watercolor-style per-spective drawings: the outlines and edges of objects are drawn, there is no overflow of watercolor in the coloring especially of buildings, another objects like botanical trees are rendered often in simplified drawing styles and transparent light colors are used in most cases.



    Generating Pen and Ink Illustrations from Gray-scale Images
    D. Nakagawa, K. Yamaguchi, K. Muraoka and N. Chiba

    Abstract: ( Japanese)
    Recently, in computer graphics, not only photo-realistic-rendering but also non-photo-realistic-rendering is researched briskly. In this paper, focusing on pen-and-ink illustration that is usually put in books or used for technical illustration, we propose a method for generating a pen-and-ink illustration from a given gray-scale image. There are two fundamental styles in pen-and-ink illustration: one is line drawing style that represents an illustration by lines, and the other is stipple drawing style that represents one by dots. If the size of a line or a dot depends on the resolution of display device, we have one serious problem; in low-resolution device, the generated illustration can be given an artifact, that is, artificial pattern caused by the connection of lines or dots. By the method proposed in this paper, such artifact can be reduced using smoothness-line, which is given the fluctuation by 1/f noise, and smoothness-dot.



    Simple Cellular Automaton-based Simulation of Ink Behaviour and Its Application to Suibokuga-like 3D Rendering of Trees
    Qing Zhang,  Youetsu Sato,Jun-ya Takahashi,  Kazunobu Muraoka and Norishige Chiba

    Abstract:
    Suibokuga is a style of monochrome painting characterized by the use of Chinese black ink (sumi), a complex interaction between brush, ink and paper, and such visual features as Noutan (shade), Kasure (scratchiness), and Nijimi (blur). In this paper we present a simple behavioral model of water and ink particles based on a 2D cellular automaton computational model, and its application to a Suibokuga-like rendering of 3D trees. Copyright(C) 1999 John Wiley & Sons, Ltd. 
     



     
  • Fractal

    Wrinkly Surface Generated on Irregular Msh by Using IST Generalized on Code Space and multi-Dimensional Space:Unification of Interpolation Surface and Fractal

    T. Fujimoto, Y. Ohno, K. Muraoka and N. Chiba

    Abstract:
    Interpolation surfaces, such as Bezier or Bspline surface, are usually used for representing smooth manmade objects and provide an excellent ability to control the shape of a surface by intuitively moving control points. In contrast, the fractal technique is used for creating various complex shapes, mainly of natural objects, that have self-similarity using simple procedures. We have proposed the "wrinkly surface (WR surface)" for combining the advantages of interpolation surfaces and fractals. In this paper, we propose the expansion of the construction scheme of the WR surface to irregular meshes. Control points of a WR surface are interpolated using the "Iterated Shuffle Transformation (IST)." Therefore, in order to achieve the expansion, we first generalize the IST on code spaces, and then propose multi-dimensional IST defined on geometric spaces. By creating various shape model examples, we demonstrate the use-fulness of the WR surface as a modeling tool.
    key words: geometric modeling, interpolation surface, fractal, subdivision, iterated function system (IFS)

  •  
    Fractal Deformation Using Displacement Vectors Based on Extended Iterated Shuffle Transformation
    T. Fujimoto, Y. Ohno, K. Muraoka and N. Chiba

    Abstract:   
    In this paper, we propose a framework of "fractal deformation" using displacement vectors based on "extended Iterated Shuffle Transformation (ext-IST)". An ext-unit-IST is a one-to-one and onto mapping that is extended from a unit-IST, which we have proposed, and is basically defined on a code space. When the mapping is applied on a geometric space, a fractal-like repeated structure, which is referred to as "local resemblance in space/scale directions", is constructed on the relationship between points on the domain and those on the range. By applying the mapping to displacement vectors given on a geometric shape, the shape can be deformed in the fractal-like repeated manner. This fractal deformation is easy to control by changing the displacement vectors intuitively. In addition, a continuous transition between a continuous deformation and a fractal deformation can be realized. We demonstrate how the fractal deformation technique produces attractive results by showing various examples.
    Key words: computer graphics (CG), geometric model, shape deformation, fractal, Iterated Function System (IFS) , attractor, Iterated Shuffle Transformation (IST)



     
  • Visual Simulation of Lava Flows


  • Particle-based Visual Simulation of Lava Flows
    Y.Oda, T.fujimoto, K.Muraoka, N.Chiba

    Abstract: ( Japanese)
    ln this Paper, We present a particle-based method for visually simulating lava flows. Employing our developed particle-based simulation models of viscous fluid dynamics and heat transfer, this method realizes the visual features of lava flows: lava flows broaden like a fan form; the viscosity of lava changes according to its temperature; cool downed lava gets hard (hard lava is called crust); the color of lava changes according to its temperature; crust is dark; lava of high temperature run out by breaking crust; etc.



     
  • Visual Simulation of Lightning


  • CG Lightning Model Taking into Account an Electric Field
    B.Sosorbaram, T.Fujimoto, K.Muraoka, N.Chiba

    Abstract: (Japanese)
    Simulation of weather Scenery in computer graphics (CG) is an important issue that has a Wide range of applications related to image content, such as in movies and in various landscape simulations. In general, research to date into CG lightning has focused on generating a lightning pattern by applying probability and statistics techniques, which do not consider the generating mechanism of lightning. In natural lightning, an electric discharge path (stepped leader) is generated under the influence of an electric Geld formed by electri&cation of a cloud. In this Paper, We Prt!Sent a method that generates a lightning pattern by simulating a stepped leader in an electric field defined by placement of electric charges in a cloud and ground.


     

  • Visual Simulation of Collapse


  • A PEM-based Simulation Technique for Animating Collapse
    M.Nakano, T.Fujimoto, N.Chiba

    Abstract: (Japanese)
    Moving objects colliding with one another, such as falling rubble in collapse phenomena, cause complicated motions. In order to effectively produce animations of such objects in computer graphics, a physically-based simulation method is usable and often used. Our aim is to develop a rigid body dynamics simulation method which is simple to understand and easy to implement. In this paper, we propose a method developed by implementing the penalty method that was realized in Particle-Element-Method by assigning Voigt model to both normal-direction and tangential-direction of a particle-sphere, so as to be suitable for three-dimensional polygonal models. Thus we can solve collision, contact, and frictional force in a uniform manner.

     


     

  • Visual Simulation of Sound Generation

  •  

    Efficient Generation of Sound Effects of Trees Swaying in the Wind
    K.Matsuyama, T.Fujimoto, K.Muraoka, N.Chiba

    Abstract: (Japanese)
    We proposed the sound modeling method that automatically produces sound effects of a tree swaying in the wind. In the method, we first apply the different sound effect generation algorithms to branches and leaves. The individual results are then compounded into the whole sound effect of the tree. In this paper, we will present the more efficient generation algorithms for branches and leaves developed by employing the statistical strategies different from the previous ones.



     
  • Miscellaneous


  •  A Method of Constructing Finite Element Method (FEM) Mesh  from Volume Data
    Aki Doi, Yasuhiro Miura and Norishige Chiba

    Abstract:(Japanese)
     
     



     
  • International Conference
     

    Pseudo-dynamics model of a cantilever beam for animating flexible leaves and branches in wind field

    Shaojun Hu, Tadahiro Fujimoto, Norishige.Chiba

    Abstract:
    We present a pseudo-dynamics model of a cantilever beam to visually simulate motions of leaves and branches in a wind field by considering the influence of natural frequency (f0) and damping ratio (e). Our pseudo-dynamics model consists of a static equilibrium model, which can handle the bending of a curved beam loaded by an arbitrary force in three-dimensions, and a dynamic motion model that describes the dynamic response of the beam subjected to turbulence. Using the static equilibrium model, we can apply it to controlling the free bending of petioles and branches. Furthermore, we extend it to a surface deformation model that can deform some flexible laminae. Based on a mass spring system, we analyze the property of dynamic response of a cantilever beam in turbulence with various combinations of f0 and e, and we give some guidelines to determine the combination types of branches and leaves according to their shapes and stiffness. The main advantage of our techniques is that we are able to deform curved branches and some flexible leaves dynamically by taking account of their structures. Finally, we demonstrate that our proposed method is effective by showing various motions of leaves and branches with different model parameters.
    KEY WORDS: cantilever beam; computer animation; leaf deformation; natural phenomena; fBm noise; 1/fb noise



     


    Multidimensional Visual Aid Enhances Haptic Training Simulations

    Osama.Halabi, Norishige.Chiba

    Abstract:
    This paper explores the use of hypotrochoid curves as visual aids for haptic training systems that are used to teach motor skills that require recall of forces and positions at specific locations to replicate the expert touch. The visual aid presented is a multidimensional feedback tool that can provide information on force, position, and velocity simultaneously. The extent of learning is measured by the accuracy of the force recall. A breast haptic simulation was used to test the presented visual aid. Results suggest that multidimensional feedback is an effective way to promote learning of forces. In addition, the presented visual aid made learning an enjoyable process.


     


    Microphone-based Wind Velocity Sensors and Their Application to Interactive Animation

    Kenichi.Kanno, Norishige.Chiba

    Abstract:
    We are developing a simple low-cost wind velocity sensor based on small microphones. The sensor system consists of 4 microphones covered with specially shaped wind screens, 4 pre-amplifiers that respond to low frequency, and a commercial sound interface with multi channel inputs. In this paper, we first present the principle of the sensor, i.e., technique to successfully suppress the influence of external noise existing in the environment in order to determine the wind velocity and the wind direction from the output from a microphone. Then, we present an application for generating realistic motions of a virtual tree swaying in real wind. Although the current sensor outputs significant leaps in a measured sequence of directions, the interactive animations demonstrate that it is usable for such applications, if we could reduce the leaps to some degree.


     


    An Efficient Drawing Method for Laser Projectors

    Purkhet Abderyim, Osama Halabi, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    Laser Projectors are used in the entertainment industry to draw vector-based graphics. In order to present a stable image to the observers, the laser projector moves the beam quickly by using computer-controlled mirrors. The moving speed is high enough so that human eyes perceive it as a line of light. In contrast with other vector graphic devices, laser projectors have their own characteristics, such as flickering, switching the laser on and off, the brightness of the line, and inertia of the reflective mirrors. In this paper we study the efficient way of drawing graphics with a laser projector. In the first part we attempt to solve the blanking lines problem by testing a simple pattern where this effect occurs. Then, we try to compensate the error caused by the inertia effect associated to the different rotation angles of the mirrors. Furthermore In order to avoid the inertial and blank lines effect we combine these two solutions to create a suitable Eulerian graph and propose the efficient drawing sequence using
    graph theory.


     


    Visual Simulation of Broad Leaves Deforming in Wind Field

    Shaojun Hu, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    We present a method to simulate broad leaves deforming by considering the following regulations recognized by botanists: (a) the petioles bend and twist as cantilever beams; (b) many broad-leaved species reconfigured into streamlined objects in high wind; (c) many leaves species fluttered erratically in low wind. We implement (a) using a simplified discretization method to obtain the deflection curve based on beam theory, and we propose a geometric deformation model for leaves reconfiguration in (b). The stochastic motion observed in (c) is implemented by introducing an fBm noise which can control the wind field and waving phenomenon along the leaf margin.
    Keywords: computer animation, natural phenomena, broad leaf, deformation, 1/fβ noise, fβm

     


    Camera-Based Calibration of Multiple Laser Projectors for Collaborative Projection

    Menendez Francisco J., Halabi Osama, Fujimoto Tadahiro, Chiba Norishige

    Abstract:
    In this paper we propose a method to automatically calibrate and combine multiple laser projectors for collaborative projection. One of the main caveats of today’s laser projectors is the relationship between the speed in which the galvanometers can move and the complexity of the data we are trying to display. As image complexity grows, we are forced to increase the scanning speed in order to avoid flickering. However, the inertia effect of the rotating mirrors, which manifests as curved deformations in sharp angles, becomes more evident as we force the speeds up. To improve the way these projectors behave, we propose combining two or more projectors to display one single image. In this way, the amount of lines that can be drawn without flickering would increase, without forcing the galvanometers to move at greater speeds or jumping greater angles. Furthermore, to obtain an accurate calibration, we use a digital camera to capture the drawing area of each singular projector and produce the necessary transformations to allow for a full overlap of these areas.
     


     


    Multi-Purpose Recursive Mapping Method for Animating Large-Scale Cumulonimbus Clouds

     Abdukadir Mamat, Geni Mamtimin, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    Simulation and animation techniques for generating continuously growing clouds with a high degree of reality are very challenging and difficult tasks in computer graphics. In our previous study, we presented a hybrid method of animating cumulus-type cloud growth on a large scale, and have since tried to obtain even more realistic animation of continuous growth of clouds. The hybrid method we present recursively generates continuously growing clouds efficiently in respect of computation time and memory consumption. In this study, we will present an extension method of representing a highly realistic animation of continuously growing clouds with detailed behavior. As the extension, an Inward-Recursive mapping method is presented, which is used together with the previously proposed method, which is called Outward-Recursive mapping. To reduce the uniformity of generated clouds caused by using only one kind of 3D primitive pattern in the mapping process, and to improve the realism of the clouds generated, we prepare multiple 3D primitive patterns and map them recursively in each recursive level. Experimental results show that the proposed method efficiently creates realistic animations of large-scale clouds with more detailed behaviors, accompanied by fast calculation times and low memory requirements.
    Keywords: natural phenomena, cloud growth, IR-mapping, OR-mapping, large-scale animation .
     


    Real-time Sound Generation of Spark Discharge

    Katsutsugu Matsuyama, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    A technology for automatically creating and adding the sound to interactive CG animations of spark discharges in real time has been developed. In the procedure proposed in this paper, the user inputs the electric charge distribution, boundary conditions and other parameters affecting the initiation of electric discharges in virtual space. The animation of the discharge is then created by generating the shape of the discharge pattern and rendering it, and the sound synchronized with the animation is automatically generated
    in real time. The noises from spark discharges are shock waves, which exhibit complicated behavior; but, in this study, an empirical shape for a shock wave is employed to efficiently generate the acoustic waveform. Effective procedures for expressing lightning discharges and continuous discharges are also proposed. 


    Morphing-Based Vectorized Candle Animation for Laser Graphics

    Purkhet Abderyim, Menendez Francisco J, Halabi Osama, Norishige Chiba

    Abstract:
    Although laser projectors are widely used in the practical field (e.g.: laser shows performed at music concerts and other various events), it has not yet been studied from the Computer Graphics research point of view. In this paper, we propose a small library to project Bezier curves using double buffering techniques. This is our first try to develop Computer Graphics technology for making use of laser projectors in an efficient way.


    Vector-Based Library for Displaying Bezier Curves Using a Laser Projector

    Menendez Francisco J, Halabi Osama, Norishige Chiba

    Abstract:
    Although laser projectors are widely used in the practical field (e.g.: laser shows performed at music concerts and other various events), it has not yet been studied from the Computer Graphics research point of view. In this paper, we propose a small library to project Bezier curves using double buffering techniques. This is our first try to develop Computer Graphics technology for making use of laser projectors in an efficient way.


     


    Surface Reconstruction for Particle Simulation Using Level Set Method

    Purkhet Abderyim, Tadahiro Fujimoto, Norishige Chiba and Mamtimin Geni

    Abstract:
    The particle-based method is one of the most commonly used methods of fluid simulation. Although it has certain advantages, surface reconstruction with particles remains a challenging problem. In this paper, we present a new surface representation model for particles. The Eulerian level set method was used for a Lagrangian particle simulation to represent the surface. Particle simulation was calculated using the MPS (Moving Particle Semi-implicit) method. Our method can produce a complex surface with arbitrary topology that follows the irregular movement of particles.


     


    Volumetric Particle Method For Animating Viscous Fluids

    Menendez Francisco J, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    In the present paper, we introduce an efficient volumetric particle-based approximation method for animating viscous fluid flows , such as water, mud and lava flows. The proposed method employs volumetric particles in order to replicate the movement of viscous flows. The dynamics of each particle is determined by estimating the quasi forces, i.e. pressure and inter-attraction force, which vary according to temperature, and elastic collisions. The viscosity is realized virtually by the inter-attraction force. In the present paper, we present detail of the proposed method and demonstrate its applicability and efficiency via animated frames of several types of flows.


     


    Translucent Shadow Mapping For Particle Based Rendering

    Gunjee Zorig, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    VTranslucency is important for realistic graphics since many substances in nature are translucent. This paper presents a new method for real-time rendering of translucent shadows for particle-based rendering. Most of the recent shadow algorithms are inappropriate for point primitives. Our work goes beyond previous work in developing transparency based mapping for a particle type data set. We use our new algorithm, named the
    SPHERICAL MAPPING ALGORITHM. The proposed algorithm works even in the difficult situation where the light sources are inside the translucent object. The algorithm takes as input a particle set and creates mapping tables in each direction in the spherical system. The algorithm uses the particle to light source mapping approach. Each translucent shadow map (TSM) contains depth, opacity and visibility sorting information for given light sources. For a given camera position, the final lighting and shadow are generated by composing appropriate subsets of the mapping tables. This method allows us to render complex translucent objects with varying light and material properties in real time. We also describe implementation details in a recent, programmable GPU (Graphics Processing Unit).


     


    Real-time Rendering of a Large-scale Particle Cloud

    Gunjee Zorig, Sosorbaram Batjargal, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    Visual realism, detail-rich simulation, and real-time processing are growing areas in modern three-dimensional computer graphics. In this paper, we propose a new method for rendering large-scale particle sets. Our method combines the best features of point, volume and polygonal rendering to obtain realistic images. In order to handle a large number of particles, we introduce a novel method of sorting for alpha blending and calculating a light and shadow. This involves a new spherical mapping algorithm which divides large-scale data into a reliable small set of render-oriented subsets. Test results show more than twice the improvement of speed and rendering functionality of works.
    Keywords: real-tine rendering, shadow algorithms, particle system, point cloud, GPU acceleration.


    Particle-based Visual Simulation of Sand Deformation Caused by Wind Blowing

    Mamat Abdukadir , Mamtimin Geni, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    It is considered that the sand dune is a multitude of sand particles. The sand particles move by the effects of wind. The simulation of this effect is a very interesting research field in natural phenomena simulation and computer graphics. In this study, two-dimensional, particle-based simulation of sand deformation caused by wind blowing has been considered. The motions of the sand and wind particles are individually considered. We assume that both the sand motion and the wind motion are incompressible continuum systems and their behavior follows the Navier-Stokes equations. To solve these equations, we applied the moving particle semi-implicit (MPS) method, which has been developed in recent years. Viscosity force is used instead of drag force, although drag force plays an important role in the blowing of sand particles. For the evaluation of the interaction force between the sand and, sand-surface particles, we applied the Particle Element Method. As a result, we simulated the saltation process above the surface, as well as the change between saltation and creep along the surface.
    Keywords: Natural Phenomena, Sand, Wind, Visual simulation, Particle.


     


    Visual Simulation of Wood Aging Caused by Biological Deterioration

    Xin Yin, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    Wood exposed to the elements changes in appearance. To produce realistic computer graphic images, techniques for simulating wood aging phenomena must be studied. Wood deterioration is mainly caused by biological organisms. We propose visual simulation of worm-eaten wood and microorganism growth on the surface of wood. In this technique, an ant colony optimization algorithm is used to generate the pattern of wood aging caused by biological deterioration. Imaginary ants act on the surface of an object and deposit pheromone. The courses traveled by ants can be used to represent worm trails. The pheromone that ants leave on the surface can be used to represent microorganism growth. In order to construct the object surface, wood is represented by a tetrahedral mesh. Surface variation can be controlled by changing the values of vertices in the tetrahedral mesh. Finally, the effectiveness of this method is demonstrated by implemented examples.
    Keywords: Wood, Aging, Worm-eaten, Microorganism, Visual Simulation, Ant Colony Optimization.


     


    Automatic Point Cloud Registration Based on Feature Lines

    Tetsuji Konno, Koichi Konno, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    If an object is restored in a 3D space, the range sensor usually measures the object from some directions and the point clouds obtained from the range sensor are registered. The registration method is divided into two approaches: one is the geometrical transformation performed to coincide the points of clouds and the other is the geometrical transformation performed to coincide feature quantities. In the first approach the registration is time-consuming because some pairs of points must be selected from all points of clouds. In the second approach, the registration will be impossible if feature quantities are not extracted correctly. In this paper, we present a registration algorithm based on a feature-line-matching approach so as to overcome the problems mentioned above. In our method, feature lines are extracted from a point cloud and optimized. Finally, best suited feature lines are selected automatically and the geometrical transformation is performed so that the selected feature lines coincide.


     


    Point Cloud Registration Based on Feature Lines Derived from Depth Difference

    Tetsuji Konno, Koichi Konno, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    In this paper, we present an efficient algorithm for the registration of multiple "point cloud data" obtained by scanning a real object from different viewpoints. This algorithm is based on a "feature-line-matching" approach that evaluates the distance between a pair of feature lines. Thus, our algorithm works well for scanned data such as data of artificial buildings. In our algorithm, the feature lines are detected efficiently by using the coordinate values of "point cloud data".


     


    Recursive Particle Generator for Animation Plum Fluid

    Daiki Takeshita, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    Plume fluid, such as continuously growing smoke or a cloud with an expansive gush, is a difficult phenomenon to represent with a high level of reality. The methods that have been proposed so far are more for representing volcanic smoke or a cumulonimbus cloud. In this paper, we propose a method for animating plume fluid. This method uses particle generators that are continually provided in the simulation space to generate particles recursively. This scheme efficiently represents the characteristic expansion phenomenon of plume fluid. In the model presented in this paper, the motions of particles are determined by a particle-based simulation method which approximately realizes the pressure gradient, viscosity, buoyancy, entrainment, adiabatic cooling, and release of latent heat of a fluid represented as cumulus.


     


    Noise-based Animation of Waving Phenomena

    Tadahiro Fujimoto, Shunsuke Miyauchi, Toru Suzuki, Norishige Chiba

    Abstract:
    In this paper, we propose a framework to produce animations of waving phenomena in simple and efficient
    ways using "fractional Brownian motion (fBm)". As applied examples, two methods are presented. One is a method for animating linear objects waving in wind, such as weeping willow tree branches and grass blades. The motions of these objects are given by determining motion angles of their link models efficiently using fBm. Another is a method for animating breaking waves. The original motions of the waves are obtained using two-dimensional particle-based simulation. These two-dimensional motions are used to produce natural-looking three-dimensional wave motions using fBm.

     


    Thunder Synthesis for Animating Lightning

    Katsutsugu Matsuyama, Hisato Abe, Tadahiro Fujimoto, Norishige Chiba

    Abstract:
    The method for creating a lightning pattern using an electric field and electric charge distribution in a thundercloud has been proposed by Sosorbaram et al. In this paper, we present a technique which automatically adds thunder to a generated lightning pattern. Sound sources are put on the generated lightning pattern, and shock waves are emitted at the time of the lightning pattern generation. We synthesize waveforms at an observer position and create thunder.

     


    A Visual Model of Lightning Lifecycle in Thunderclouds

    Batjargal Sosorbaram, Daiki Takeshita, Tadahiro Fujimoto and Norishige Chiba

    Abstract:
    Since lightning is a natural phenomenon that accompanies a thundercloud, an expression for thundercloud is indispensable for CG simulation. Producing a lightning model with an associated thundercloud is important for applications in games, military training, flight simulations, and so on. In this paper, we propose a model, which describes the lifecycle of lightning activity in a thundercloud and simulates the lightning paths inside the thundercloud and Form the cloud to the ground. The Z-buffer based volume rendering method is used for generating CG images of this model.

    Keywords: Visual simulation, thundercloud, electrification of a thundercloud, lightning

     


    Suibokuga-Like Rendering For Three-Dimensional Geometric Models

    Yoetsu Sato, Tadahiro Fujimoto, Kazunobu Muraoka and Norishige Chiba

    Abstract:
    Non-photo realistic rendering has developed into important research topics in computer graphics in recent years. We have previously proposed a non-photo realistic rendering method to generate Suibokuga-like images of trees. This method was suitable only for representing trees in Mokkotsuho paintings because the images were generated from three-dimensional skeleton data. In this paper, we propose a method to generate Suibokuga-like images of arbitrary objects from three-dimensional geometric models, such as polygonal models. The proposed method realizes Kou, Ten, and Shun brush stroke techniques for creating Sensenbyoho paintings, which are a typical Suibokuga style for representing landscapes. Moreover, the images can be generated from arbitrary viewpoints and light source information. The ability of this method is demonstrated by showing various examples.

    Keywords: non-photorealistic rendering (NPR), Suibokuga-like rendering, three-dimensional geometric model, brush stroke, simulation of ink diffusion, cellular automaton.


     


    Visual Simulation of Wood Weathering Involving Distortion and Cracks

    Xin Yin, Tadahiro Fujimoto and Norishige Chiba

    Abstract:
    Materials exposed to the elements change in appearance because of weathering. Because wood is an organic substance, cracks and the surface erosion occur easily. To produce realistic computer graphic images of weathered wood, a method that simulates the weathering phenomenon is necessary. We propose a visual simulation of the distortion, cracks, and erosion of wood caused by weathering. In this method, wood is represented by a tetrahedral mesh. By setting semi-physical variables at each vertex in this mesh, a simulation of wood weathering can be accomplished. The surface of the wood is defined by the values assigned to the tetrahedral mesh vertices on the surface. Changes in the surface are detected by value changes. The effectiveness of this method is demonstrated by applications involving plank and shapes such as a bunny and Buddha.

    Key word: Wood, Weathering, Crack, Visual Simulation, Modeling, Solid Texture.



    Fractal Deformation Using Displacement Vectors and Their Increasing Rates Based on Extended Unit Iterated Shuffle Transformation

    T. Fujimoro and  N. Chiba

    Abstract:
    In this paper, we propose a new fractal deformation technique. An "extended unit Iterated Shuffle Transformation (ext-unit-IST)'' is a mapping that changes the order of the places of a code on a code space. When it is applied on a geometric space, it constructs a fractal-like repeated structure, named "local resemblance''. In our previously proposed fractal deformation technique, a geometric shape was deformed by applying an ext-unit-IST to displacement vectors (d-vectors) given on the shape. In the new technique proposed in this paper, the ext-unit-IST is applied to the increasing rates of the d-vectors. This allows the d-vectors to change widely without disturbing the shape and improves the deformation quality. Several examples demonstrate the performance of the newly proposed technique.
    Keywords: computer graphics, geometric model,deformation, IFS, IST.


    Particle-Based Simulation of Explosive Flames

    D. Takeshita  S. Ota M. Tamura T. Fujimoto and N. Chiba

    Abstract:
    In the present paper, we propose a particle-based method for the visual simulation of explosive flames. This method consists of a numerical simulation method based on a fluid model described by discrete Lagrangian using particles and a rendering method for generating a CG animation from the movement data of the particles. This fluid model uses flame particles and air particles. The model calculates the buoyancy caueed by the difference in temperature as the external force in the Navier-Stokes equations and approximates the viscous force and pressure via a discrete particle model. In addition, the heat conduction between particles is taken into account. The proposed method realizes the representation of distinctive phenomena such as an ascending airflow with a quantity of explosive flame and a swirling airflow behind the ascending airflow. CG images are rendered using a Z-buffer based volume rendering method.



    (Slides&Videos)

    Animating Tree Movement with Sound Effects Generation

    K. Matsuyama  S. Ota  M. Tamura T. Fujimoto  K. Muraoka  and  N. Chiba

    Abstract:
    This video demonstrates the methods for automatically generating tree motions and sound effects for an animation of branches and leaves moving in the wind. Natural motions of leaves and branches swaying in a wind field are created in real-time by our efficient method without using time-consuming physical simulation techniques based on the equations of motion. This method utilized "1/fβ noise", which is observed in various natural phenomena. Specifically, in this method, the natural motions of leaves and branches are created by calculating appropriate motion angles using 1/fβ noise functions. The realism of the branch motion is enhanced by applying a real-time simulation technique based on the spring model Sound effects are generated as follows: Each tree is divided into branches and leaves, and an independent sound effect generation process is employed for each element. The indidual results are then compounded into one sound effect. For the branches, we employ an approach based on the frequencies of experimentally obtained Karman vortex streets. For the leaves, we use the leaf blade state as the input and assume a virtual musical instrument that used wave tables as the sound source. All computations can be performed independently for each frame step.



    (Slides&Videos)

    Visual Simulation of Lava Flows Employing Particle-based Approach

    Y. Oda  S. Ota  M. Tamura T. Fujimoto  K. Muraoka  and  N. Chiba

    Abstract:
    This video demonstrates our new particle-based method for vistully simulating lava flows. Employing our developed particle-based simulation models of viscous fluid dynamics and heat transfer, this method realize the visual features of lava flows: lava flows broaden like a fan form; the viscosity of lava changes according to its temperature; cooled lava solidifies into crust or new ground; the color of lava changes according to its temperature; crust is dark; lava of high temperature run out by breaking crust; etc.


    1/fβ Noise-Based Real-Time Animation of Trees Swaying

    S. Ota  M. Tamura K. Fujita T. Fujimoto  K. Muraoka  and  N. Chiba

    Abstract:
    Trees are one of the most important elements of natural landscapes. Therefore, in computer graphics, there is a great demand for methods to realize the natural representation of trees in virtual landscapes in various fields such as entertainment industry or environmental assessment in construction. Many studies have been made on techniques in which the shapes of trees are modeled but only a few studies have been reported on methods to incorporate the shapes with motions in a wind field. Most of these studies use physical simulation techniques based on the equations of motion to generate the branch motions and cannot realize the motions of individual leaves. In this paper, we propose a method to create the natural motions of individual leaves and branches swaying in a wind field. This method generates the leaf and branch motions based on "1/fβ noise", which is observed in various natural phenomena. For the branch motion, a simple simulation method based on the spring model is applied to enhance the realism of the motion. This method enables the real-time creation of the leaf and branch motions. Diverse motions according to tree species and shapes and wind conditions can be easily realized by controlling the parameters.
    Keywords: tree, leaf, motion, wind, 1/fβ noise, real-time animation


    Modeling Rocky Scenery Taking into Account Joints

    T. Ito  T. Fujimoto  K. Muraoka  and  N. Chiba

    Abstract:
    In order to estimate a user's head pose at a relative large scale environment for virtual reality (VR) applications, multiple cameras set around him/her are used in conventional approaches, such as a motion capture. This paper proposes a method of estimating head pose from spherical images. A user wears a helmet on which a visual sensor is mounted and the head pose can be estimated by observing the fiducial markers put around him/her. Since a spherical image has a full view, our method can cope with a big head rotation motion compared with a normal camera. Since a head pose at every time is directly estimated from the observed markers, there is no accumulated errors in our method compared with a inertial sensor. Currently, an omnidirectional image sensor is used to acquire the most part of a spherical image in our experiment.


    Wandering in VR Environments by Estimating Head Pose Using an Omnicam

    S. Li, F. Ishizawa and N. Chiba

    Abstract:
    In the walk-through via an Internet, we move a mouse to imitate a walk by our foot [3]. Here, we consider the case which maps a real motion to an immersive virtual reality environment. For example, we wander in computer room as if we do in a museum for watching some arts. The user's head motion at a relative large scale environment is needed to be known for realizing this-kind-like immersive virtual realify. This research proposes a method of estimating the head motion based upon vision approaches for mapping a head motion to an immersive virtual realiy environment. We put fideucial markers around the room to be changed virtually and use an omnidirectional image sensor to observe these markers. By mounting the visual sensor on a helmet,  the head motion of a user who wears the helmet can be estimated by prcessing images captured from the omnidirectional  image sensor. Since it has a 360 degree view, it can cope with a big head rotation motion compared with a normal  camera Since a head motion at every time is directly estimated from the observed markers, there is no accumulated errors in our method compared with a inertial sensor. 
    Keywords: virtual reality environment, omnidirectional image, head pose.


  • Procedural Simulation of Interwoven Structures

    F. Drago, N.Chiba

    Abstract:
    We present a convenient method to simulate the geometry and appearance of interwoven structures for the production of complex scenes. This solution is based on procedural texturing and shading techniques, the macro and micro geometry of materials being simulated by procedural displacement. We demonstrate that in the case studied, displaced surfaces offer a number of benefits over complete geometric modeling or bitmap mapped textures. The system proposed is efficient and easily integrated to the general CG production pipeline.
    Keywords: Interwoven materials, Procedural textures, Displacement mapping, Textile modeling, Visual simulation.


    Modeling Leaf Shapes Using L-systems and Genetic Algorithms
    Y.Rodkaew, S.Siripant, C.Lursinsap, P.Chongstitvatana, T.Fujimoto, N.CHiba

    Abstract:
    This work presents a method that combines two techniques: L-systems and Genetic Algorithms (GA) to search for a rewriting expression describing leaf shapes. An L-system is used to construct the shape of a given rewriting expression and GA is used to search for the rewriting expression's fitting parameters. The replacement of real value parameters with tag- functions is introduced. The result shows that the proposed method produces an acceptable output.
    Key words: CG, Natural Phenomena, Modeling, Leaf, L-systems, Genetic Algorithms.
     


    Fractal Deformation Based on Extended lterated Shuffle Transformation
    T.Fujimoto, Y.Ohno, K.Muraoka, N.Chiba

    Abstract:
    In this paper, we propose a framework of "fractal deformation" based on "extended Iterated Shuffle Transformaiion (exi-IST)". An ext-IST is a one-to-one and onto mapping that is extended from an IST, which we have proposed, and is basically defined on a code space. When the mapping is applied on a geometric space, a fractal-like repeated structure, which is referred to as "local resemblance in space/scale directions", is constructed on the relationship between points on the domain and those on the range. By applying the mapping to the deformation of a geometric object, the shape of the object can be deformed in the fractal-like repeated manner. In addition, a continuous transition between a traditional continuous deformation and a fractal deformation can be realized. We demonstrate how the fractal deformation technique produces attractive results by showing various examples.
     


    Simulation of Peeling using 3D-Surface Cellular Automata
    S.Gobron and N.Chiba

    Abstract:
    This paper describes a method for modeling the natural peeling phenomenon over any 3D surface. Using crack input data-precomputed with a semi-physical solution-this method allows simulating peeling on any type of triangulated 3D object. Our model's main advantage is that it proposes an method that is intuitive enough to make it easy to understand and convenient to apply, user controllable, and easily extensible-especially to simultaneous natural phenomena. We first introduce the general development of peeling over various materials. Then, we present how to define groups of peeling, how to determine a realistic and natural peeling order; and how to simulate the rendering of two types of special peelings. Finally, a set of graphical results concludes the paper, presenting a series of direct peeling and curling patterns using classical paintings or plastic-paintings simulated materials.
    Keywords. Computer Graphics, Cellular Automaton, 3DSCA, Peeling, Surface Simulation, multi-layer modeling Natural Phenomena

     


    Visual Simulation of Lightning Taking into Account Cloud Growth
    B.Sosorbaram, T.Fujimoto, K.Muraoka and N.Chiba

    Abstract:
    Simulation of weather scenery in computer graphics (CG) is an important issue that has a wide range of applications related to image content, such as in movies and in various landscape simulations. In general, research to date into CG lightning has focused on generating a lightning pattern by applying probability and statistics techniques, which do not consider the generating mechanism of lightning. In natural lightning, an electrical-discharge path (stepped leader) is generated under the influence of an electric field formed by electrication of a cloud. In this paper, we present a method that generates a lightning pattern by simulating a stepped leader in an electric field defined by placement of electric charges. We also give rendering methods for lightning in a cloud that are based on the volume rendering method using point light sources.

     


    Crack Pattern Simulation Based on 3D Surface Cellular Automaton
    S.Gobron and N.Chiba

    Abstract:
    This article describes a method for modeling the propagation of cracks on any 3D surface. Taking a previous cellular automata model as basis [13] this method allows about any type of cracks on any type of triangulated 3D object. Our model's main advantage is that it proposes a semi-physical solution, making it at the same time user controllable and easily extensible. After summarizing works in the literature, we make a brief and simple description of what physically are cracks and how they are generated. Based on this idea, we detail our model of crack propagation. We first introduce the general development of cracks. We then propose our original model of spectrum stress. This is followed by the description of the mutual interaction between cracks and stresses. Finally, a set of graphical example, with their respective parameters, concludes this paper



    Visual Simulation of Crack Pattern Based on 3D Surface Cellular Automaton
     S.Gobron and N.Chiba

    Abstract:
    This article describes a method for modeling the propagation of cracks on any 3D surface. Taking a previous cellular automata model as basis [13], this method allows about any type of cracks on any type of triangulated 3D object. Our model's main advantage is that it proposes a semi-physical solution, making it at the same time user controllable and easily extensible. After summarizing works in the literature, we make a brief and simple description of what physically are cracks and how they are generated. Based on this idea, we detail our model of crack propagation. We first introduce the general development of cracks. We then propose our original model of spectrum stress. This is followed by the description of the mutual interaction between cracks and stresses. Finally, a set of graphical examples, with their respective parameters, concludes this paper



    Visual Simulation of Snowfall, Snow Cover and Snowmelt
    S.Gobron and N.Chiba

    Abstract:
    Creation of seasonal scenery images by computer graphics is an attractive theme with many problems to be solved. This paper presents a method of expressing snow to create natural scenery image in winter. We describe a method of automatically creating the behavior of snowflakes in a field of air currents with respect to snow fall, a method of automatically creating shapes of snow accumulation by using virtual temperature as a parameter with respect to snow cover formled just after snow fall, and a method based on heat propagation simulation taking into account sunlight, ground heat, and radiation heat from objects with respect to snowmelt. This paper furthermore presents an image creation method to express the feel of the material of snow fall and snow cover



    Origami Modeling Method of Leaves of Plants and CG Image Generation of Flower Arrangement
    K.Kaino and N.Chiba

    Abstract:
    When certain types of digitate leaves are folded up along their main veins as in leaf buds, their margins of leaves are found to form a simple curve or a few lines. From the viewpoint that the venation and the folding leaf buds would be closely related each other, we will propose a origami modeling method. By use of this method, it is shown that complex digitate shapes such as Acer, Cacalia yatabei and Humulus lupulus would be well produced. We will apply this method to get grass stems and twigs of trees and then generate their CG images. We will see that the poetic beauty of wild plants is well produced by our method. To show this fact we will generate CG images of flower arrangement with plants obtained by our method.



    CG Simulation of Natural Shapes of Botanical Trees Based on Heliotropism and Dormancy Break
    N.Chiba, S.Ohkawa, K.Muraoka and M.Miura

    Abstract:
    Realistic image synthesis of botanical trees has many applications. Since the generation of "tree skeletons" having natural visual impressions is essential to the realistic image synthesis, various modeling methods of skeletons, especially growth models, have been presented. However, no one has succeeded in simulating natural tree features which appear in a growth process, such as generation of a round tree crown, a weeping bough, an irregular branching pattern, or regeneration of a crown. This paper demonstrates, by showing several simulated examples, that a growth model having the abilities of heliotropism and dormancy break, which produces shapes of trees adapted to changes in the light environment, is effective in the CG simulation of realistic tree skeletons. Moreover, we will introduce our related research results, that is, CG techniques for simulating branches swaying in the wind and for representing seasonal mountain scenery.



    Terrain Simulation Based on the Recursive Refinement of Ridge-Lines
    N.Chiba, K.Muraoka, K.Yaegashi and M.Miura

    Abstract:
    Since CG Simulation of natural terrain has application in many areas, various modeling methods of terrain including imaginary forgeries have been developed. In this paper, we present a new approach which is suitable for modeling such imaginary mountains produced by erosion processes. Such terrain can not be simulated by standard fractal surfaces. Our algorithm synthesizes the forgery of natural mountain by refining the given initial ridge-lines which reflect the outline of the ideal forgery. The refinement is established by adding derivative ridge-lines recursively to those produced so far. Although we can recognize ridge-lines as a notable geographical feature of mountains produced especially by erosion processes, no such modeling method has been designed so far.