EG2001

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Rendering: Input and Output
(Eurographics Association, 2001) Rushmeier, Holly
Rendering is the process of creating an image from numerical input data. In the past few years our ideas about methods for acquiring the input data and the form of the output have expanded. The availability of inexpensive cameras and scanners has influenced how we can obtain data needed for rendering. Input for rendering ranges from sets of images to complex geometric descriptions with detailed BRDF data. The images that are rendered may be simply arrays of RGB images, or they may be arrays with vectors or matrices of data defined for each pixel. The rendered images may not be intended for direct display, but may be textures for geometries that are to be transmitted to be rendered on another system. A broader range of parameters now need to be taken into account to render images that are perceptually consistent across displays that range from CAVEs to personal digital assistants. This presentation will give an overview of how new hardware and new applications have changed traditional ideas of rendering input and output.
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.
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?
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.
Improved Rendering with Dégradé
(Eurographics Association, 2001) Boyer, Vincent; Sobczyk, Dominique; Bourdin, Jean-Jacques
In most paintboxes drawing (and filling) the picture and render the picture are two different steps and tools. Dégradé presents an efficient filling rendering tool: an efficient collection of effect filling. In Dégradé the renderer is included in the drawing process. This method enhance the renderer possibilities and the graphic designer work.
Occlusion Culling Methods
(Eurographics Association, 2001) Hey, Heinrich; Purgathofer, Werner
Web 2D Graphics: State-of-the-Art
(Eurographics Association, 2001) Duce, David; Herman, Ivan; Hopgood, Bob
The early browsers for the Web were predominantly aimed at retrieval of textual information. Tim Berners-Lee's original browser for the NeXT computer did allow images to be viewed but they popped up in a separate window and were not an integral part of the Web page. In January 1993, the Mosaic browser was released by NCSA. The browser was simple to download and, by the Autumn of 1993, was available for X workstations, PCs and the Mac. From 50 Web servers at the start of 1993, Web traffic had risen to 1% of internet traffic by October and 2.5% by the end of the year. About a million downloads of the Mosaic browser took place that year. In February of 1993, Mark Andreessen proposed the element as an extension to Mosaic's HTML to provide a way of adding images to Web pages. In 1994, Dave Raggett developed an X-browser that allowed text to flow around images and tables and from then on images were an accepted part of the Web page. Web pages became glossier and the enormous growth of the Web started [1] [2]. Organisations could customise their home pages with the company logo. Maps, albeit images, could be added to show how to reach the organisation. Its products could be displayed on the Web. Eventually, the Web would become a major commercial outlet.
Gaze-Contingent Level Of Detail Rendering
(Eurographics Association, 2001) Murphy, Hunter; Duchowski, Andrew T.
The contributions of this paper are the development and evaluation of a nonisotropic model-based Level Of Detail (LOD) rendering technique for gaze-contingent viewing of multiresolution meshes. A high resolution portion of the model is rendered at the eye-tracked Point Of Regard (POR). A method is given for converting a closed polygonal mesh to a nonisotropic LOD representation suitable for gaze-contingent viewing. Based on a theoretical model of visual acuity, a three-dimensional spatial degradation function is obtained from human subject experiments in an attempt to render imperceptibly degraded geometric objects. Unlike previous LOD approaches, our resolution degradation method is based on the measurement of visual angle in world coordinates and is applied directly to object geometries prior to rendering. The gaze-contingent technique is evaluated in a Virtual Reality (VR) system integrated with a binocular eye tracker. To our knowledge, this is the first example of a binocular eye-tracked VR system used to evaluate a gaze-contingent modeling technique. Results are reported in terms of rendering performance, indicating an overall 4-fold average frame rate improvement during gaze-contingent viewing. Frame rate improvement ranged from a factor of at least 2, up to a 15-fold gain in performance over full resolution display, varying with the model complexity and the instantaneous direction of the viewer’s gaze.
A Simple Validity Condition for B-Spline Hyperpatches
(Eurographics Association, 2001) Conde Rodriguez, Francisco de Asis; Torres Cantero, Juan Carlos
The use of hyperpatches as a method for solid modelling has a problem: the validity of the model is not guaranteed. The problem of ensuring the validity of hyperpatch representations of solids is discussed in this work, and a validity condition for cubic uniform b-spline hyperpatches is presented. Our validity condition is based on comparisons among points, and it is robust and easy to implement.
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.
N-Adic Subdivision Schemes for Local Mesh Deformation
(Eurographics Association, 2001) Salomon, Gabriel; Leclerq, Antoine; Akkouche, Samir; Galin, E.
This paper presents an interpolating subdivision scheme based on an N-adic decomposition of the parameter space. This approach enables us to locally deform the surface according to a modification of the normals at the vertices of the control mesh. Experiments show that the N-adic decomposition provides a better control over the deformations, whereas a dyadic decomposition method often produces smoother surfaces.
Approximated View Reconstruction Using Precomputed ID-Bitfields
(Eurographics Association, 2001) Meruvia Pastor, Oscar E.; Strothotte, Thomas
A technique is presented to construct arbitrary views of a model by using previously computed views. The technique is simple to implement, completely general for polygonal models and can be used within object hierarchies or scene graphs. During a preprocessing step images of a model are taken from different viewpoints. These images are saved using long bitfields (ID-bitfields) which encode the visibility information according to an array of the model’s primitives used as the base for the bitfield. These ID-bitfield encodings, together with the primitive array, are then used by a viewer which selects and joins them to provide an approximated (not conservative) reconstruction of the visible elements of the object for a new viewpoint. The technique implicitly performs occlusion culling, since a minimal set of visible polygons is the result of the reconstruction. Results show how interaction can be improved when working with high depth complexity models. Satisfactory reconstructions are achieved by taking as few as 25 images around an object. This paper suggests how the technique can be extended to other applications such as virtual walkthroughs and visualization of non-realistic images, and how graphics libraries and hardware could be enhanced by allowing the application to pass an ID-bitfield. Key words: view reconstruction, interactive display, visibility preprocessing, occlusion culling, polygon reduction.
Warped Textures for UV Mapping Encoding
(Eurographics Association, 2001) Sorkine, Olga; Cohen-Or, Daniel
This paper introduces an implicit representation of the u; v texture mapping. Instead of using the traditional explicit u; v mapping coordinates, a non-distorted piecewise embedding of the triangular mesh is created, on which the original texture is remapped, yielding warped textures. This creates an effective atlas of the mapped triangles and provides a compact encoding of the texture mapping.
Virtual Actors’ Behaviour for 3D Interactive Storytelling
(Eurographics Association, 2001) Cavazza, Marc; Charles, Fred; Mead, Steven J.; Strachan, Alexander I.
In this paper, we describe a method for implementing intelligent behaviour for artificial actors in the context of interactive storytelling. We have developed a fully implemented prototype based on the Unreal™ game engine and carried experiments with a simple sitcom-like scenario. We discuss the central role of artificial actors in interactive storytelling and how real-time generation of their behaviour participates to the creation of a dynamic storyline. We follow previous work describing the behaviour of artificial actors through AI planning formalisms, and adopt a search-based approach to planning. The set of all possible behaviours, accounting for many different instantiations of a basic plot, can be represented through an AND/OR graph. Under certain formal conditions, the solution plan can be obtained by directly searching the graph with the AO* algorithm. We describe our implementation of AO* and how it addresses the specific issues of 3D interactive storytelling, such as interaction with the virtual world and user intervention.
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 driven motion transitions for interactive games
(Eurographics Association, 2001) Mizuguchi, Mark; Buchanan, John; Calvert, Tom
In 3D video games that employ human characters, a series of animations is required to display a character’s motion. The current approach is to use stored animation sequences, either motion captured or hand animated, and play them back as required. Unlike a sequence for film or video the motion needs to change according to the user’s interaction with the game. There are constant unpredictable transitions from one animation into another. This paper presents the design and analysis of a framework for supporting data driven transitions that have been pre-specified by animators. This approach frees the programmers from having to determine the details of each transition and gives control to the animators. This takes advantage of the animators’ skill at evaluating and tweaking the motion to produce better aesthetic results and lets the animators and programmers work in parallel.
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.
Interactive Simulation for Multimodal Virtual Environments
(Eurographics Association, 2001) Pai, Dinesh K.
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An On-line Occlusio-Culling Algorithm for FastWalkthrough in Urban Areas
(Eurographics Association, 2001) Wang, Yusu; Agarwal, Pankaj K.; Har-Peled, Sariel
We describe a fast algorithm to speed up rendering of scenes for walkthroughs in urban environments. Our occlusion culling algorithm takes advantage of temporal coherence in image space. As such, occlusion calculation is performed online only when needed. This enables us to employ intelligent occluder-selection and culling algorithms. We do not preprocess visibility information or pre-select occluders. Therefore, we can update scenes dynamically at a little cost. The algorithm features a tradeoff between accuracy and efficiency. While it approximates visibility testing, our experiments show that errors occur rarely.
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.

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