Graphics Research Research Articles

Animations, Games, and Virtual Reality for the Jing-Hang Grand Canal

Digital heritage, an effective method to preserve and present natural and cultural heritage, is engaging many heritage preservation specialists and computer scientists. In particular, computer graphics researchers have become involved, and digital heritage has employed many CG techniques. For example, Daniel Pletinckx and his colleagues employed VR in a real museum at Ename, Belgium, and Zhigeng Pan and his colleagues applied it to construct a virtual Olympics museum. Soo-Chang Pei and his colleagues focused on restoring ancient Chinese paintings. Here, we describe how we've applied animations, computer games, and VR to China's famous Jing-Hang Grand Canal.

A software tool for generating graphics by means of P systems

The hand-made graphical representation of the configuration of a P system becomes a hard task when the number of membranes and objects increases. In this paper we present a new software tool, called JPLANT, for computing and representing the evolution of a P system model with membrane creation. We also present some experiments performed with JPLANT and point out new lines for the research in computer graphics with membrane systems.

Modelling the Appearance and Behaviour of Urban Spaces

Abstract Urban spaces consist of a complex collection of buildings, parcels, blocks and neighbourhoods interconnected by streets. Accurately modelling both the appearance and the behaviour of dense urban spaces is a significant challenge. The recent surge in urban data and its availability via the Internet has fomented a significant amount of research in computer graphics and in a number of applications in urban planning, emergency management and visualization. In this paper, we seek to provide an overview of methods spanning computer graphics and related fields involved in this goal. Our paper reports the most prominent methods in urban modelling and rendering, urban visualization and urban simulation models. A reader will be well versed in the key problems and current solution methods.

Hair meshes

Despite the visual importance of hair and the attention paid to hair modeling in the graphics research, modeling realistic hair still remains a very challenging task that can be performed by very few artists. In this paper we present hair meshes , a new method for modeling hair that aims to bring hair modeling as close as possible to modeling polygonal surfaces. This new approach provides artists with direct control of the overall shape of the hair, giving them the ability to model the exact hair shape they desire. We use the hair mesh structure for modeling the hair volume with topological constraints that allow us to automatically and uniquely trace the path of individual hair strands through this volume. We also define a set of topological operations for creating hair meshes that maintain these constraints. Furthermore, we provide a method for hiding the volumetric structure of the hair mesh from the end user, thus allowing artists to concentrate on manipulating the outer surface of the hair as a polygonal surface. We explain and show examples of how hair meshes can be used to generate individual hair strands for a wide variety of realistic hair styles.

Cooperative virtual worlds—a viable eCollaboration pathway or merely a gaming trend?

With research and technology advances in networking and computer graphics, cooperative virtual environments (CVEs), 3D virtual worlds, which can be used by multiple persons that are represented in the virtual world through avatars, are becoming increasingly popular. In this short position paper we discuss whether or not CVEs are a lasting phenomenon with impact on eCollabopration practice and CSCW research or just an isolated phenomenon in the gaming community. In doing so, this paper outlines four application areas that CVEs are successful in (games, leisure, education, business) and presents opportunities, risks and research challenges that are associated with using CVEs as eCollaboration tools.

Issues in image-guided therapy [A Look at . . .

M edical robotics, computer- assisted surgery (CAS), image-guided therapy (IGT), and the like emerged more than 20 years ago, and many advances have been made since. Conferences and workshops have been organized; scientific contributions, position papers, and patents have been published; new academic societies have been launched; and companies were created all over the world to propose methods, devices, and systems in the area. Researchers in robotics, computer vision and graphics, electronics, mechanics, biomedical engineers, physicians, and surgeons have been involved, thus demonstrating the enthusiasm for this emerging field. Their commitments emphasize the transdisciplinary nature of the efforts to be made. However, the effective dissemination of CAS-IGT systems in medical disciplines remains limited. There are several reasons that may explain this situation, among which the effective demonstration of patient benefits and cost savings, the reluctance of surgeons or therapists to use them, and, of course, the technological breakthroughs are still expected. This series of articles attempts to point out some of them and will also show that many opportunities in computer-assisted interventions are open in the near future.

PatchMatch

This paper presents interactive image editing tools using a new randomized algorithm for quickly finding approximate nearest-neighbor matches between image patches. Previous research in graphics and vision has leveraged such nearest-neighbor searches to provide a variety of high-level digital image editing tools. However, the cost of computing a field of such matches for an entire image has eluded previous efforts to provide interactive performance. Our algorithm offers substantial performance improvements over the previous state of the art (20-100x), enabling its use in interactive editing tools. The key insights driving the algorithm are that some good patch matches can be found via random sampling, and that natural coherence in the imagery allows us to propagate such matches quickly to surrounding areas. We offer theoretical analysis of the convergence properties of the algorithm, as well as empirical and practical evidence for its high quality and performance. This one simple algorithm forms the basis for a variety of tools -- image retargeting, completion and reshuffling -- that can be used together in the context of a high-level image editing application. Finally, we propose additional intuitive constraints on the synthesis process that offer the user a level of control unavailable in previous methods.

Guest Editors' Introduction: Virtual Populace

Only in the ruins of post-apocalyptic cities would the absence of living entities be appropriate, whereas real environments are filled with characters, whether they're alone, in groups, or congregating in large crowds. Therefore, the simulation of populated environments is one of the most active and expanding areas of computer graphics research today. There are two main reasons for this. First, owing to the problem space's complexity, many research challenges remain to be solved. Second, a huge demand exists in many application domains (for example, games, movies, and architectural design) for convincing and scalable populace. Virtual populace is an extension of crowd-modeling research in computer graphics that encompasses activity selection, graphics portrayal, implementation architectures, and perceptual features. This special issue features articles addressing these and related issues.

3D virtual mosaics: Opus Palladium and mixed styles

One of the oldest art forms, mosaics are built by careful selection and placement of small pieces called tiles. Although 2D mosaics have attracted attention in computer graphics research, 3D virtual mosaic sculptures are less common. In this work, we present a method to simulate mosaic sculptures using tiles with irregular shapes, a method known by mosaicists as Opus Palladium, or simply “crazy paving,” due to the inherent freedom of mixing the tiles. In order to add expressiveness and emphasize some features, artists distribute the tiles following a high-level design over the shape. We use Voronoi polygons to represent the tiles computed from a distribution of points on the surface of the 3D object. We also address the simulation of mixed mosaics, where both irregular and squared-shape tiles are used on the same object. Previous works on such surface mosaics have used only square-shaped tiles, with fixed or variable size. Special mosaic-like effects are obtained with the help from texture maps, which control the high-level design of the tile distribution.

“Smart Approaches” to Lighting DesignIntelligente Komposition von Lichtquellen in Computergraphiken

Abstract The declarative design of graphics lies at the core of the Smart Graphics research agenda. For 3D graphics the number of lights included, and the properties of these lights, has an enormous impact on what a viewer can judge about the content (the objects), properties (the geometric characteristics and spatial relations of the objects) and other aesthetic qualities of a scene. The traditional approach to lighting design for image synthesis is based on manual design methods, whereby users interactively specify values of lighting parameters, render the scene, and modify the lighting parameters until the desired visual properties of the scene are achieved. Non-expert users encounter a number of difficulties in selecting the appropriate lighting parameters, as the process requires both a subtle technical and aesthetic understanding of lighting in computer graphics. We review range of “smart” lighting design and steady slow convergence on ideal lighting approaches which optimise the lighting configuration for a scene with respect to a set of absolute perceptual metrics. More recently perceptual approaches have been combined with aspects of exemplar driven approaches to yield “lighting-by-example” techniques that can replicate the lighting of existing static 2D images and 3D scenes.

Animating Virtual Speakers or Singers from Audio: Lip-Synching Facial Animation

The aim of this special issue is to provide a detailed description of state-of-the-art systems for animating faces during speech, and identify new techniques that have recently emerged from both the audiovisual speech and computer graphics research communities. This special issue is a followup to the first LIPS Visual Speech Synthesis Challenge held as a special session at INTERSPEECH 2008 in Brisbane, Australia. As a motivation for the present special issue, we will report on the LIPS Challenge with respect to the synthesis techniques, andmore importantly the methods and results of the subjective evaluation.

A Hierarchical Hashing Scheme for Nearest Neighbor Search and Broad-Phase Collision Detection

Increasing computational power allows computer graphics researchers to model spectacular phenomena such as fluids and their interactions with deformable objects and structures. Particle-based (or Lagrangian) fluid and solid simulations are commonly managed separately and mixed together for the collision detection phase. We present a unified dynamic acceleration model to be used for particle neighborhood queries and broad-phase collision detection, based on a hierarchical hash table data structure. Our method is able to significantly reduce computations in large, empty areas, and thus gives better results than existing acceleration techniques, such as multilevel hashing schemes or KD-trees, in most situations.

Reconstructing head models from photographs for individualized 3D‐audio processing

AbstractVisual fidelity and interactivity are the main goals in Computer Graphics research, but recently also audio is assuming an important role. Binaural rendering can provide extremely pleasing and realistic three‐dimensional sound, but to achieve best results it's necessary either to measure or to estimate individual Head Related Transfer Function (HRTF). This function is strictly related to the peculiar features of ears and face of the listener. Recent sound scattering simulation techniques can calculate HRTF starting from an accurate 3D model of a human head. Hence, the use of binaural rendering on large scale (i.e. video games, entertainment) could depend on the possibility to produce a sufficiently accurate 3D model of a human head, starting from the smallest possible input. In this paper we present a completely automatic system, which produces a 3D model of a head starting from simple input data (five photos and some key‐points indicated by user). The geometry is generated by extracting information from images and accordingly deforming a 3D dummy to reproduce user head features. The system proves to be fast, automatic, robust and reliable: geometric validation and preliminary assessments show that it can be accurate enough for HRTF calculation.

A Basis Illumination Approach to BRDF Measurement

Realistic descriptions of surface reflectance have long been a topic of interest in both computer vision and computer graphics research. In this paper, we describe a novel high speed approach for the acquisition of bidirectional reflectance distribution functions (BRDFs). We develop a new theory for directly measuring BRDFs in a basis representation by projecting incident light as a sequence of basis functions from a spherical zone of directions. We derive an orthonormal basis over spherical zones that is ideally suited for this task. BRDF values outside the zonal directions are extrapolated by re-projecting the zonal measurements into a spherical harmonics basis, or by fitting analytical reflection models to the data. For specular materials, we experiment with alternative basis acquisition approaches such as compressive sensing with a random subset of the higher order orthonormal zonal basis functions, as well as measuring the response to basis defined by an analytical model as a way of optically fitting the BRDF to such a representation. We verify this approach with a compact optical setup that requires no moving parts and only a small number of image measurements. Using this approach, a BRDF can be measured in just a few minutes.

The State of the Art in Mobile Graphics Research

High-quality computer graphics let mobile-device users access more compelling content. Still, the devices' limitations and requirements differ substantially from those of a PC. This survey of mobile graphics research describes current solutions in terms of specialized hardware (including 3D displays), rendering and transmission, visualization, and user interfaces.

3D mosaics with variable-sized tiles

Three dimensional mosaics, or surface mosaics, are a beautiful art form where a sculpture is made from putting together tiles on a given shape. Although 2D mosaics have attracted a lot of attention in graphics research, the same is not true for 3D mosaics. We present in this paper a technique to simulate 3D mosaics where the size of the individual pieces vary according to the local geometry. Previous work on this topic have addressed the problem of mosaics with tiles of the same size. The user specifies the number of tiles and our system covers a given 3D shape with square-shaped tiles with size adjusted according to the local curvature of the surface. The user can also controls the number of tiles, orientation on the surface, and relative size of tiles.

Visualizing and Analyzing the Mona Lisa

Size and scale issues present a complexity problem in visualizing detailed 3D models built from sensor data. A model of Leonardo da Vinci's Mona Lisa, with its thin pictorial layer, illustrates the need for intuitive real-time processing tools that are seamlessly integrated with a multiresolution visualization environment.

실감형 콘텐츠 제작을 위한 3D 자연환경 저작 소프트웨어 개발

3D 콘텐츠의 등장인물과 실내 환경 구현에 집중하던 개발자들은 하드웨어 성능의 빠른 향상과 야외환경을 배경으로 제작되는 콘텐츠의 수요가 증가됨에 따라 사실적인 3D 야외환경을 표현하기 위한 자연현상 표현 기술 개발에 관심을 두고 있다. 특히, 야외를 배경으로 제작되는 e-sports 콘텐츠와 시뮬레이션 콘텐츠는 더욱 사실적인 자연환경 표현이 중요하다. 본 논문에서는 실외를 배경으로 하는 e-sports 콘텐츠 및 3D 시뮬레이션 콘텐츠에 적용할 수 있는 사실적인 3D 자연환경을 보다 쉽고 편리하게 제작하기 위한 소프트웨어 "EMtool(Environment Making Tool)"을 제안한다. EMtool은 자연현상들의 유대관계 및 상호작용을 사실적으로 표현하기 위한 기술에 중점을 두고 개발되었으며, 3D가상공간 내에서 자연환경을 표현하기 위한 기술들과 자연물을 표현하기 위한 기술들을 포함한다. 제안된 방법은 쉽고 빠르게 3D 야외 환경 구성이 가능함에 따라 사실적인 자연환경을 배경으로 제작되는 게임이나 가상 시뮬레이션 등 실시간 3D 콘텐츠에 활용이 가능할 것이다. 또한 사실적인 3D 자연환경 제작 기술을 제공함으로서 콘텐츠의 품질 향상은 물론 콘텐츠 맞춤형 3D 자연환경을 실시간에 제작할 수 있음으로 생산성을 증대시킬 수 있을 것이다. Nowadays, many graphic researchers are interested in 3D outdoor environment. They want to express more realistic natural background with natural phenomenon because computer hardware has become more powerful and increased a demand for a background of 3D natural environment in a content. Especially, e-sports contents and simulation contents with outdoor environment need more natural environment for a background than indoor contents. It is very important technology for a quality of 3D outdoor contents. We propose a software EMtool(Environment Making Tool) for authoring of natural environment for realistic contents. EMtool has been developed to depict relationship and interaction between natural phenomena and include methods for creating natural environment and natural objects. The proposed results are applied to real-time 3D contents such as 3D golf games and simulations for natural objects.

Increasing student retention in computer science through research programs for undergraduates

To address the alarming decrease in students in Rhode Island computer science programs and the under-representation of women and minorities, we have devised a program to introduce students to research in computer graphics, art and new media. This program integrates good mentoring practice and pedagogy, including problem-based learning. Special attention is paid to creating a cohort of students who come together every week to learn about the research process, and ethical and societal issues related to it. Each student takes a small project from the proposal stage, through design and implementation, to publication and presentation. We report on the first two years of the program.

Vascular Modeling from Volumetric Diagnostic Data: A Review

Reconstruction of vascular trees from digital diagnostic images is a challenging task in the development of tools for simulation and procedural planning for clinical use. Improvements in quality and resolution of acquisition modalities are constantly increasing the fields of application of computer assisted techniques for vascular modeling and a lot of Computer Vision and Computer Graphics research groups are currently active in the field, developing methodologies, algorithms and software prototypes able to recover models of branches of human vascular system from different kinds of input images. Reconstruction methods can be extremely different according to image type, accuracy requirements and level of automation. Some technologies have been validated and are available on medical workstation, others have still to be validated in clinical environments. It is difficult, therefore, to give a complete overview of the different approach used and results obtained, this paper just presents a short review including some examples of the principal reconstruction approaches proposed for vascular reconstruction, showing also the contribution given to the field by the Medical Application Area of CRS4, where methods to recover vascular models have been implemented and used for blood flow analysis, quantitative diagnosis and surgical planning tools based on Virtual Reality. Keywords: Vessel, CT, MRI, Segmentation, 3D