EG2000

Permanent URI for this community

https://diglib.eg.org/handle/10.2312/218

Browse

Now showing 1 - 20 of 39

An Accurate Illumination Model for Objects Coated with Multilayer Films
(Eurographics Association, 2000) Hirayama, H.; Kaneda, K.; Yamashita, H.; Monden, Y.
This paper proposes an accurate illumination model for rendering objects coated with multilayer films. Optical phenomenaof multilayer films are caused by reflection, refraction, interference, and absorption of light inside each layer of multiple films, and these physical phenomena are complicatedly related with each other. The proposed method calculates composite reflectance and transmittance of multilayer films, taking into account all the physical phenomena described above, and visualizes the optical phenomena caused by the multilayer films accurately. The illumination model proposed in the paper can handle both smooth surface and locally smooth rough surfaces. Several examples of objects coated with various kinds of films demonstrate the usefulness of the proposed method.
Combining finite element deformation with cutting for surgery simulations
(Eurographics Association, 2000) Nienhuys, Han-Wen; van der Stappen, A. Frank
Interactive surgery simulations have conflicting requirements of speed and accuracy. In this paper we show how to combine a relatively accurate deformation model—the Finite Element (FE) method—and interactive cutting without requiring expensive matrix updates or precomputation. Our approach uses an iterative algorithm for an interactive linear FE deformation simulation. The iterative process requires no global precomputation, so runtime changes of the mesh, i.e. cuts, can be simulated efficiently. Cuts are performed along faces of the mesh; this prevents growth of the mesh. We present a provably correct method for changing the mesh topology, and a satisfactory heuristic for determining along which faces to perform cuts. The incision surface will be jagged; this problem is a subject of current research.
Geometric Signal Processing on Polygonal Meshes
(Eurographics Association, 2000) Taubin, G.
Very large polygonal models, which are used in more and more graphics applications today, are routinely generated by a variety of methods such as surface reconstruction algorithms from 3D scanned data, isosurface construction algorithms from volumetric data, and photogrametric methods from aerial photography. In this report we provide an overview of several closely related methods developed during the last few yers, to smooth, denoise, edit, compress, transmit, and animate very large polygonal models.
Geometric Modeling Based on Polygonal Meshesv
(Eurographics Association, 2000) Kobbelt, Leif P.; Bischoff, Stephan; Botsch, Mario; Kähler, Kolja; Rössl, Christian; Schneider, Robert; Vorsatz, Jens
While traditional computer aided design (CAD) is mainly based on piecewise polynomial surface representations, the recent advances in the efficient handling of polygonal meshes have made available a set of powerful techniques which enable sophisticated modeling operations on freeform shapes. In this tutorial we are going to give a detailed introduction into the various techniques that have been proposed over the last years. Those techniques address important issues such as surface generation from discrete samples (e.g. laser scans) or from control meshes (ab initio design); complexity control by adjusting the level of detail of a given 3D-model to the current application or to the available hardware resources; advanced mesh optimization techniques that are based on the numerical simulation of physical material (e.g. membranes or thin plates) and finally the generation and modification of hierarchical representations which enable sophisticated multiresolution modeling functionality.
Robust Polygons Clipping to Model Complex Objects
(Eurographics Association, 2000) Segura, Rafael J.; Feito, Francisco R.
One of the most important problems to solve in Solids Modelling is computing the boolean operations for solids (union, intersection and difference). In order to implement these three operations an algorithm to compute the intersection between faces is needed (polygons clipping). In the case of solids with planar faces there are many solutions, although most of them are valid only when the faces are convex. In this paper we present an algorithm to determine the intersection between polygons of any nature (concave or convex, manifol or non-manifold, with or without holes, etc.) based on the idea of simplicial coverings proposed by Feito 11. One of the advantages of this approach is the robustness of algorithms, since decompositions or complex operations that may alter the results obtained are not avoided. A very interesting application of this algorithm is the modelling of complex solids with this type of polygons as faces.
Spreading of the cultural heritage by means of multi-configurable, low cost virtual reality techniques
(Eurographics Association, 2000) Flores, J.; Arias, J.; Saavedra, S.; Varela, E.; Ferro, J. M.; Taboada, J.
In the last few years, computer graphics techniques have been applied to preserve and promote the cultural heritage. In this first steps the bottleneck of these applications developed was the price of the hardware that limited the use of these tools to museums or exhibition rooms. Nevertheless, the fast increase of graphic capacity of the computers allows the development of high -quality complex applications which can be visualized in personal computers. This is completed by multidisciplinary research groups that focus their efforts on the most relevant aspect of the learning and presence sense in virtual environments. In this paper, an application of V.R. techniques to the promotion of heritage patrimony bases, in a PC platform, is presented. Focus has been put into high screen quality, multiple screen, multi-user, stereoscopic image, 3D sound and multisensorial environments as well as the high transportability, scalability and low price aiming at a quite widespread use of this hardware. The virtual reality application developed shows the old part of Santiago de Compostela, European City of Culture for the year 2000. The model of t he city is complex enough to prove that it is possible to use PC´s as visualization engine, over high quality and complex models.
Volumetric Textures
(Eurographics Association, 2000) Gonzalez Clua, Esteban W.; Dreux, Marcelo
There are some types of nature elements that are adequately represented in Computer Graphics only through volumes. In order to visualize scenes with volumes, together with geometrical objects, it is necessary to make use of a hybrid rendering algorithm. However, the presence of volumetric elements heavily increases the visualization processing time, independently of the technique being used. This article presents a method that is being developed in order to reduce the volumetric rendering to a projection of a special texture on a geometric surface that surrounds the volume. This technique seems to be particularly efficient to volumes that represent nature elements, such as gases, clouds and smoke. It is possible, however, to extend the method to other types of volumetric objects.
Efficient Evaluation of the Field Functions of Soft Objects Using Interval Tree
(Eurographics Association, 2000) Min, Kyung-Ha; Lee, In-Kwon; Park, Chan-Mo
We present an algorithm to evaluate the field function of a soft object efficiently. Instead of using a global field function that is defined by the sum of all local field functions, we consider only the set of local field functions that affects a point at which we want to evaluate the field function. To find the affecting local field functions efficiently, we exploit a data structure called interval tree based on the bounding volume of the component corresponding to the primitives (skeletons) of a soft object. The bounding volume of each component is generated with respect to the radius of a local field function of the component, threshold value, and the relations between the components and other neighboring components. The proposed scheme of field function evaluation can be used in many applications for soft objects such as modeling and rendering, especially in interactive modeling process.
Interactive Vegetation Rendering with Slicing and Blending
(Eurographics Association, 2000) Jakulin, Aleks
Detailed and interactive 3D rendering of vegetation is one of the challenges of traditional polygon-oriented computer graphics, due to large geometric complexity even of simple plants. In this paper we introduce a simplified image-based rendering approach based solely on alpha-blended textured polygons. The simplification is based on the limitations of human perception of complex geometry. Our approach renders dozens of detailed trees in real-time with off-the-shelf hardware, while providing significantly improved image quality over existing real-time techniques. The method is based on using ordinary mesh-based rendering for the solid parts of a tree, its trunk and limbs. The sparse parts of a tree, its twigs and leaves, are instead represented with a set of slices, an imagebased representation. A slice is a planar layer, represented with an ordinary alpha or color-keyed texture; a set of parallel slices is a slicing. Rendering from an arbitrary viewpoint in a 360 degree circle around the center of a tree is achieved by blending between the nearest two slicings. In our implementation, only 6 slicings with 5 slices each are sufficient to visualize a tree for a moving or stationary observer with the perceptually similar quality as the original model.
Visibility Complexity of a Region in Flatland
(Eurographics Association, 2000) Rigau, Jaume; Feixas, Miquel; Sbert, Mateu
The aim of this paper is to study the visibility complexity of different regions in a 2D scene. Based on mutual information, which we used in our previous work to define scene complexity, we propose two measures that quantify the complexity of a region from two different points of view. The knowledge of the complexity of a region can be useful to determine how difficult it is to recompute the visibility links for an animation depending on the regions visited or to obtain the complexity of the movement of a robot. We also envisage its applicability to obtain an optimal load balancing in a parallel computation by dividing the geometry in equal complexity regions.
Recent Advances in Visualization of Volumetric Data
(Eurographics Association, 2000) Brodlie, Ken; Wood, Jason
In the past few years, there have been key advances in the three main approaches to the visualization of volumetric data: isosurfacing, slicing and volume rendering, which together make up the field of volume visualization. In this report we set the scene by describing the fundamental techniques for each of these approaches, using this to motivate the range of advances which have evolved over the past few years. In isosurfacing, we see how the original marching cubes algorithm has matured, with improvements in robustness, topological consistency, accuracy and performance. In the performance area, we look in detail at pre-processing steps which help identify data which contributes to the particular isosurface required. In slicing too, there are performance gains from identifying active cells quickly. In volume rendering, we describe the two main approaches of ray casting and projection. Both approaches have evolved technically over the past decade, and the holy grail of real-time volume rendering has arguably been reached. The aim of this Eurographics 2000 STAR is to pull these developments together in a coherent review of recent advances in volume visualization.
Towards Communicating Agents and Avatars in Virtual Worlds
(Eurographics Association, 2000) Nijholt, Anton; Hondorp, Hendri
We report about ongoing research in a virtual reality environment where visitors can interact with agents that help them to obtain information, to perform certain transactions and to collaborate with them in order to get some tasks done. In addition, in a multi-user version of the system visitors can chat with each other. Our environment is a laboratory for research and for experiments with users interacting with agents in multimodal ways, referring to visualized information and making use of knowledge possessed by domain agents, but also by agents that represent other visitors of this environment. We discuss standards that are under development for designing such environments. Our environment models a local theatre in our hometown. We discuss our attempts to let this environment evolve into a theatre community where we do not only have goal-directed visitors buying tickets, but also visitors that that are not yet sure whether they want to buy or just want information or visitors who just want to look around, talk with others, etc. It is shown that we need a multi-user and multi-agent environment to realize our goals and that we need to have a unifying framework in order to be able to introduce and maintain different agents and user avatars with different abilities, including intellectual, interaction and animation abilities.
Principles of Computer Graphics: the experience of a class A user
(Eurographics Association, 2000) Cailliau, Robert
Computer graphics has gone a long way from the early days in the 50’s and 60’s. Today we have the web, and it’s all visual that is the fashion. What does an unsuspecting user of computers, who is not a specialist, actually experience? Where are we when we leave the 3D interactive shooting game world and we want to do some simple things?
Collaboration in VEs − fact or fiction?
(Eurographics Association, 2000) Hubbold, Roger J.
The growth of the Internet, and company intranets, fuelled by the promise of sophisticated on−line services, has raised expectations of rich collaborative virtual environments, in which humans can indulge in cooperative problem solving. Pioneering demonstrations, such as the work of NASA on rehearsing maintenance tasks for the Hubble telescope, and recent moves into on−line multi−user gaming, have given us a glimpse of what may be possible in a restricted context. And yet, for most users the reality is somewhat different. Interaction in virtual environments is hard enough with only a single user. Add to this the problems of multiple users, collaborating over a network, and we still seem some way from having a really useful, or even usable, tool. The problems span technology (faster, lower latency networks will help, but will not, by themselves solve the problem), software architectures (just how do we ensure a coherent view of a shared environment for multiple users?), to psychology and human factors (we need experiments to quantify how well things work). Above all, how do we come up with solutions which not only work but are accessible to, and usable by, ordinary programmers and end−users? In this talk I will explore some of these problems and describe our own attempts at addressing them.
Virtual Humans: Ten Problems Still Not Completely Solved
(Eurographics Association, 2000) Thalmann, Daniel
During the 1980s, the academic establishment paid only scant attention to research on the animation of virtual humans. Today, however, almost every graphics journal, popular magazine, or newspaper devotes some space to Virtual Humans and their applications. But, there are still a lot of problems to generate believable Virtual Humans. The purpose of this paper is to identify ten main problems to solve to create and animate believable Virtual Humans.
Visual Perception in Realistic Image Synthesis
(Eurographics Association, 2000) McNamara, A.; Chalmers, A.; Trocianko, T.
Realism is often a primary goal in computer graphics imagery, we strive to create images that are perceptually indistinguishable from an actual scene. Rendering systems can now closely approximate the physical distribution of light in an environment. However, physical accuracy does not guarantee that the displayed images will have authentic visual appearance. In recent years the emphasis in realistic image synthesis has begun to shift from the simulation of light in an environment to images that look as real as the physical environment they portray. In other words the computer image should be not only physically correct but also perceptually equivalent to the scene it represents. This implies aspects of the Human Visual System (HVS) must be considered if realism is required. Visual perception is employed in many different guises in graphics to achieve authenticity. Certain aspects of the human visual system must be considered to identify the perceptual effects that a realistic rendering system must achieve in order to effectively reproduce a similar visual response to a real scene. This state-of-the-art report outlines the manner in which knowledge about visual perception is increasingly appearing in state-of-the-art realistic image synthesis. This STAR is organised into three sections, each exploring the use of perception in realistic image synthesis, each with slightly different emphasis and application. First, perception driven rendering algorithms are described, these algorithms focus on embedding models of the Human Visual System (HVS) directly into global illumination computations in order to improve their efficiency. Then perception based image quality metrics, which aim to compare images on a perceptual rather than physical basis are presented. These metrics can be used to evaluate, validate and compare imagery. Finally, Tone Reproduction Operators, which attempt to map the vast range of computed radiance values to the limited range of display values, are discussed.
Discrete Analysis for Antialiased Lines
(Eurographics Association, 2000) Boyer, V.; Bourdin, J. J.
This paper presents a new fast and smooth antialiasing technique. Drawing straight line is the graphic tool’s main primitive. Previous antialiasing techniques improve smoothness but slow down computation.
The 3D Model Acquisition Pipeline
(Eurographics Association, 2000) Bernardini, Fausto; Rushmeier, Holly
Three-dimensional image acquisition systems are rapidly becoming more affordable, especially systems based on commodity electronic cameras. At the same time, personal computers with graphics hardware capable of displaying complex 3D models are also becoming inexpensive enough to be available to a large population. As a result, there is potentially an opportunity to consider new virtual reality applications as diverse as cultural heritage and retail sales that will allow people to view realistic 3D objects on home computers. Although there are many physical techniques for acquiring 3D data – including laser scanners, structured light and time-of-flight – there is a basic pipeline of operations for taking the acquired data and producing a usable numerical model. We look at the fundamental problems of range image registration, line-of-sight errors, mesh integration, surface detail and color, and texture mapping. In the area of registration we consider both the problems of finding an initial global alignment using manual and automatic means, and refining this alignment with variations of the Iterative Closest Point methods. To account for scanner light-of-sight errors we compare averaging and conformance approaches. In the area of mesh integration, that is finding a single mesh joining the data from all scans, we compare various methods for computing interpolating and approximating surfaces. We then look at various ways in which surface properties such as color (more properly, spectral reflectance) can be extracted from acquired imagery. Finally, we examine techniques for a producing a final model representation that can be efficiently rendered using graphics hardware.
Visualizing Stars and Emission Nebulas
(Eurographics Association, 2000) Nadeau, David R.; Genetti, Jon D.; Napear, Steve; Pailthorpe, Bernard; Emmart, Carter; Wesselak, Erik; Davidson, Dennis
We describe star and nebula visualization techniques used to create a 3D volumetric visualization of the Orion Nebula. The nebula’s ionization layer is modeled first as a surface model, derived from infrared and visible light observations. The surface model is imported into a volume scene graph-based visualization system that uses procedural volume modeling to simulate the nebula’s emissive gas layers. Additional scene graphs model proplyds and shock fronts within the nebula. Stars are rendered using Gaussian spots that are attenuated with distance. Finally, eighty-six separate volumes are voxelized from these scene graphs, then simultaneously volume rendered.
An Image Processing Approach to Detection of Ridges and Ravines on Polygonal Surfaces
(Eurographics Association, 2000) Belyaev, Alexander; Ohtake, Yutaka
Surface creases, ridges and ravines, provide us with important information about the shapes of 3D objects and can be intuitively defined as curves on a surface along which the surface bends sharply. Exploring similarity between edges of 2D grey-scale images and curvature extrema of 3D shapes and generalizing a basic edge detection approach to triangular meshes, we develop a method for detection of ridges and ravines on a smooth surface approximated by a triangular mesh. We also sketch three potential applications of our approach: mesh fairness evaluation, improving mesh decimation techniques, and simulating artistic pen-and-ink drawings of 3D objects.

Browse

Browsing EG2000 by Issue Date

Results Per Page

Sort Options