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.
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.
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.
Abstract:(Japanese)
Abstract:(Japanese)
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.
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.
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.
Abstract:(Japanese)
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.
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.
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.
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.
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.
Abstract:(Japanese)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Abstract:(Japanese)
Abstract:(Japanese)
Abstract:(Japanese)
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.
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.
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.
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.
Abstract:(Japanese)
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.
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.
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.
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.
Wrinkly Surface Generated on Irregular Msh by Using IST
Generalized on Code Space and multi-Dimensional Space:Unification of
Interpolation Surface and Fractal
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)
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)
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.
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.
A PEM-based Simulation
Technique for Animating Collapse
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.
Efficient Generation of Sound
Effects of Trees Swaying in the Wind
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.
Abstract:(Japanese)
Pseudo-dynamics model of a cantilever beam for animating flexible leaves and branches in wind field
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
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
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
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
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
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
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
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
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
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 FluidsMenendez 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
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
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.
Animating Tree Movement with Sound Effects Generation
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.
Visual Simulation of Lava Flows Employing Particle-based Approach
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
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
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
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
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.
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.
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.
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
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
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
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.
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.
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.