EG2001

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https://diglib.eg.org/handle/10.2312/223

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A Microfacet Based Coupled Specular-Matte BRDF Model with Importance Sampling
(Eurographics Association, 2001) Kelemen, Csaba; Szirmay-Kalos, Laszlo
This paper presents a BRDF model based on the analysis of the photon collisions with the microfacets of the surface. The new model is not only physically plausible, i.e. symmetric and energy conserving, but provides other important features of real materials, including the off-specular peak and the mirroring limit case. Using theoretical considerations the reflected light is broken down to a specular component representing single reflections and a matte component accounting for multiple reflections and re-emissions of previously absorbed photons. Unlike most of the previous models, the proportion of the matte and specular components is not constant but varies with the viewing angle. In order to keep the resulting formulae simple, several approximations are made, which are quite accurate but allow for tabulation, fast calculation and even for accurate importance sampling.
Volumetric Model Repair for Virtual Reality Applications
(Eurographics Association, 2001) Kolb, Andreas; John, Lars
Repairing Virtual Reality (VR) models is a challenge for productive applications. This paper describes a fast implementation of Nooruddin and Turk’s ray-stabbing method 14 based on standard graphics hardware. Raystabbing is used to convert a polygonal model into a volume model (also called voxelization). The volume model is back-converted into a polygonal model using the marching cubes (MC) algorithm 12 and the QSlim algorithm 7 for reducing the extracted polygon model. The overall process yields a properly closed polygonal model with no visual unimportant features like nested or overlapping geometries or unwanted cracks. The voxelization process is the key part of the reparation process. We discuss implementation details and essential problems of ray-stabbing not addressed by Nooruddin and Turk 14.We focus on the generation of the volume model utilizing OpenGL hardware support. The current implementation is a snapshot of an ongoing work at EADS Airbus, Europes leading commercial aircraft company. The final goal is a fast model repair and reduction workflow for generating VR-models and various levels of detail. Problems erase from the fact, that the polygonalization of the volume model using the MC-algorithm generates a far too fine tessellated model which then has to be reduced again. We also discuss possible approaches to overcome this drawback.
Deformable Terrain Generation for Real-time Strategy Game
(Eurographics Association, 2001) Davison, Christopher; Tang, Wen
In this paper, we present a system that has the ability to deform terrain for Real-time Strategy Game with general PC hardware specifications. Various effects could be simulated in real-time such as raising and lowering the ground, creating a large chasm, or levelling the terrain. Effects such as ordering a unit to fire that then destroys part of a mountain could also be replicated. We present our implementations and techniques in using terrain deformation algorithms, Real-time Optimally Adapting Meshes, texture design and terrain generations. An analysis of the speed and memory usage of the system with respect to different PC hardware systems is also presented.
State of the Art in Interactive Ray Tracing
(Eurographics Association, 2001) Wald, Ingo; Slusallek, Philipp
The term ray tracing is commonly associated with highly realistic images but certainly not with interactive graphics. However, with the increasing hardware resources of today, interactive ray tracing is becoming a reality and offers a number of benefits over the traditional rasterization pipeline. The goal of this report is to provide a better understanding of the potential and challenges of interactive ray tracing. We start with a review of the problems associated with rasterization based rendering and contrast this with the advantages offered by ray tracing. Next we discuss different approaches towards interactive ray tracing using techniques such as approximation, hybrid rendering, and direct optimization of the ray tracing algorithm itself. After a brief review of interactive ray tracing on supercomputers we describe implementations on standard PCs and clusters of networked PCs. This system improves ray tracing performance by more than an order of magnitude and outperforms even high-end graphics hardware for complex scenes up to tens of millions of polygons. Finally, we discuss recent research towards implementing ray tracing in hardware as an alternative to current graphics chips. This report ends with a discussion of the remaining challenges and and the future of ray tracing in interactive 3D graphics.
Improvement of the printing model in multi-colored and multi-woodblock virtual printing
(Eurographics Association, 2001) Mizuno, Shinji; Ushida, Akihide; Okada, Minoru; Toriwaki, Jun-ichiro; Yamamoto, Shinji
In this paper, we propose a physically based model for the printing process in the virtual woodblock printing for improvement of printing quality. Virtual printing is a simulation of real printing using “woodblocks”, “a paper sheet”, “a baren (Japanese squeegee)”, and “inks” in a virtual 3D space. A print is synthesized by an interaction among them, and it is very important to study physical properties and behaviors of the virtual items. We focus on the property and the behavior of ink and study a variety of effects due to the degree of moisture of the ink.
Are Points the Better Graphics Primitives?
(Eurographics Association, 2001) Gross, Markus
Since the early days of graphics the computer based representation of three-dimensional geometry has been one of the core research fields. Today, various sophisticated geometric modelling techniques including NURBS or implicit surfaces allow the creation of 3D graphics models with increasingly complex shape. In spite of these methods the triangle has survived over decades as the king of graphics primitives meeting the right balance between descriptive power and computational burden. As a consequence, today's consumer graphics hardware is heavily tailored for high performance triangle processing. In addition, a new generation of geometry processing methods including hierarchical representations, geometric filtering, or feature detection fosters the concept of triangle meshes for graphics modelling. Unlike triangles, points have amazingly been neglected as a graphics primitive. Although being included in APIs since many years, it is only recently that point samples experience a renaissance in computer graphics. Conceptually, points provide a mere discretization of geometry without explicit storage of topology. Thus, point samples reduce the representation to the essentials needed for rendering and enable us to generate highly optimized object representations. Although the loss of topology poses great challenges for graphics processing, the latest generation of algorithms features high performance rendering, point/pixel shading, anisotropic texture mapping, and advanced signal processing of point sampled geometry. This talk will give an overview of how recent research results in the processing of triangles and points are changing our traditional way of thinking of surface representations in computer graphics - and will discuss the question: Are Points the Better Graphics Primitives?
Individualising Human Animation Models
(Eurographics Association, 2001) Ju, Xiangyang; Siebert, J. Paul
Realistic human body animation requires accurate body geometry, realistic textures and believable behaviours. Existing human animation models provide excellent tools to control articulated motion and body surface deformations according to body postures, but modelling a specific individual requires a large degree of skill to sculpt a model resembling that individual. The advent of 3D imaging collection techniques means that the highly accurate 3D surface of a specific person can now be collected in a matter of milliseconds, but most captured 3D surfaces have little semantic information. Consequently, a significant degree of laborious manual intervention is still required to produce a virtual character from their 3D image using traditional animation approaches. The authors present a method for combining 3D images of real people with existing nonspecific, i.e. generic, human animation models to achieve highly realistic human animation models of the 3D imaged individuals. This has been achieved by developing a two-step method for conforming a generic human animation model to fit or “clone” the 3D geometry captured from a specific individual. A segmentation procedure is first applied to the 3D imaged human body surfaces to impose a semantic labelling of the data into body surface parts. Having thereby established correspondence between the segments of the scanned human body and those of the generic model, a rigid body transformation followed by a global 3D mapping is applied to bring the generic mesh into approximate alignment with the 3D imaged model. The second step comprises a conformation procedure driven by (minimising) the distance between the closestpoints between the respective meshes to bring the generic model surfaces into close alignment with those of the real-world 3D surfaces.
Real-Time Procedural Animation of Trees
(Eurographics Association, 2001) Barron, Jeremy T.; Sorge, Brian P.; Davis, Timothy A.
Creating models of living flora, such as trees and grass, has been a challenge in computer graphics for many years. Animating these objects to move realistically in reaction to natural phenomena, such as wind and rain, presents an even greater challenge. In this project, we explore the combination of particle systems with the Lindenmayer model for representing trees to create a realistic simulation of tree movement in response to wind. Our approach, however, is general enough to handle tree animation in response to a variety of other world forces, such as rain, snow, or seismic activity.
Local Versus Global Triangulations
(Eurographics Association, 2001) Linsen, Lars; Prautzsch, Hartmut
Free form surfaces are commonly represented by triangular or quadrilateral meshes. Often these meshes are obtained from unorganized point sets sampled from some object’s surface. We show that local rather than global triangulations of point sets are equally well suited for object representations and that the local triangulations proposed in this paper may even lead to fast triangulation routines.
Why Games Will Be the Preeminent Art Form of the 21st Century
(Eurographics Association, 2001) Hecker, Chris
Computer games share many artistic and technical characteristics with films of the early 1900s. Games' artistic evolution is hampered by the lack of artistic respect from society at large, and the lack of technical standards that would allow artistic innovation. The same problems affected cinema during its birth. During the early 20th century, film managed to find its way from popular diversion to highly respected art form. Will games follow the same course, or will they be stuck forever in the ghetto of pop culture? What technological and artistic changes need to occur in the medium for games to evolve beyond merely shooting aliens and into an art form worthy of association with painting, music, writing, and film? This talk will pose some of those questions, if not attempt to answer them.
SVG Primer
(Eurographics Association, 2001) Duce, David
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Collision Detection for Continuously Deforming Bodies
(Eurographics Association, 2001) Larsson, Thomas; Akenine-Möller, Tomas
Fast and accurate collision detection between geometric bodies is essential in application areas like virtual reality, animation, simulation, games and robotics. In this work, we address the collision detection problem in applications where deformable bodies are used, which change their overall shape every time step of the simulation. We propose and evaluate suitable bounding volume trees for deforming bodies that can be pre-built and then updated very efficiently during simulation. Several heuristics for updating the trees due to deformations are compared to each other. By combining a top-down and a bottom-up update strategy into a hybrid tree update method, promising results were achieved. Experiments show that our approach is four to five times faster than a previously leading method.
3dml: A Language for 3D Interaction Techniques
(Eurographics Association, 2001) Figueroa, Pablo; Green, Mark; Hoover, H. James
We present 3dml, a markup language for 3D interaction techniques and virtual environment applications that involve non-traditional devices. 3dml has two main purposes: readability and rapid development. Designers can read 3dml-based representations of 3D interaction techniques, compare them, and understand them. 3dml can also be used as a front end for any VR toolkit, so designerswithout programming skills can create VR applications as 3dml documents that plug together interaction techniques, VR objects, and devices. This paper focuses on the language features and presentation scheme designed in our website (http://www.cs.ualberta.ca/~pfiguero/3dml).
Constructive Hypervolume Textures
(Eurographics Association, 2001) Schmitt, B.; Pasko, A.; Adzhiev, V.; Schlick, C.
The concept of solid texturing is extended in two directions: constructive modeling of space partitions for texturing and modeling of multidimensional textured objects called hypervolumes. A hypervolume is considered as a point set with attributes of both physical (density, temperature, etc.) and photometric (color, transparency, diffuse and specular reflections, etc.) nature. The point set geometry and attributes are modeled independently using real-valued scalar functions of several variables. Each real-valued function defining geometry or an attribute is evaluated in the given point by a procedure traversing a constructive tree structure with primitives in the leaves and operations in the nodes of the tree. This approach provides a framework for modeling, texturing and visualization of 3D solids, time- dependent and multidimensional objects in a completely uniform manner. We introduced a special modeling language and implemented software tools supporting the proposed approach. The concept of constructive hypervolume textures is independent of the geometry representation. We provide examples of textured Frep and BRep objects as illustrations.
Data Mining and Visualization of High Dimensional Datasets
(Eurographics Association, 2001) Inselberg, Alfred
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Redirected Walking
(Eurographics Association, 2001) Razzaque, Sharif; Kohn, Zachariah; Whitton, Mary C.
Redirected Walking, a new interactive locomotion technique for virtual environments (VEs), captures the benefits of real walking while extending the possible size of the VE. Real walking, although natural and producing a high subjective sense of presence, limits virtual environments to the size of the tracked space. Redirected Walking addresses this limitation by interactively and imperceptibly rotating the virtual scene about the user. The rotation causes the user to walk continually toward the furthest wall of the lab without noticing the rotation. We implemented the technique using stereo graphics and 3D spatialized audio. Observations during a pilot study suggest that the technique works: Redirected Walking causes people to change their real walking direction without noticing it, allows for larger VEs, and does not induce appreciable simulator sickness.
Animating cuts with on-the-fly re-meshing
(Eurographics Association, 2001) Ganovelli, Fabio; O’Sullivan, C.
The problem of defining a model for deformable objects which allows the user to perform cuts is still open. Generally speaking, the reason is that such a task affects the connectivity and the topology of the mesh, while the assumption that they never change is the basis of most algorithms for both computation of deformation and collision detection. The drawback of approaching this problem as one of cutting based on re-meshing, is that the mesh exhibits a higher density where it has been cut than elsewhere. This paper proposes an on-the-fly tetrahedral simplification scheme to cope with such a fragmentation problem.
Inhabited Virtual Heritage
(Eurographics Association, 2001) Magnenat-Thalmann, Nadia; Chalmers, Alan; Thalmann, Daniel
Two techniques depending on the interest – accuracy and precision of the obtained object model shapes, • CAD systems, medical application. – visual realism and speed for animation of the reconstructed models, • internet applications • Virtual Reality applications.
Animation of Facial Expressions by Physical Modeling
(Eurographics Association, 2001) Zhang, Yu; Prakash, Edmond C.; Sung, Eric
In this paper, we propose a physically-based 3D dynamic facial model based on anatomical knowledge for realistic facial expression animation. The facial model incorporates a physically-based approximation to facial skin tissue and a set of anatomically-motivated facial muscle actuators. The tissue model has multilayered mass-spring structure which approximates different types of facial tissue. Two kinds of biphasic springs, structural springs and shear springs, are included in our model to simulate nonlinear elastic behavior of the skin. Facial muscle models are presented to emulate facial muscle contraction. In the muscle model, two factors, the muscle force scaling factor and muscle strength factor provide us macro and micro control of the muscle influence respectively. Based on the facial anatomy, these contractile muscles are inserted at anatomically correct position within the dynamic skin model. Lagrangian mechanics governs the dynamics, dictating the deformation of facial surface in response to muscle forces. The dynamic facial animation algorithm runs at interactive rate with continuous 3D display on a graphics workstation.
Rendering and Visualization in Parallel Environments
(Eurographics Association, 2001) Bartz, Dirk; Silva, Claudio
The continuing commoditization of the computer market has precipitated a qualitative change. Increasingly powerful processors, large memories, big harddisk, high-speed networks, and fast 3D rendering hardware are now affordable without a large capital outlay. Clusters of workstations and SMP-servers are utilizing these technologies to drive interactive applications like large graphical display walls (i.e., Powerwall or CAVE systems). In this tutorial, attendees will learn how to understand and leverage (technical and personal) workstation- and serverbased systems as components for parallel rendering. The goal of the tutorial is twofold: Attendees will thoroughly understand the important characteristics workstations architectures. We will present an overview of different workstation (Intel-based and others) and server architectures (including graphics hardware), addressing both single-processors as well as SMP architectures. We will also introduce important methods of programming in parallel environment with special attention how such techniques apply to developing cluster-based parallel renderers. Attendees will learn about different approaches to implement parallel renderers. The tutorial will cover parallel polygon and volume rendering. We will explain the underlying concepts of workload characterization, workload partitioning, and static, dynamic, and adaptive load balancing. We will then apply these concepts to characterize various parallelization strategies reported in the literature for polygon and volume rendering. We abstract from the actual implementation of these strategies and instead focus on a comparison of their benefits and drawbacks. Case studies will provide additional material to explain the use of these techniques. The tutorial will be structured into three main sections: We will first discuss the fundamentals of parallel programming and parallel machine architectures. Topics include message passing vs. shared memory, thread programming, a review of different SMP architectures, clustering techniques, PC architectures for personal workstations, and graphics hardware architectures. The second section builds on this foundation to describe key concepts and particular algorithms for parallel polygon and volume rendering. These concepts are supplemented with concrete parallel rendering implementations

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