EG2001

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

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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?
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.
Piecewise Constant Conic Sections for Accelerated Volume Density Rendering
(Eurographics Association, 2001) Hougs, Roland B.; Day, A. M.
In order to accelerate the rendering of volumetric shadows, we propose a new technique which builds sets of conic volumes to approximate the shape of shadows in a participating medium. The novelty of our approach is notably the construction of the cone-sets, which are built with no knowledge of the underlying geometry of the scene. Instead, information collected during the construction of a global photon map is used to derive an estimate of the outline of the shadows in three dimensions. This information is then used in several different ways to speed up the rendering pass. The method shares many of the advantages proposed by photon maps such as viewpoint independence and decoupling from the geometry of the scene.
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
A Visualization System for the Clinical Evaluation of Cerebral Aneurysms from MRA Data
(Eurographics Association, 2001) Perrin, James S.; Lacey, A.; Laitt, R.; Jackson, A.; John, Nigel W.
This paper details a work-in-progress application under development as part of a clinical visualization project. The software has been designed to meet the specific needs of interventional neuro-radiologists evaluating the suitability of intracranial aneurysms for endovascular coiling and also when planning the procedure. Providing rapid (real-time) interaction with high resolution iso-surfaces derived from Time-of Flight (ToF) Magnetic Resonance Angiography (MRA) data will enable the clinician to quickly assess the ability of the aneurysm to accept a coil, with greater reliability than exisiting, 2D film techniques. Simulating the interface of the C-arm angiography system, used during the procedure, allows the clinician to evaluate various surgical strategies, potentially reducing procedure times and therefore patient radiation dosage. The first release of the software is currently under-going clinical evaluation.
Free-Form Deformation of Solid Models in CSR
(Eurographics Association, 2001) Hui, K. C.; Lai, C.F.
Existing free-form deformation (FFD) techniques deform an object by deforming the space enclosing the object. Points on the object are thus deformed relative to the undeformed space (or world space). The deformed object is visualized by sampling points on the object surfaces, or by approximating the object with a polyhedral model. This provides good visual effect for the deformed objects. However, the deformed solid is represented in terms of the lattice of the FFD and the undeformed solid. There is no precise explicit representation of the deformed object so that existing solid modeling techniques, such as Boolean operations, on the deformed object may not be applied. This paper is concerned with the techniques of applying free-form deformation on solid models represented by the Constructive Shell Representation (CSR). By applying free-form deformation on the surface points of the trunctets of a CSR object so that the vertices and the quadric patch polynomial of the trunctets are changed, the shape of the object can be modified. This technique can be used to deform globally smooth solid models or general solid models with sharp edges. The deformation can be applied either globally or locally. Techniques for the deformation are discussed in detail. Experiments are conducted and the results are also presented.
CORBA Visualization Platform
(Eurographics Association, 2001) Benoist, Thierry; Hewitt, W. T.; John, Nigel W.
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Parametric Motion Blending through Wavelet Analysis
(Eurographics Association, 2001) Ahmed, Amr; Mokhtarian, Farzin; Hilton, Adrian
This paper shows how multiresolution blending can be employed with time-warping for realistic parametric motion generation from pre-stored motion data. The goal is to allow the animator to define the desired motion using its natural parameters such as speed. Generation of a realistic motion is achieved using pre-stored captured animations. Analysis has been carried out to investigate the relationship between the walking speed and blending factor to remove the burden of trial and errors from the animator. As a result, realistic walking motion with the speed specified by the user can be generated. This desired speed should be between the minimum and maximum speeds of the available motion data. Analysis to generalise these results to other motions are in progress. Generating the desired motion for different scaled avatars is also discussed.
Complexity Reduction of Catmull-Clark/Loop Subdivision Surfaces
(Eurographics Association, 2001) Steenberg, Eskil
By applying a filter this algorithm can reduce the number of polygons generated by subdividing a mesh dynamically. This algorithm is designed especially for real-time engines where the geometrical complexity is critical. It also avoids edge cracks and is generally more efficient than a general-purpose polygon reduction algorithm.
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.
Mesh Morphing
(Eurographics Association, 2001) Alexa, Marc
Meshes have become a widespread and popular representation of models in computer graphics. Morphing techniques aim at transforming a given source shape into a target shape. Morphing techniques have various applications ranging from special effects in television and movies to medical imaging and scientific visualization. Not surprisingly, morphing techniques for meshes have received a lot of interest lately. This state of the art report sums up recent developments in the area of mesh morphing. It presents a consistent framework to classify and compare various techniques approaching the same underlying problems from different angles.
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.
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).
Approximated Phong Shading by using the Euler Method
(Eurographics Association, 2001) Hast, Anders; Barrera, Tony; Bengtsson, Ewert
After almost three decades and several improvements, Gouraud shading is still more often used for interactive computer graphics than Phong shading. One of the main reasons for this is of course that Phong shading is computationally more expensive. Quadratic polynomial approximation techniques like Bishop’s method could reduce the amount of computation in the inner loop to just the double of what is done in Gouraud shading. By using Euler’s method we get another quadratic polynomial approximation technique which is just as fast in the inner loop, but it will also give correct intensities on the edges, which we will not get with Bishop’s method. By computing the maximum difference over a scan line between Gouraud shading and the proposed method, we could decide if Gouraud will suffice. It is also shown that linearly interpolated normals are normalized by a symmetric function. This means that we could reduce the amount of square roots by the half in Phong shading.
Scalable Impressionist Rendering
(Eurographics Association, 2001) Atencia, A.; Bourdin, Jean-Jacques; Boyer, V.; Pissard, T.; Sobczyk, D.
The painted impressionist technique produces scale based effects: the far range vision is almost realistic while the close vision is blurred. In NPR, Impressionist Renderers are mainly based on a medium range vision. A very accurate scalable impressionist effect has been implemented and improves both close and far range vision.
Interactive 3D Modeling in the Inception Phase of Architectural Design
(Eurographics Association, 2001) de Vries, B.; Jessurun, A.J.; van Wijk, J.J.
In architectural design 3D modeling in the inception phase is up to now not supported in CAD. Moreover 3D modeling is still far from intuitive with the common interface techniques. This paper introduces a 3D modeling tool for architects, which is limited in its purposes but yet very powerful in its use. A cube is the basic drawing element to construct building masses. Modification of the design is achieved by dragging sets of cubes resulting in the creation or deletion of new cubes.
Post-rendering Composition for 3D Scenes
(Eurographics Association, 2001) Grimm, Cindy
In traditional art a painter displays a 3D scene on a 2D image plane in a manner that is aesthetically pleasing. The arrangement of objects and colors is called composition and is the subject of many art books and classes. While a painter may use perspective to create depth in a scene they may also alter the perspective and color, either subtly or dramatically, to influence the focus of viewer and the effect of the image. To date, traditional 3D graphics packages have largely concentrated on modeling, textures, and lighting to create images and provide few tools for altering the composition post-rendering. In this paper we present several simple techniques for creating images with non-standard perspective and color using standard 3D rendering packages. The scene is modeled in 3D but each object has its own camera, color balance, and image size, allowing the user to alter the composition after the 3D rendering step. The purpose of this paper is not to present a complete composition system but rather to illustrate the potential of compositionbased tools.
Automatic Animated Face Modeling Using Multiview Video
(Eurographics Association, 2001) Wu, Fu-Che; Murphy, Chien-Chang Ho; Ouhyoung, Ming
An image-based 3-D modeling system is presented in this paper. Our modeling system consists of three main stages: camera calibration, depth estimation and 3-D geometry reconstruction. All of these steps are executed automatically. In the camera calibration stage, some patterns are used that help to determine the camera’s position in an environment. The camera’s intrinsic and external parameters are determined using epipolar geometry. After the camera parameters are determined, the camera’s location in each projected frame is determined. The depth for each pixel in a base image is estimated from the camera’s focus to the object’s surface by measuring the similarity between the base image and the neighboring images. The object’s 3-D geometry is reconstructed with texture from the base image using the depth information.
Space-Time Hierarchical Radiosity with Clustering and Higher-OrderWavelets
(Eurographics Association, 2001) Damez, Cyrille; Holzschuch, Nicolas; Sillion, Francois X.
We address in this paper the issue of computing global illumination solutions for animation sequences. The principal difficulties lie in the computational complexity of global illumination, emphasized by the movement of objects and the large number of frames to compute, as well as the potential for creating temporal discontinuities in the illumination, a particularly dangerous and noticeable artifact. We demonstrate how space-time hierarchical radiosity, i.e. the application to the time dimension of a hierarchical decomposition algorithm, can be effectively used to obtain smooth animations: first by proposing the integration of spatial clustering in a space-time hierarchy; second, by changing the wavelet basis used for the temporal dimension. The resulting algorithm is capable of creating time-dependent radiosity solutions efficiently.

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