Volume 20 (2001)

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Real-Time Cloud Rendering
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Harris, Mark J.; Lastra, Anselmo
This paper presents a method for realistic real-time rendering of clouds suitable for flight simulation and games. It provides a cloud shading algorithm that approximates multiple forward scattering in a preprocess, and first order anisotropic scattering at runtime. Impostors are used to accelerate cloud rendering by exploiting frame-to-frame coherence in an interactive flight simulation. Impostors are shown to be particularly well suited to clouds, even in circumstances under which they cannot be applied to the rendering of polygonal geometry. The method allows hundreds of clouds and hundreds of thousands of particles to be rendered at high frame rates, and improves interaction with clouds by reducing artifacts introduced by direct particle rendering techniques.
Interactive Display of Global Illumination Solutions for Non-diffuse Environments - A Survey
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Heidrich, Wolfgang
In recent years there has been a lot of work on interactively displaying global illumination solutions for non-diffuse environments. This is an extremely active field of research, in which a lot of different approaches have recently been proposed. In this survey, we will discuss and compare these. This will hopefully prepare the ground for systematically addressing the open questions in the future.
Rendering Pearlescent Appearance Based On Paint-Composition Modelling
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Ershov, Sergey; Kolchin, Konstantin; Myszkowski, Karol
We describe a new approach to modelling pearlescent paints based on decomposing paint layers into stacks of imaginary thin sublayers. The sublayers are chosen so thin that multiple scattering can be considered across different sublayers, while it can be neglected within each of the sublayers. Based on this assumption, an efficient recursive procedure of assembling the layers is developed, which enables to compute the paint BRDF at interactive speeds. Since the proposed paint model connects fundamental optical properties of multi-layer pearlescent and metallic paints with their microscopic structure, interactive prediction of the paint appearance based on its composition becomes possible.
Eurographics
(Blackwell Publishers Ltd and the Eurographics Association., 2001)
Haptic Device Control - Will it Fit Standardized Input Models?
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Arnold, D. B.; Day, A. M.; Jennings, V.; Courtenay, A.; Duce, D. A.
Over recent years a wide variety of interaction devices involving haptic feedback have been brought to the market, but they vary widely in terms of input measures recorded. These range from one dimensional input on a haptic feedback steering wheel to a six degree of freedom position and orientation device and further, to assemblies of such devices. On the surface most of the variations can be accommodated logically with standardized input models combining existing logical input devices and haptic feedback processes as acknowledgement/echos. However it is very uncertain whether such a model can adequately model the system requirements for effective haptic feedback.In this paper we review the input models that have developed over the past 20 years and ask "Is it the end of the road for the conceptual model of input incorporated into the early graphics standards and elaborated over the years?" In addition, to highlight the problems of implementation with haptic interaction, we describe a typical application, the simulation of a collision with a virtual wall.
Walk-Through Illustrations: Frame-Coherent Pen-and-Ink Style in a Game Engine
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Freudenberg, Bert; Masuch, Maic; Strothotte, Thomas
In this paper we show how a game engine designed to generate photorealistic images can be extended to produce non-photorealistic and hybrid renditions. We introduce new hardware-based methods to accomplish pen-and-ink illustrations. The combination of the highly optimized processing of a game engine and the use of hardware for NPR algorithms yields real-time animation of pen-and-ink illustrations.The particular advance of this method is that it yields the first real-time, frame-coherent pen-and-ink animations which maintain both tone and texture.
Visibility Driven Rasterization
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Meissner, M.; Bartz, D.; Gunther, R.; Strasser, W.
We present a new visibility driven rasterization scheme that significantly increases the rendering performance of modern graphic subsystems. Instead of rasterizing, texturing, lighting, and depth-testing each individual pixel, we introduce a two-level visibility mask within the rasterization stage which facilitates the removal of groups of pixels and triangles from rasterization and subsequent pipeline stages.Local visibility information is stored within the visibility mask that is updated several times during the generation of a frame. The update can easily be accomplished by extending already available (in hardware) occlusion culling mechanisms (i.e. those of HP and SGI), where it is possible to integrate the additional functionality without any additional delay cycles. In addition to these existing hardware based occlusion culling approaches-which cull only geometry contained in bounding volumes determined as occluded-we are able to significantly accelerate the rendering of the geometry determined as visible. However, our approach does not specifically rely on such occlusion culling hardware.The proposed new rasterization scheme is well suited for hardware implementation, can easily be integrated into low-cost rasterizers, and its scalability can vary upon available chip real estate. Only incremental modifications of modern graphics subsystems are required to achieve a significant improvement in rendering performance.
A Novel Approach for Delaunay 3D Reconstruction with a Comparative Analysis in the Light of Applications
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Nonato, L.; Minghim, R.; Oliveira, M. C. F.; Tavares, G.
This paper presents a novel algorithm for volumetric reconstruction of objects from planar sections using Delaunay triangulation, which solves the main problems posed to models defined by reconstruction, particularly from the viewpoint of producing meshes that are suitable for interaction and simulation tasks. The requirements for these applications are discussed here and the results of the method are presented. Additionally, it is compared to another commonly used reconstruction algorithm based on Delaunay triangulation, showing the advantages of the reconstructions obtained by our technique.
Multiresolution for Algebraic Curves and Surfaces using Wavelets
(Blackwell Publishers Ltd and the Eurographics Association., 2001) Esteve, Jordi; Brunet, Pere; Vinacua, Alvar
This paper describes a multiresolution method for implicit curves and surfaces. The method is based on wavelets, and is able to simplify the topology. The implicit curves and surfaces are defined as the zero-valued piece-wise algebraic isosurface of a tensor-product uniform cubic B-spline. A wavelet multiresolution method that deals with uniform cubic B-splines on bounded domains is proposed. In order to handle arbitrary domains the proposed algorithm dynamically adds appropriate control points and deletes them in the synthesis phase.
Modeling Dynamic Hair as a Continuum
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Hadap, Sunil; Magnenat-Thalmann, Nadia
In this paper we address the difficult problem of hair dynamics, particularly hair-hair and hair-air interactions. To model these interactions, we propose to consider hair volume as a continuum. Subsequently, we treat the interaction dynamics to be fluid dynamics. This proves to be a strong as well as viable approach for an otherwise very complex phenomenon. However, we retain the individual character of hair, which is vital to visually realistic rendering of hair animation. For that, we develop an elaborate model for stiffness and inertial dynamics of individual hair strand. Being a reduced coordinate formulation, the stiffness dynamics is numerically stable and fast. We then unify the continuum interaction dynamics and the individual hair's stiffness dynamics.
Interactive Computer Animation of Hand Gestures using Status Estimation with Multiple Regression Analysis
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Kitamura, Yoshifumi; Higashi, Tomohiko; Iida, Takayuki; Kishino, Fumio
This paper presents a method of interactively generating natural hand gesture animation using reduced dimensionality from multiple captured data sequences of finger motions conducting specific tasks. This method is achieved by introducing an estimation with multiple regression analysis. Even when the skeletal structure of the user who inputs the motion is different from that of the shape model in the computer, the motion that a user imagines is generated. Experimental results obtained from the interface applied to virtual object manipulation showed that the proposed method generates animation naturally, just as users would expect. This method enables us to make input devices that require minimal user training and computer calibration, and helps to make the user interface intuitive and easy to use.
Tour Into the Picture using a Vanishing Line and its Extension to Panoramic Images
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Kang, Hyung Woo; Pyo, Soon Hyoung; Anjyo, Ken-ichi; Shin, Sung Yong
Tour into the picture (TIP) proposed by Horry et al.13 is a method for generating a sequence of walk-through images from a single reference picture (or image). By navigating a 3D scene model constructed from the picture, TIP produces convincing 3D effects. Assuming that the picture has one vanishing point, they proposed the scene modeling scheme called spidery mesh. However, this scheme has to go through major modification when the picture contains multiple vanishing points or does not have any well-defined vanishing point. Moreover, the spidery mesh is hard to generalize for other types of images such as panoramic images. In this paper, we propose a new scheme for TIP which is based on a single vanishing line instead of a vanishing point. Based on projective geometry, our scheme is simple and yet general enough to address the problems faced with the previous method. We also show that our scheme can be naturally extended to a panoramic image.
3D Metamorphosis Between Different Types of Geometric Models
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Breen, David E.; Mauch, Sean; Whitaker, Ross T.; Mao, Jia
We present a powerful morphing technique based on level set methods, that can be combined with a variety of scan conversion/model processing techniques. Bringing these techniques together creates a general morphing approach that allows a user to morph a number of geometric model types in a single animation. We have developed techniques for converting several types of geometric models (polygonal meshes, CSG models and MRI scans) into distance volumes, the volumetric representation required by our level set morphing approach. The combination of these two capabilities allows a user to create a morphing sequence regardless of the model type of the source and target objects, freeing him/her to use whatever model type is appropriate for a particular animation.
Adaptive Implicit Surface Polygonization Using Marching Triangles
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Akkouche, Samir; Galin, Eric
This paper presents several improvements to the marching triangles algorithm for general implicit surfaces. The original method generates equilateral triangles of constant size almost everywhere on the surface. We present several modifications to adapt the size of the triangles to the curvature of the surface. As cracks may arise in the resulting polygonization, we propose a specific crack-closing method invoked at the end of the mesh growing step. Eventually, we show that the marching triangles can be used as an incremental meshing technique in an interactive modeling environment. In contrast to existing incremental techniques based on spatial subdvision, no extra data-structure is needed to incrementally edit skeletal implicit surfaces, which saves both memory and computation time.
Implementation and Complexity of the Watershed-from-Markers Algorithm Computed as a Minimal Cost Forest
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Felkel, Petr; Bruckschwaiger, Mario; Wegenkittl, Rainer
Displacement Mapping using Scan Conversion Hardware Architectures
(Blackwell Publishers Ltd and the Eurographics Association., 2001) Doggett, Michael; Kugler, Anders; Strasser, Wolfgang
This paper presents a novel algorithm and architectures for perspective correct displacement of the surface geometry of a polygonal model using a displacement map. This new displaced surface geometry is passed onto a traditional rendering pipeline. The algorithm uses a multiple pass approach in which the geometry is displaced in the first pass and then the displaced geometry is rendered. The significant features of the algorithm are that the surface is displaced after its triangle mesh is transformed into screen space and that it uses only bi-linear interpolation for calculating the displaced geometry allowing a cheap incremental scan-line implementation. A hardware architecture based on this algorithm is presented along with possible alternative implementations. The technique presented here allows greater photorealism by using increased detail without an increase in bandwidth for geometry or calculation time for transformation.
Rendering: Input and Output
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Rushmeier, H.
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.
A Unified Subdivision Scheme for Polygonal Modeling
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Maillot, Jerome; Stam, Jos
Subdivision rules have traditionally been designed to generate smooth surfaces from polygonal meshes. In this paper we propose to employ subdivision rules as a polygonal modeling tool, specifically to add additional level of detail to meshes. However, existing subdivision schemes have several undesirable properties making them ill suited for polygonal modeling. In this paper we propose a general set of subdivision rules which provides users with more control over the subdivision process. Most existing subdivision schemes are special cases. In particular, we provide subdivision rules which blend approximating spline based schemes with interpolatory ones. Also, we generalize subdivision to allow any number of refinements to be performed in a single step.
Tensor Topology Tracking: A Visualization Method for Time-Dependent 2D Symmetric Tensor Fields
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Tricoche, X.; Scheuermann, G.; Hagen, H.
Topological methods produce simple and meaningful depictions of symmetric, second order two-dimensional tensor fields. Extending previous work dealing with vector fields, we propose here a scheme for the visualization of time-dependent tensor fields. Basic notions of unsteady tensor topology are discussed. Topological changes - known as bifurcations - are precisely detected and identified by our method which permits an accurate tracking of degenerate points and related structures.
Rendering Natural Waters
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Premoze, Simon; Ashikhmin, Michael
Creating and rendering realistic water is one of the most daunting tasks in computer graphics. Realistic rendering of water requires that the sunlight and skylight illumination are correct, the water surface is modeled accurately and that the light transport within water body is properly handled. This paper describes a method for wave generation on a water surface using a physically-based approach. The wave generation uses data from the oceanographical observations and it is controlled by intuitive parameters such as wind speed and wind direction. The optical behavior of the water surfaces is complex but is well-described in the ocean science literature. We present a simple and intuitive light transport approach that is easy to use for many different water types such as deep ocean water, muddy coastal water, and fresh water bodies. We demonstrate our model for a number of water and atmospheric conditions.

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