Volume 29 (2010)

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https://diglib.eg.org/handle/10.2312/151

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Seamless Montage for Texturing Models
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gal, Ran; Wexler, Yonatan; Ofek, Eyal; Hoppe, Hugues; Cohen-Or, Daniel
We present an automatic method to recover high-resolution texture over an object by mapping detailed photographs onto its surface. Such high-resolution detail often reveals inaccuracies in geometry and registration, as well as lighting variations and surface reflections. Simple image projection results in visible seams on the surface. We minimize such seams using a global optimization that assigns compatible texture to adjacent triangles. The key idea is to search not only combinatorially over the source images, but also over a set of local image transformations that compensate for geometric misalignment. This broad search space is traversed using a discrete labeling algorithm, aided by a coarse-to-fine strategy. Our approach significantly improves resilience to acquisition errors, thereby allowing simple and easy creation of textured models for use in computer graphics.
Multi-Perspective Modelling, Rendering and Imaging
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Yu, J.; McMillan, L.; Sturm, P.
A perspective image represents the spatial relationships of objects in a scene as they appear from a single viewpoint. In contrast, a multi-perspective image combines what is seen from several viewpoints into a single image. Despite their incongruity of view, effective multi-perspective images are able to preserve spatial coherence and can depict, within a single context, details of a scene that are simultaneously inaccessible from a single view, yet easily interpretable by a viewer. In computer vision, multi-perspective images have been used for analysing structure revealed via motion and generating panoramic images with a wide field-of-view using mirrors.In this STAR, we provide a practical guide on topics in multi-perspective modelling and rendering methods and multi-perspective imaging systems. We start with a brief review of multi-perspective image techniques frequently employed by artists such as the visual paradoxes of Escher, the Cubism of Picasso and Braque and multi-perspective panoramas in cel animations. We then characterize existing multi-perspective camera models, with an emphasis on their underlying geometry and image properties. We demonstrate how to use these camera models for creating specific multi-perspective rendering effects. Furthermore, we show that many of these cameras satisfy the multi-perspective stereo constraints and we demonstrate several multi-perspective imaging systems for extracting 3D geometry for computer vision.The participants learn about topics in multi-perspective modelling and rendering for generating compelling pictures for computer graphics and in multi-perspective imaging for extracting 3D geometry for computer vision. We hope to provide enough fundamentals to satisfy the technical specialist without intimidating curious digital artists interested in multi-perspective images.The intended audience includes digital artists, photographers and computer graphics and computer vision researchers using or building multi-perspective cameras. They will learn about multi-perspective modelling and rendering, along with many real world multi-perspective imaging systems.
Video Visualization for Snooker Skill Training
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Höferlin, Markus; Grundy, Edward; Borgo, Rita; Weiskopf, Daniel; Chen, Min; Griffiths, Iwan W.; Griffiths, W.; G. Melancon, T. Munzner, and D. Weiskopf
We present a feasibility study on using video visualization to aid snooker skill training. By involving the coaches and players in the loop of intelligent reasoning, our approach addresses the difficulties of automated semantic reasoning, while benefiting from mature video processing techniques. This work was conducted in conjunction with a snooker club and a sports scientist. In particular, we utilized the principal design of the VideoPerpetuoGram (VPG) to convey spatiotemporal information to the viewers through static visualization, removing the burden of repeated video viewing. We extended the VPG design to accommodate the need for depicting multiple video streams and respective temporal attribute fields, including silhouette extrusion, spatial attributes, and non-spatial attributes. Our results and evaluation have shown that video visualization can provide snooker coaching with visually quantifiable and comparable summary records, and is thus a cost-effective means for assessing skill levels and monitoring progress objectively and consistently.
Evaluation of an Augmented Reality Supported Picking System Under Practical Conditions
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Reif, R.; Guenthner, W. A.; Schwerdtfeger, B.; Klinker, G.
Order picking is one of the most important process steps in logistics. Because of their flexibility, human beings cannot be replaced by machines. But if workers, in order, picking systems are equipped with a head-mounted display, Augmented Reality can improve the information visualization. In this paper, the development of such a system-called Pick-by-Vision-is presented. The system is evaluated in a user study performed in a real storage environment. Important logistics figures as well as the subjective strain were measured. The results show that a Pick-by-Vision system can considerably improve industrial order picking processes.
Fast Generation of Pointerless Octree Duals
(2010) Thomas Lewiner; Vinicius Mello; Adelailson Peixoto; Sinesio Pesco; Helio Lopes
Geometry processing applications frequently rely on octree structures, since they provide simple and efficient hierarchies for discrete data. However, octrees do not guarantee direct continuous interpolation of this data inside its nodes. This motivates the use of the octree's dual structure, which is one of the simplest continuous hierarchical structures. With the emergence of pointerless representations, with their ability to reduce memory footprint and adapt to parallel architectures, the generation of duals of pointerless octrees becomes a natural challenge. This work proposes strategies for dual generation of static or dynamic pointerless octrees. Experimentally, those methods enjoy the memory reduction of pointerless representations and speed up the execution by several factors compared to the usual recursive generation.
A Dynamic Noise Primitive for Coherent Stylization
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Benard, P.; Lagae, A.; Vangorp, P.; Lefebvre, S.; Drettakis, G.; Thollot, J.
We present a new solution for temporal coherence in non-photorealistic rendering (NPR) of animations. Given the conflicting goals of preserving the 2D aspect of the style and the 3D scene motion, any such solution is a tradeoff. We observe that primitive-based methods in NPR can be seen as texture-based methods when using large numbers of primitives, leading to our key insight, namely that this process is similar to sparse convolution noise in procedural texturing. Consequently, we present a new primitive for NPR based on Gabor noise, that preserves the 2D aspect of noise, conveys the 3D motion of the scene, and is temporally continuous. We can thus use standard techniques from procedural texturing to create various styles, which we show for interactive NPR applications. We also present a user study to evaluate this and existing solutions, and to provide more insight in the trade-off implied by temporal coherence. The results of the study indicate that maintaining coherent motion is important, but also that our new solution provides a good compromise between the 2D aspect of the style and 3D motion.
Embedded Implicit Stand-Ins for Animated Meshes: A Case of Hybrid Modelling
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Kravtsov, D.; Fryazinov, O.; Adzhiev, V.; Pasko, A.; Comninos, P.
In this paper, we address shape modelling problems, encountered in computer animation and computer games development that are difficult to solve just using polygonal meshes. Our approach is based on a hybrid-modelling concept that combines polygonal meshes with implicit surfaces. A hybrid model consists of an animated polygonal mesh and an approximation of this mesh by a convolution surface stand-in that is embedded within it or is attached to it. The motions of both objects are synchronised using a rigging skeleton. We model the interaction between an animated mesh object and a viscoelastic substance, which is normally represented in an implicit form. Our approach is aimed at achieving verisimilitude rather than physically based simulation. The adhesive behaviour of the viscous object is modelled using geometric blending operations on the corresponding implicit surfaces. Another application of this approach is the creation of metamorphosing implicit surface parts that are attached to an animated mesh. A prototype implementation of the proposed approach and several examples of modelling and animation with near real-time preview times are presented.
Patch-based Texture Interpolation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Ruiters, Roland; Schnabel, Ruwen; Klein, Reinhard
In this paper, we present a novel exemplar-based technique for the interpolation between two textures that combines patch-based and statistical approaches. Motivated by the notion of texture as a largely local phenomenon, we warp and blend small image neighborhoods prior to patch-based texture synthesis. In addition, interpolating and enforcing characteristic image statistics faithfully handles high frequency detail. We are able to create both intermediate textures as well as continuous transitions. In contrast to previous techniques computing a global morphing transformation on the entire input exemplar images, our localized and patch-based approach allows us to successfully interpolate between textures with considerable differences in feature topology for which no smooth global warping field exists.
A Data-driven Segmentation for the Shoulder Complex
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Hong, Q Youn; Park, Sang Il; Hodgins, Jessica K.
The human shoulder complex is perhaps the most complicated joint in the human body being comprised of a set of three bones, muscles, tendons, and ligaments. Despite this anatomical complexity, computer graphics models for motion capture most often represent this joint as a simple ball and socket. In this paper, we present a method to determine a shoulder skeletal model that, when combined with standard skinning algorithms, generates a more visually pleasing animation that is a closer approximation to the actual skin deformations of the human body. We use a data-driven approach and collect ground truth skin deformation data with an optical motion capture system with a large number of markers (200 markers on the shoulder complex alone). We cluster these markers during movement sequences and discover that adding one extra joint around the shoulder improves the resulting animation qualitatively and quantitatively yielding a marker set of approximately 70 markers for the complete skeleton. We demonstrate the effectiveness of our skeletal model by comparing it with ground truth data as well as with recorded video. We show its practicality by integrating it with the conventional rendering/animation pipeline.
Streaming-Enabled Parallel Dataflow Architecture for Multicore Systems
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Vo, Huy T.; Osmari, Daniel K.; Summa, Brian; Comba, João L. D.; Pascucci, Valerio; Silva, Cláudio T.; G. Melancon, T. Munzner, and D. Weiskopf
We propose a new framework design for exploiting multi-core architectures in the context of visualization dataflow systems. Recent hardware advancements have greatly increased the levels of parallelism available with all indications showing this trend will continue in the future. Existing visualization dataflow systems have attempted to take advantage of these new resources, though they still have a number of limitations when deployed on shared memory multi-core architectures. Ideally, visualization systems should be built on top of a parallel dataflow scheme that can optimally utilize CPUs and assign resources adaptively to pipeline elements. We propose the design of a flexible dataflow architecture aimed at addressing many of the shortcomings of existing systems including a unified execution model for both demand-driven and event-driven models; a resource scheduler that can automatically make decisions on how to allocate computing resources; and support for more general streaming data structures which include unstructured elements. We have implemented our system on top of VTK with backward compatibility. In this paper, we provide evidence of performance improvements on a number of applications.
Time-of-Flight Cameras in Computer Graphics
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Kolb, A.; Barth, E.; Koch, R.; Larsen, R.
A growing number of applications depend on accurate and fast 3D scene analysis. Examples are model and lightfield acquisition, collision prevention, mixed reality and gesture recognition. The estimation of a range map by image analysis or laser scan techniques is still a time-consuming and expensive part of such systems.A lower-priced, fast and robust alternative for distance measurements are time-of-flight (ToF) cameras. Recently, significant advances have been made in producing low-cost and compact ToF devices, which have the potential to revolutionize many fields of research, including computer graphics, computer vision and human machine interaction (HMI).These technologies are starting to have an impact on research and commercial applications. The upcoming generation of ToF sensors, however, will be even more powerful and will have the potential to become ubiquitous real-time geometry devices for gaming, web-conferencing, and numerous other applications. This paper gives an account of recent developments in ToF technology and discusses the current state of the integration of this technology into various graphics-related applications.
Global Illumination Compensation for Spatially Augmented Reality
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sheng, Yu; Yapo, Theodore C.; Cutler, Barbara
When projectors are used to display images on complex, non-planar surface geometry, indirect illumination between the surfaces will disrupt the final appearance of this imagery, generally increasing brightness, decreasing contrast, and washing out colors. In this paper we predict through global illumination simulation this unintentional indirect component and solve for the optimal compensated projection imagery that will minimize the difference between the desired imagery and the actual total illumination in the resulting physical scene. Our method makes use of quadratic programming to minimize this error within the constraints of the physical system, namely, that negative light is physically impossible. We demonstrate our compensation optimization in both computer simulation and physical validation within a table-top spatially augmented reality system. We present an application of these results for visualization of interior architectural illumination. To facilitate interactive modifications to the scene geometry and desired appearance, our system is accelerated with a CUDA implementation of the QP optimization method.
B-Mesh: A Modeling System for Base Meshes of 3D Articulated Shapes
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Ji, Zhongping; Liu, Ligang; Wang, Yigang
This paper presents a novel modeling system, called B-Mesh, for generating base meshes of 3D articulated shapes. The user only needs to draw a one-dimensional skeleton and to specify key balls at the skeletal nodes. The system then automatically generates a quad dominant initial mesh. Further subdivision and evolution are performed to refine the initial mesh and generate a quad mesh which has good edge flow along the skeleton directions. The user can also modify and manipulate the shape by editing the skeleton and the key balls and can easily compose new shapes by cutting and pasting existing models in our system. The mesh models generated in our system greatly benefit the sculpting operators for sculpting modeling and skeleton-based animation.
An Evaluation of Glyph Perception for Real Symmetric Traceless Tensor Properties
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Jankun-Kelly, T. J.; Lanka, Yagneshwara; II, J. Edward Swan; G. Melancon, T. Munzner, and D. Weiskopf
A perceptual study of four tensor glyphs for symmetric, real, traceless tensors was performed. Each glyph encodes three properties of the system: Orientation, uniaxiality (alignment along the direction of orientation), and biaxiality (alignment along a vector orthogonal to the orientation). Thirty users over two studies were asked to identify these three properties for each glyph type under a variety of permutations in order to evaluate the effectiveness of visually communicating the properties; response time was also measured. We discuss the significant differences found between the methods as guidance to the use of these glyphs for traceless tensor visualization.
Real-Time Concurrent Linked List Construction on the GPU
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Yang, Jason C.; Hensley, Justin; Gruen, Holger; Thibieroz, Nicolas
We introduce a method to dynamically construct highly concurrent linked lists on modern graphics processors. Once constructed, these data structures can be used to implement a host of algorithms useful in creating complex rendering effects in real time. We present a straightforward way to create these linked lists using generic atomic operations available in APIs such as OpenGL 4.0 and DirectX 11. We also describe several possible applications of our algorithm. One example uses per-pixel linked lists for order-independent transparency; as a consequence, we are able to directly implement fully programmable blending, which frees developers from the restrictions imposed by current graphics APIs. The second uses linked lists to implement real-time indirect shadows.
Understanding Interactive Legends: a Comparative Evaluation with Standard Widgets
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Riche, Nathalie Henry; Lee, Bongshin; Plaisant, Catherine; G. Melancon, T. Munzner, and D. Weiskopf
Interactive information visualization systems rely on widgets to allow users to interact with the data and modify the representation. We define interactive legends as a class of controls combining the visual representation of static legends and interaction mechanisms of widgets. As interactive legends start to appear in popular websites, we categorize their designs for common data types and evaluate their effectiveness compare to standard widgets. Results suggest that 1) interactive legends can lead to faster perception of the mapping between data values and visual encodings and 2) interaction time is affected differently depending on the data type. Additionally, our study indicates superiority both in terms of perception and interaction of ordinal controls over numerical ones. Numerical techniques are mostly used in today s systems. By providing solutions to allowing users to modify ranges interactively, we believe that interactive legends make it possible to increase the use of ordinal techniques for visual exploration.
Arbitrary Importance Functions for Metropolis Light Transport
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Hoberock, Jared; Hart, John C.
We present a generalization of the scalar importance function employed by Metropolis Light Transport (MLT) and related Markov chain rendering algorithms. Although MLT is known for its user-designable mutation rules, we demonstrate that its scalar contribution function is similarly programmable in an unbiased manner. Normally, MLT samples light paths with a tendency proportional to their brightness. For a range of scenes, we demonstrate that this importance function is undesirable and leads to poor sampling behaviour. Instead, we argue that simple user-designable importance functions can concentrate work in transport effects of interest and increase estimator efficiency. Unlike mutation rules, these functions are not encumbered with the calculation of transitional probabilities. We introduce alternative importance functions, which encourage the Markov chain to aggressively pursue sampling goals of interest to the user. In addition, we prove that these importance functions may adapt over the course of a render in an unbiased fashion. To that end, we introduce multi-stage MLT, a general rendering setting for creating such adaptive functions. This allows us to create a noise-sensitive MLT renderer whose importance function explicitly targets noise. Finally, we demonstrate that our techniques are compatible with existing Markov chain rendering algorithms and significantly improve their visual efficiency.
Designing a Highly Immersive Interactive Environment: The Virtual Mine
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Soares, L. P.; Pires, F.; Varela, R.; Bastos, R.; Carvalho, N.; Gaspar, F.; Dias, M. S.
To achieve a full-scale simulation of a pyrite mine, a highly immersive environment becomes necessary and this research has led to a complex system enabling users to walk through a virtual mine in real time, presenting all the behaviours present in such environment. Some of the problems encountered are the tunnels behaviours, including highly contrasted images due to the presence of the head light, narrow paths, elevators, sound reverberation and tunnels texture shades. The use of immersive virtual reality enables the generation of high-quality simulations, because it is possible to control several feedback mechanisms such as the degree of luminance of produced imagery and spatial sound. In this research, a projection infrastructure and tracking system were specified and developed, aiming at producing the best results for this kind of simulation. To achieve our purposes, distributed algorithms were developed to run in a cluster solution that drives a four-sided CAVE-like environment. The complete production pipeline is presented, ranging from the developed authoring techniques, enabling fast production of new content for the simulation, to the tracking techniques produced for the improvement of the interaction.
A Survey of Procedural Noise Functions
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lagae, A.; Lefebvre, S.; Cook, R.; DeRose, T.; Drettakis, G.; Ebert, D.S.; Lewis, J.P.; Perlin, K.; Zwicker, M.
Procedural noise functions are widely used in computer graphics, from off-line rendering in movie production to interactive video games. The ability to add complex and intricate details at low memory and authoring cost is one of its main attractions. This survey is motivated by the inherent importance of noise in graphics, the widespread use of noise in industry and the fact that many recent research developments justify the need for an up-to-date survey. Our goal is to provide both a valuable entry point into the field of procedural noise functions, as well as a comprehensive view of the field to the informed reader. In this report, we cover procedural noise functions in all their aspects. We outline recent advances in research on this topic, discussing and comparing recent and well-established methods. We first formally define procedural noise functions based on stochastic processes and then classify and review existing procedural noise functions. We discuss how procedural noise functions are used for modelling and how they are applied to surfaces. We then introduce analysis tools and apply them to evaluate and compare the major approaches to noise generation. We finally identify several directions for future work.
DTI in Context: Illustrating Brain Fiber Tracts In Situ
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Svetachov, Pjotr; Everts, Maarten H.; Isenberg, Tobias; G. Melancon, T. Munzner, and D. Weiskopf
We present an interactive illustrative visualization method inspired by traditional pen-and-ink illustration styles. Specifically, we explore how to provide context around DTI fiber tracts in the form of surfaces of the brain, the skull, or other objects such as tumors. These contextual surfaces are derived from either segmentation data or generated using interactive iso-surface extraction and are rendered with a flexible, slice-based hatching technique, controlled with ambient occlusion. This technique allows us to produce a consistent and frame-coherent appearance with precise control over the lines. In addition, we provide context through cutting planes onto which we render gray matter with stippling. Together, our methods not only facilitate the interactive exploration and illustration of brain fibers within their anatomical context but also allow us to produce high-quality images for print reproduction. We provide evidence for the success of our approach with an informal evaluation with domain experts.

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