27-Issue 8

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https://diglib.eg.org/handle/10.2312/141

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2008 Eurographics Symposium on Parallel Graphics and Visualization
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Weiskopf, Daniel
Adaptive Surface Texture Synthesis Using Round-Shaped Neighbourhoods
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Chen, D.; Dong, F.
This paper presents a novel surface texture synthesis method, which is capable of producing high-quality results by performing the synthesis within an effective multi-resolution scheme using an adaptive texture similarity metric. Compared with related works, our method allows us to directly carry out multi-resolution synthesis without involving complicated operations such as mesh hierarchy and partitioning on the target surface. Also, the adaptive similarity metric focuses on measuring texture properties at different scales ranging from local to global, allowing for consistency within differently-sized texture structures. Further, with the introduced round shaped neighbourhoods, we can save considerable amount of computation for the surface texture synthesis over variable texture directions. Experimental results are provided and comparisons are made against other latest works.
Book Review
(The Eurographics Association and Blackwell Publishing Ltd, 2008)
Camera Control in Computer Graphics
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Christie, Marc; Olivier, Patrick; Normand, Jean-Marie
Recent progress in modelling, animation and rendering means that rich, high fidelity virtual worlds are found in many interactive graphics applications. However, the viewer s experience of a 3D world is dependent on the nature of the virtual cinematography, in particular, the camera position, orientation and motion in relation to the elements of the scene and the action. Camera control encompasses viewpoint computation, motion planning and editing. We present a range of computer graphics applications and draw on insights from cinematographic practice in identifying their different requirements with regard to camera control. The nature of the camera control problem varies depending on these requirements, which range from augmented manual control (semi-automatic) in interactive applications, to fully automated approaches. We review the full range of solution techniques from constraint-based to optimization-based approaches, and conclude with an examination of occlusion management and expressiveness in the context of declarative approaches to camera control.
Compression and Importance Sampling of Near-Field Light Sources
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Mas, Albert; Martin, Ignacio; Patow, Gustavo
This paper presents a method for compressing measured datasets of the near-field emission of physical light sources (represented by raysets). We create a mesh on the bounding surface of the light source that stores illumination information. The mesh is augmented with information about directional distribution and energy density. We have developed a new approach to smoothly generate random samples on the illumination distribution represented by the mesh, and to efficiently handle importance sampling of points and directions. We will show that our representation can compress a 10 million particle rayset into a mesh of a few hundred triangles. We also show that the error of this representation is low, even for very close objects.
Cultural Heritage As a Vehicle for Basic Research in Computing Science: Pasteur s Quadrant and a Use-Inspired Basic Research Agenda
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Arnold, David
Donald Stokes argued [Sto97] that for 50 years from the end of the Second World War to the end of the 20th century, there was an unhealthy taxonomy of research types which was formulated on a linear scale from pure to applied. The argument goes that the best research is only possible in environments which are free from contemplation of the potential uses to which results might be applied. In this paper, current research challenges in the application of ICTs to cultural heritage information are reviewed in order to consider where these applications-linked needs require solutions that will advance the understanding of computational principles and help to develop new basic understanding in computer science, including shape manipulation and other aspects of importance in computer graphics and virtual environments. The paper draws extensively on the recently published EPOCH research agenda [AG07] for illustrations of the types of research which are required for the Cultural Heritage sector and the relationship between these and basic research challenges in Computing Science.
Diffusion Based Photon Mapping
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Schjoeth, L.; Sporring, J.; Fogh Olsen, O.
Density estimation employed in multi-pass global illumination algorithms give cause to a trade-off problem between bias and noise. The problem is seen most evident as blurring of strong illumination features. In particular, this blurring erodes fine structures and sharp lines prominent in caustics. To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features, while eliminating noise. We demonstrate the applicability of our algorithm through a series of tests. In the tests, we evaluate the visual and computational performance of our algorithm comparing it to existing popular algorithms.
Expressive Speech Animation Synthesis with Phoneme-Level Controls
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Deng, Z.; Neumann, U.
This paper presents a novel data-driven expressive speech animation synthesis system with phoneme-level controls. This system is based on a pre-recorded facial motion capture database, where an actress was directed to recite a pre-designed corpus with four facial expressions (neutral, happiness, anger and sadness). Given new phoneme-aligned expressive speech and its emotion modifiers as inputs, a constrained dynamic programming algorithm is used to search for best-matched captured motion clips from the processed facial motion database by minimizing a cost function. Users optionally specify hard constraints (motion-node constraints for expressing phoneme utterances) and soft constraints (emotion modifiers) to guide this search process. We also introduce a phoneme-Isomap interface for visualizing and interacting phoneme clusters that are typically composed of thousands of facial motion capture frames. On top of this novel visualization interface, users can conveniently remove contaminated motion subsequences from a large facial motion dataset. Facial animation synthesis experiments and objective comparisons between synthesized facial motion and captured motion showed that this system is effective for producing realistic expressive speech animations.
Geometry Textures and Applications
(The Eurographics Association and Blackwell Publishing Ltd, 2008) De Toledo, Rodrigo; Wang, Bin; Levy, Bruno
Geometry textures are a novel geometric representation for surfaces based on height maps. The visualization is done through a graphics processing unit (GPU) ray casting algorithm applied to the whole object. At rendering time, the fine-scale details (mesostructures) are reconstructed preserving original quality. Visualizing surfaces with geometry textures allows a natural level-of-detail (LOD) behaviour. There are numerous applications that can benefit from the use of geometry textures. In this paper, besides a mesostructure visualization survey, we present geometry textures with three possible applications: rendering of solid models, geological surfaces visualization and surface smoothing.
GPU-Based Spherical Light Field Rendering with Per-Fragment Depth Correction
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Todt, S.; Rezk-Salama, C.; Kolb, A.; Kuhnert, K.-D.
Image-based rendering techniques are a powerful alternative to traditional polygon-based computer graphics. This paper presents a novel light field rendering technique which performs per-pixel depth correction of rays for high-quality reconstruction. Our technique stores combined RGB and depth values in a parabolic 2D texture for every light field sample acquired at discrete positions on a uniform spherical setup. Image synthesis is implemented on the GPU as a fragment program which extracts the correct image information from adjacent cameras for each fragment by applying per-pixel depth correction of rays.We show that the presented image-based rendering technique provides a significant improvement compared to previous approaches. We explain two different rendering implementations which make use of a uniform parametrisation to minimise disparity problems and ensure full six degrees of freedom for virtual view synthesis. While one rendering algorithm implements an iterative refinement approach for rendering light fields with per pixel depth correction, the other approach employs a raycaster, which provides superior rendering quality at moderate frame rates.GPU based per-fragment depth correction of rays, used in both implementations, helps reducing ghosting artifacts to a non-noticeable amount and provides a rendering technique that performs without exhaustive pre-processing for 3D object reconstruction and without real-time ray-object intersection calculations at rendering time.
High Performance GPU-based Proximity Queries using Distance Fields
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Morvan, T.; Reimers, M.; Samset, E.
Proximity queries such as closest point computation and collision detection have many applications in computer graphics, including computer animation, physics-based modelling, augmented and virtual reality. We present efficient algorithms for proximity queries between a closed rigid object and an arbitrary, possibly deformable, polygonal mesh. Using graphics hardware to densely sample the distance field of the rigid object over the arbitrary mesh, we compute minimal proximity and collision response information on the graphics processing unit (GPU) using blending and depth buffering, as well as parallel reduction techniques, thus minimizing the readback bottleneck. Although limited to image-space resolution, our algorithm provides high and steady performance when compared with other similar algorithms. Proximity queries between arbitrary meshes with hundreds of thousands of triangles and detailed distance fields of rigid objects are computed in a few milliseconds at high-sampling resolution, even in situations with large overlap.
High-speed Marching Cubes using HistoPyramids
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Dyken, Christopher; Ziegler, Gernot; Theobalt, Christian; Seidel, Hans-Peter
We present an implementation approach for Marching Cubes (MC) on graphics hardware for OpenGL 2.0 or comparable graphics APIs. It currently outperforms all other known graphics processing units (GPU)-based iso-surface extraction algorithms in direct rendering for sparse or large volumes, even those using the recently introduced geometry shader (GS) capabilites. To achieve this, we outfit the Histogram Pyramid (HP) algorithm, previously only used in GPU data compaction, with the capability for arbitrary data expansion. After reformulation of MC as a data compaction and expansion process, the HP algorithm becomes the core of a highly efficient and interactive MC implementation. For graphics hardware lacking GSs, such as mobile GPUs, the concept of HP data expansion is easily generalized, opening new application domains in mobile visual computing. Further, to serve recent developments, we present how the HP can be implemented in the parallel programming language CUDA (compute unified device architecture), by using a novel 1D chunk/layer construction.
Mapping Highly Detailed Colour Information on Extremely Dense 3D Models: The Case of David s Restoration
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Dellepiane, M.; Callieri, M.; Ponchio, F.; Scopigno, R.
The support of advanced information technology (IT) to preservation, restoration and documentation of Cultural Heritage (CH) is becoming a very important goal for the research community. Michelangelo s David was one of the first applications of 3D scanning technology on a highly popular work of art. The subsequent restoration campaign, started in 2002 and concluded in 2004, was also a milestone for the adoption of modern scientific analysis procedures and IT tools in the framework of a restoration process. One of the focuses in this restoration was also methodological, i.e. to plan and adopt innovative ways to document the restoration process. In this paper, we present the results of an integration of different restoration data (2D and 3D datasets) which has been concluded recently. The recent evolution of HW and SW graphics technologies gave us the possibility to interactively visualize an extremely dense 3D model which incorporates the colour information provided by two professional photographic campaigns, made before and after the restoration. Moreover, we present the results concerning the mapping, in this case on the 2D media, of the reliefs produced by restorers to assess and document the status of the marble surface before the restoration took place. This result could lead to new and fascinating applications of computer graphics for preservation, restoration and documentation of CH.
Peek-in-the-Pic: Flying Through Architectural Scenes From a Single Image*
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Shesh, Amit; Chen, Baoquan
Many casually taken tourist photographs comprise of architectural objects like houses, buildings, etc. Reconstructing such 3D scenes captured in a single photograph is a very challenging problem. We propose a novel approach to reconstruct such architectural scenes with minimal and simple user interaction, with the goal of providing 3D navigational capability to an image rather than acquiring accurate geometric detail. Our system, Peek-in-the-Pic, is based on a sketch-based geometry reconstruction paradigm. Given an image, the user simply traces out objects from it. Our system regards these as perspective line drawings, automatically completes them and reconstructs geometry from them. We make basic assumptions about the structure of traced objects and provide simple gestures for placing additional constraints. We also provide a simple sketching tool to progressively complete parts of the reconstructed buildings that are not visible in the image and cannot be automatically completed. Finally, we fill holes created in the original image when reconstructed buildings are removed from it, by automatic texture synthesis. Users can spend more time using interactive texture synthesis for further refining the image. Thus, instead of looking at flat images, a user can fly through them after some simple processing. Minimal manual work, ease of use and interactivity are the salient features of our approach.
Real-Time Indirect Illumination and Soft Shadows in Dynamic Scenes Using Spherical Lights
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Guerrero, P.; Jeschke, S.; Wimmer, M.
We present a method for rendering approximate soft shadows and diffuse indirect illumination in dynamic scenes. The proposed method approximates the original scene geometry with a set of tightly fitting spheres. In previous work, such spheres have been used to dynamically evaluate the visibility function to render soft shadows. In this paper, each sphere also acts as a low-frequency secondary light source, thereby providing diffuse one-bounce indirect illumination. The method is completely dynamic and proceeds in two passes: In a first pass, the light intensity distribution on each sphere is updated based on sample points on the corresponding object surface and converted into the spherical harmonics basis. In a second pass, this radiance information and the visibility are accumulated to shade final image pixels. The sphere approximation allows us to compute visibility and diffuse reflections of an object at interactive frame rates of over 20 fps for moderately complex scenes.
Table of Contents and Cover
(The Eurographics Association and Blackwell Publishing Ltd, 2008)
Tangible Heritage: Production of Astrolabes on a Laser Engraver
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Zotti, G.
The astrolabe, an analog computing device, used to be the iconic instrument of astronomers during the Middle Ages. It allowed a multitude of operations of practical astronomy which were otherwise cumbersome to perform in an epoch when mathematics had apparently almost been forgotten. Usually made from wood or sheet metal, a few hundred instruments, mostly from brass, survived until today and are valuable museum showpieces. This paper explains a procedural modelling approach for the construction of the classical kinds of astrolabes, which allows a wide variety of applications from plain explanatory illustrations to three-dimensional (3D) models, and even the production of working physical astrolabes usable for public or classroom demonstrations.
Transferring the Rig and Animations from a Character to Different Face Models
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Orvalho, Veronica Costa; Zacur, Ernesto; Susin, Antonio
We introduce a facial deformation system that allows artists to define and customize a facial rig and later apply the same rig to different face models. The method uses a set of landmarks that define specific facial features and deforms the rig anthropometrically. We find the correspondence of the main attributes of a source rig, transfer them to different three-demensional (3D) face models and automatically generate a sophisticated facial rig. The method is general and can be used with any type of rig configuration. We show how the landmarks, combined with other deformation methods, can adapt different influence objects (NURBS surfaces, polygon surfaces, lattice) and skeletons from a source rig to individual face models, allowing high quality geometric or physically-based animations. We describe how it is possible to deform the source facial rig, apply the same deformation parameters to different face models and obtain unique expressions. We enable reusing of existing animation scripts and show how shapes nicely mix one with the other in different face models. We describe how our method can easily be integrated in an animation pipeline. We end with the results of tests done with major film and game companies to show the strength of our proposal.
The Visual Computing of Projector-Camera Systems
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Bimber, Oliver; Iwai, Daisuke; Wetzstein, Gordon; Grundhoefer, Anselm
This article focuses on real-time image correction techniques that enable projector-camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, coloured and textured surfaces. It reviews hardware-accelerated methods like pixel-precise geometric warping, radiometric compensation, multi-focal projection and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super-resolution, high-dynamic range and high-speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.
Untitled
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Leotta, Matthew J.; Vandergon, Austin; Taubin, Gabriel
We present a planarity constraint and a novel three-dimensional (3D) point reconstruction algorithm for a multiview laser range slit scanner. The constraint is based on the fact that all observed points on a projected laser line lie on the same plane of laser light in 3D. The parameters of the plane of laser light linearly parametrize a homography between a pair of images of the laser points. This homography can be recovered from point correspondences derived from epipolar geometry. The use of the planar constraint reduces outliers in the reconstruction and allows for the reconstruction of points seen in only one view. We derive an optimal reconstruction of points subject to the planar constraint and compare the accuracy to the suboptimal approach in prior work. We also construct a catadioptric stereo rig with high quality optical components to remove error due to camera synchronization and non-uniform laser projection. The reconstruction results are compared to prior work that uses inexpensive optics and two cameras.

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