Die »Selected Readings in Computer Graphics 2013« bestehen aus 40 ausgewählten Artikeln von insgesamt 192 wissenschaftlichen Veröffentlichungen. 

Die Beiträge kommen aus dem Fraunhofer-Institut für Graphische Datenverarbeitung IGD mit Standorten in Darmstadt wie auch in Rostock, Singapur und Graz, den Partner-Instituten an den jeweiligen Universitäten, der Fachgruppe Graphisch-Interaktive Systeme der Technischen Universität Darmstadt, der Computergraphics and Communication Gruppe am Institut für Informatik der Universität Rostock, der Nanyang Technological University (NTU), Singapur, und dem Visual Computing Excellenz-Cluster der Technischen Universität Graz. Sie alle arbeiten eng in Projekten sowie Forschung und Entwicklung im Gebiet der Computer Graphik zusammen.

Alle Artikel erschienen vorher in verschiedenen wissenschaftlichen Büchern, Zeitschriften, Konferenzbänden und Workshops. Die Veröffentlichungen mussten einen gründlichen Begutachtungsprozess durch international führende Experten und etabilierte technische Vereinigungen durchlaufen. Deshalb geben die Selected Readings einen recht guten und detaillierten Überblick über die wissenschaftlichen Entwicklungen in der Computer Graphik im Jahr 2013. Sie werden von Professor Dieter W. Fellner, dem Leiter des Fraunhofer-Instituts für Graphische Datenverarbeitung IGD in Darmstadt zusammengestellt. Er ist zugleich Professor am Fachbereich Informatik der Technischen Universität Darmstadt und Professor an der Fakultät für Informatik der Technischen Universität Graz.

Die Selected Readings in Computer Graphics 2013 befassen sich mit Aspekten und Trends der Forschung und Entwicklung in Computer Graphik auf den Gebieten

  • Digitale Gesellschaft
  • Virtuelles Engineering
  • Visuelle Entscheidungshilfe

Liste der Publikationen

Aderhold, Andreas; Jung, Yvonne; Wilkosinska, Katarzyna; Fellner, Dieter W.

Distributed 3D Model Optimization for the Web with the Common Implementation Framework for Online Virtual Museums

2013

2013 Digital Heritage International Congress. Volume 2 : DigitalHeritage. New York: The Institute of Electrical and Electronics Engineers (IEEE), 2013, pp. 719-726

Digital Heritage International Congress (DigitalHeritage) <2013, Marseille, France>

Internet services are becoming more ubiquitous and 3D graphics is increasingly gaining a strong foothold in the Web technology domain. Recently, with WebGL, real-time 3D graphics in the Browser became a reality and most major Browsers support WebGL natively today. This makes it possible to create applications like 3D catalogs of artifacts, or to interactively explore Cultural Heritage objects in a Virtual Museum on mobile devices. Frameworks like the open-source system X3DOM provide declarative access to low-level GPU routines along with seamless integration of 3D graphics into HTML5 applications through standardized Web technologies.

Most 3D models also need to be optimized to address concerns like limited network bandwidth or reduced GPU power on mobile devices. Therefore, recently an online platform for the development of Virtual Museums with particular attention to presentation and visualization of Cultural Heritage assets in online virtual museums was proposed. This common implementation Framework (CIF) allows the user to upload large 3D models, which are subsequently converted and optimized for web display and embedded in an HTML5 application that can range from simple interactive display of the model to an entire virtual environment like a virtual walk-through. Generating these various types of applications is done via a templating mechanism, which will be further elaborated within this paper. Moreover, to efficiently convert many large models into an optimized form, a substantial amount of computing power is required, which a single system cannot yet provide in a timely fashion. Therefore, we also describe
how the CIF can be used to utilize a dynamically allocated cloud-based or physical cluster of commodity hardware to distribute the workload of model optimization for the Web.

Aehnelt, Mario; Bader, Sebastian; Ruscher, Gernot; Krüger, Frank; Urban, Bodo; Kirste, Thomas

Situation Aware Interaction with Multi-Modal Business Applications in Smart Environments

2013

Yamamoto, Sakae (Ed.): Human Interface and the Management of Information: Part III : Information and Interaction for Learning, Culture, Collaboration and Business. 15th International Conference, HCI International 2013. Berlin, Heidelberg, New York: Springer, 2013. (Lecture Notes in Computer Science (LNCS) 8018), pp. 413-422

International Conference on Human-Computer Interaction (HCII) <15, 2013, Las Vegas, NV, USA>

A consistent user experience in combination with proactive assistance may improve the user performance while interacting with heterogeneous data sources as e.g., occurring in business decision making. We describe our approach which is based on inferring the user intentions from sensory inputs, providing a situation aware information assistance, and controlling the environment proactively by anticipating future goals. Our system has been realized within a smart meeting room and has in parts been evaluated. In this paper, we describe the core ideas underlying our approach and report on first findings from the evaluation.

Bernard, Jürgen; Wilhelm, Nils; Krüger, Björn; May, Thorsten; Schreck, Tobias; Kohlhammer, Jörn

MotionExplorer: Exploratory Search in Human Motion Capture Data Based on Hierarchical Aggregation

2013

IEEE Transactions on Visualization and Computer Graphics, Vol.19 (2013), 12, pp. 2257-2266

IEEE Symposium on Visual Analytics Science and Technology (VAST) <8, 2013, Atlanta, GA, USA>

We present MotionExplorer, an exploratory search and analysis system for sequences of human motion in large motion capture data collections. This special type of multivariate time series data is relevant in many research fields including medicine, sports and animation. Key tasks in working with motion data include analysis of motion states and transitions, and synthesis of motion vectors by interpolation and combination. In the practice of research and application of human motion data, challenges exist in providing visual summaries and drill-down functionality for handling large motion data collections. We find that this domain can benefit from appropriate visual retrieval and analysis support to handle these tasks in presence of large motion data.

To address this need, we developed MotionExplorer together with domain experts as an exploratory search system based on interactive aggregation and visualization of motion states as a basis for data navigation, exploration, and search. Based on an overview-first type visualization, users are able to search for interesting sub-sequences of motion based on a query-by-example metaphor, and explore search results by details on demand. We developed MotionExplorer in close collaboration with the targeted users who are researchers working on human motion synthesis and analysis, including a summative field study. Additionally, we conducted a laboratory design study to substantially improve MotionExplorer towards an intuitive, usable and robust design. MotionExplorer enables the search in human motion capture data with only a few mouse clicks. The researchers unanimously confirm that the system can efficiently support their work.

Braun, Andreas; Dutz, Tim; Alekseew, Michael; Schillinger, Philipp; Marinc, Alexander

Marker-Free Indoor Localization and Tracking of Multiple Users in Smart Environments Using a Camera-Based Approach

2013

Streitz, Norbert (Ed.) et al.: Distributed, Ambient, and Pervasive Interactions : DAPI 2013. Berlin, Heidelberg, New York: Springer, 2013. (Lecture Notes in Computer Science (LNCS) 8028), pp. 349-357

International Conference on Distributed, Ambient and Pervasive Interactions (DAPI) <1, 2013, Las Vegas, NV, USA>

In recent years, various indoor tracking and localization approaches for usage in conjunction with Pervasive Computing systems have been proposed. In a nutshell, three categories of localization methods can be identified, namely active marker-based solutions, passive marker-based solutions, and marker-free solutions. Both active and passive marker-based solutions require a person to carry some type of tagging item in order to function, which, for a multitude of reasons, makes them less favorable than marker-free solutions, which are capable of localizing persons without additional accessories. In this work, we present a marker-free, camera-based approach for use in typical indoor environments that has been designed for reliability and cost-effectiveness. We were able to successfully evaluate the system with two persons and initial tests promise the potential to increase the number of users that can be simultaneously tracked even further.

Braun, Andreas; Dutz, Tim; Kamieth, Felix

Capacitive Sensor-Based Hand Gesture Recognition in Ambient Intelligence Scenarios

2013

The University of Texas at Arlington (UTA): Proceedings of the 6th International Conference on PErvasive Technologies Related to Assistive Environments : PETRA 2013. New York: ACM, 2013, 5 p.

ACM International Conference on PErvasive Technologies Related to Assistive Environments (PETRA) <6, 2013, Rhodes Island, Greece>

Input devices based on arrays of capacitive proximity sensors allow the tracking of a user's hands in three dimensions. They can be hidden behind materials such as wood, wool or plastics without limiting their functionality, making them ideal for application in Ambient Intelligence (AmI) scenarios. Most gesture recognition frameworks are targeted towards classical input devices and interpret two-dimensional data. In this work, we present a concept for adapting classical gesture recognition methods for capacitive input devices by realizing an extension of the feature set to three dimensional input data. This allows more robust gesture recognition for free-space interaction and training specific to capacitive input devices. We have implemented this concept in a prototypical setup and tested the device in various Ambient Intelligence scenarios, ranging from manipulating home appliances to controlling multimedia applications.

Damer, Naser; Opel, Alexander; Nouak, Alexander

Performance Anchored Score Normalization for Multi-Biometric Fusion

2013

Bebis, George (Ed.) et al.: Advances in Visual Computing. 9th International Symposium, ISVC 2013 : Proceedings, Part II. Berlin, Heidelberg, New York: Springer, 2013. (Lecture Notes in Computer Science (LNCS) 8034), pp. 68-75

International Symposium on Visual Computing (ISVC) <9, 2013, Rethymnon, Crete, Greece>

This work presents a family of novel normalization techniques for score-level multi-biometric fusion. The proposed normalization is not only concerned to bring comparison scores to a common range and scale, it also focuses in bringing certain operational performance points in the distribution into alignment. The Performance Anchored Normalization (PAN) algorithms discussed here were tested on the extended Multi Modal Verification for Teleservices and Security applications database (XM2VTS) and proved to outperform conventional score normalization techniques in most tests. The tests were performed with combination fusion rules and presented as biometric verification performance measures.

Franke, Tobias; Settgast, Volker; Behr, Johannes; Raffin, Bruno

VCoRE: A Web Resource Oriented Architecture for Efficient Data Exchange

2013

Posada, Jorge (General Chair) et al.: Proceedings Web3D 2013 : 18th International Conference on 3D Web Technology. New York: ACM Press, 2013, pp. 71-78

International Conference on 3D Web Technology (WEB3D) <18, 2013, San Sebastian, Spain>

In this paper, we present a specification of a RESTful based networking interface for the efficient exchange and manipulation of visual computing resources. It is designed to include web applications by using modern web-technology such as Typed Arrays and WebSockets. The specification maps internal structures and data containers to two types, Elements and Attributes, which can be queried for a description or their content. Two modes of communication are defined, one through HTTP requests, where we use HTTP operations to manipulate Elements and Attributes or request their data in a stateless fashion, the other through WebSockets to enable a push-based communication. A key idea to this interface is that we use MIME types to specify the way data is to be exchanged in. When requesting data, the user may supply a hint or type in which the data is expected to be delivered in, which enables us to write web-applications which can process already converted data that would not have been
web-friendly before. To have such a mode of operation, we also present a table of extracted basic data types usable for requesting data conversion, which are derived from the Typed Array specification and shared across shader languages.

Große-Puppendahl, Tobias; Berghöfer, Yannick; Braun, Andreas; Wimmer, Raphael; Kuijper, Arjan

OpenCapSense: A Rapid Prototyping Toolkit for Pervasive Interaction Using Capacitive Sensing

2013

IEEE International Conference on Pervasive Computing and Communications. Proceedings : PerCom 2013. Los Alamitos, Calif.: IEEE Computer Society Press, 2013, pp. 151-158

International Conference on Pervasive Computing and Communications (PerCom) <11, 2013, San Diego, CA, USA>

Capacitive sensing allows the creation of unobtrusive user interfaces that are based on measuring the proximity to objects or recognizing their dielectric properties. Combining the data of many sensors, applications such as in-the-air gesture recognition, location tracking or fluid-level sensing can be realized. We present OpenCapSense, a highly flexible opensource toolkit that enables researchers to implement new types of pervasive user interfaces with low effort. The toolkit offers a high temporal resolution with sensor update rates up to 1 kHz. The typical spatial resolution varies between one millimeter at close object proximity and around one centimeter at distances of 35 cm or above.

Große-Puppendahl, Tobias; Braun, Andreas; Kamieth, Felix; Kuijper, Arjan

Swiss-Cheese Extended: An Object Recognition Method for Ubiquitous Interfaces based on Capacitive Proximity Sensing

2013

Bodker, Susanne (Ed.) et al.: CHI 2013. Changing Perspective : The 31st Annual CHI Conference on Human Factors in Computing Systems. New York: ACM Press, 2013, pp. 1401-1410

Conference on Human Factors in Computing Systems (CHI) <31, 2013, Paris, France>

Swiss-Cheese Extended proposes a novel real-time method for recognizing objects with capacitive proximity sensors. Applying this technique to ubiquitous user interfaces, it is possible to detect the 3D-position of multiple human hands in different configurations above a surface that is equipped with a small number of sensors. The retrieved object configurations can significantly improve a user's interaction experience or an application's execution context, for example by detecting multi-hand zoom and rotation gestures or recognizing a grasping hand. We emphasize the broad applicability of the proposed method with a study of a multi-hand gesture recognition device. Swiss-Cheese Extended proposes a novel real-time method for recognizing objects with capacitive proximity sensors. Applying this technique to ubiquitous user interfaces, it is possible to detect the 3D-position of multiple human hands in different configurations above a surface that is equipped with a small number of
sensors. The retrieved object configurations can significantly improve a user's interaction experience or an application's execution context, for example by detecting multi-hand zoom and rotation gestures or recognizing a grasping hand. We emphasize the broad applicability of the proposed method with a study of a multi-hand gesture recognition device.

Hammon, Matthias; Cavallaro, Alexander; Erdt, Marius; Dankerl, Peter; Kirschner, Matthias; Drechsler, Klaus; Wesarg, Stefan; Uder, Michael; Janka, Rolf

Model-Based Pancreas Segmentation in Portal Venous Phase Contrast-Enhanced CT Images

2014

Journal of Digital Imaging, Vol.26 (2014), 6, pp. 1082-1090. First published online 08 March 2013

This study aims to automatically detect and segment the pancreas in portal venous phase contrast-enhanced computed tomography (CT) images. The institutional review board of the University of Erlangen-Nuremberg approved this study and waived the need for informed consent. Discriminative learning is used to build a pancreas tissue classifier incorporating spatial relationships between the pancreas and surrounding organs and vessels. Furthermore, discrete cosine and wavelet transforms are used to build texture features to describe local tissue appearance. Classification is used to guide a constrained statistical shape model to fit the data.

The algorithm to detect and segment the pancreas was evaluated on 40 consecutive CT data that were acquired in the portal venous contrast agent phase. Manual segmentation of the pancreas was carried out by experienced radiologists and served as reference standard. Threefold cross validation was performed. The algorithm-based detection and segmentation yielded an average surface distance of 1.7 mm and an average overlap of 61.2 % compared with the reference standard. The overall runtime of the system was 20.4 min. The presented novel approach enables automatic pancreas segmentation in portal venous phase contrast-enhanced CT images which are included in almost every clinical routine abdominal CT examination. Reliable pancreatic segmentation is crucial for computer-aided detection systems and an organ-specific decision support.

Havemann, Sven; Edelsbrunner, Johannes; Wagner, Philipp; Fellner, Dieter W.

Curvature-Controlled Curve Editing Using Piecewise Clothoid Curves

2013

Computers & Graphics, Vol.37 (2013), 6, pp. 764-773

International Conference on Shape Modeling and Applications (SMI) <15, 2013, Bournemouth, UK>

Two-dimensional curves are conventionally designed using splines or Bézier curves. Although formally they are C² or higher, the variation of the curvature of (piecewise) polynomial curves is difficult to control; in some cases it is practically impossible to obtain the desired curvature. As an alternative we propose piecewise clothoid curves (PCCs). We show that from the design point of view they have many advantages: control points are interpolated, curvature extrema lie in the control points, and adding control points does not change the curve. We present a fast localized clothoid interpolation algorithm that can also be used for curvature smoothing, for curve fitting, for curvature blending, and even for directly editing the curvature. We give a physical interpretation of variational curvature minimization, from which we derive our scheme. Finally, we demonstrate the achievable quality with a range of examples.

Henke, Birgit; Vahl, Matthias; Zhou, Zhiliang

Removing Color Cast of Underwater Images through Non-Constant Color Constancy Hypothesis

2013

Loncaric, Sven (Ed.) et al.: ISPA 2013 : 8th International Symposium on Image and Signal Processing and Analysis, pp. 20-24

International Symposium on Image and Signal Processing and Analysis (ISPA) <8, 2013, Trieste, Italy>

Color cast is a crucial problem for color image processing. White balance has been widely used to eliminate color cast to improve the image's quality. Most of white balance implementations are based on color constancy hypothesis. A wellknown color constancy hypothesis is given in [1], unifying White Patch [2], Grey World [3], Shades of Grey [4], and Grey Edge [1] assumptions in one expression. However, this general hypothesis works on underwater images not as reliable as on common images. In the color constancy hypothesis for common scenes, the ambient light source is spatial constant. But in underwater scenes, the light suffers from serious attenuation, especially in the red part of the visible spectrum. This attenuation causes spatial variance of the ambient light source, which lets classic color constancy hypothesis fail. In this paper, we propose a novel low-level image feature-based color constancy hypothesis for underwater scenes. Based on this hypothesis, we propose an
algorithm, using a distance map to estimate multiple gain factors to remove the color cast.

Henniger, Olaf; Nikolov, Dimitar

Extending EMV Payment Smart Cards with Biometric On-Card Verification

2013

Fischer-Hübner, Simone (Ed.) et al.: Policies and Research in Identity Management : Third IFIP WG 11.6 Working Conference, IDMAN 2013. Proceedings. Berlin, Heidelberg, New York: Springer, 2013. (IFIP Advances in Information and Communication Technology 396), pp. 121-130

IFIP WG 11.6 Working Conference on Policies & Research in Identity Management (IDMAN) <3, 2013, London, UK>

Nowadays, many bank cards are smart cards (i.e. integrated-circuit cards) based on the EMV specifications for payment systems. This paper specifies how biometric on-card verification can be integrated into EMV debit and credit cards in a backwards-compatible way. The biometric verification does not change the EMV transaction flow outside the cardholder-verification step. The proposed payment system has been prototyped using Java cards and an applet for handwritten signature on-card verification.

Kahn, Svenja; Bockholt, Ulrich; Kuijper, Arjan; Fellner, Dieter W.

Towards Precise Real-Time 3D Difference Detection for Industrial Applications

2013

Computers in Industry, Vol.64 (2013), 9, pp. 1115-1128

3D difference detection is the task to verify whether the 3D geometry of a real object exactly corresponds to a 3D model of this object. We present an approach for 3D difference detection with a hand-held depth camera. In contrast to previous approaches, with the presented approach geometric differences can be detected in real-time and from arbitrary viewpoints. The 3D difference detection accuracy is improved by two approaches: first, the precision of the depth camera's pose estimation is improved by coupling the depth camera with a high precision industrial measurement arm. Second, the influence of the depth measurement noise is reduced by integrating a 3D surface reconstruction algorithm. The effects of both enhancements are quantified by a ground-truth based quantitative evaluation, both for a time-of-flight (SwissRanger 4000) and a structured light depth camera (Kinect). With the proposed enhancements, differences of few millimeters can be detected from 1 m measurement
distance.

Kahn, Svenja; Keil, Jens; Müller, Benedikt; Bockholt, Ulrich; Fellner, Dieter W.

Capturing of Contemporary Dance for Preservation and Presentation of Choreographies in Online Scores

2013

2013 Digital Heritage International Congress. Volume 1 : DigitalHeritage. New York: The Institute of Electrical and Electronics Engineers (IEEE), 2013, pp. 273-280

Digital Heritage International Congress (DigitalHeritage) <2013, Marseille, France>

In this paper, we present a generic and affordable approach for an automatized and markerless capturing of movements in dance, which was developed in the Motion Bank / The Forsythe Company project (www.motionbank.org). Thereby within Motion Bank we are considering the complete digitalization workflow starting with the setup of the camera array and ending with a web-based presentation of "Online Scores" visualizing different elements of choreography. Within our project, we have used our technology in two modern dance projects, one "Large Motion Space Performance" covering a large stage in solos and trios and one "Restricted Motion Space Performance" that is suited to be captured with range cameras. The project is realized in close cooperation with different choreographers and dance companies of modern ballet and with multi-media artists forming the visual representations of dance.

Keil, Jens; Pujol, Laia; Roussou, Maria; Engelke, Timo; Schmitt, Michael; Bockholt, Ulrich; Eleftheratou, Stamatia

A Digital Look at Physical Museum Exhibits: Designing Personalized Stories with Handheld Augmented Reality in Museums

2013

2013 Digital Heritage International Congress. Volume 2 : DigitalHeritage. New York: The Institute of Electrical and Electronics Engineers (IEEE), 2013, pp. 685-688

Digital Heritage International Congress (DigitalHeritage) <2013, Marseille, France>

In this paper we present the design of handheld Augmented Reality (AR) experiences that are seamlessly incorporated into interactive museum narratives, specifically for the Acropolis Museum. The experiences start by forming a visitor profile that later dynamically adapts the narrative, including the AR activities, to the user's behaviour. In this cohesive narrative context, the AR activities provide four ways to digitally look at the exhibits: virtual reconstruction of the original aspect; placement in the original location; visual highlighting of interesting details and annotations; and recreation of mythological appearances. The challenges of this design are presented, concluding with a discussion and lessons learned.

Keil, Matthias; Kaisler, Alexander; Oyarzun Laura, Cristina; Wesarg, Stefan

Refinement and Expansion of Matched Vessel Graphs for Intraoperative Deformable Registration of Hepatic CT and Ultrasound

2013

Holmes III, David R. (Ed.) et al.: Medical Imaging 2013: Image-Guided Procedures, Robotic Interventions, and Modeling : Progress in Biomedical Optics and Imaging. Proceedings Issue. Vol. 14, No. 38. Bellingham: SPIE Press, 2013. (Proceedings of SPIE 8671), pp. 867107-1 - 867107-10

SPIE Medical Imaging Symposium <2013, Lake Buena Vista, FL, USA>

Multimodal registration of intraoperative ultrasound and preoperative contrast enhanced computed tomography (CT) imaging is the basis for image guided percutaneous hepatic interventions. Currently, the surgeon manually performs a rigid registration using vessel structures and other anatomical landmarks for visual guidance.

We have previously presented our approach for an automation of this intraoperative registration step based on the definition of bijective correspondences between the vessel structures using an automatic graph matching.¹

This paper describes our method for refinement and expansion of the matched vessel graphs, resulting in a high number of bijective correspondences. Based on these landmarks, we could extend our method to a fully deformable registration. Our system was applied successfully on CT and ultrasound data of nine patients, which are studied in this paper. The number of corresponding vessel points could be raised from a mean of 9.6 points after the graph matching to 70.2 points using the presented refinement method. This allows for the computation of a smooth deformation field. Furthermore, we can show that our deformation calculation raises the registration accuracy for 3 of the 4 chosen target vessels in pre-/postoperative CT with a mean accuracy improvement of 44%.

Kopf, Johannes; Langguth, Fabian; Scharstein, Daniel; Szeliski, Richard; Goesele, Michael

Image-Based Rendering in the Gradient Domain

2013

ACM Transactions on Graphics, Vol.32 (2013), 6, pp. 199:1 - 199:9

Conference on Computer and Exhibition on Computer Graphics and Interactive Techniques in Asia (SIGGRAPH ASIA) <6, 2013, Hong Kong, China>

We propose a novel image-based rendering algorithm for handling complex scenes that may include reflective surfaces. Our key contribution lies in treating the problem in the gradient domain. We use a standard technique to estimate scene depth, but assign depths to image gradients rather than pixels. A novel view is obtained by rendering the horizontal and vertical gradients, from which the final result is reconstructed through Poisson integration using an approximate solution as a data term. Our algorithm is able to handle general scenes including reflections and similar effects without explicitly separating the scene into reflective and transmissive parts, as required by previous work. Our prototype renderer is fully implemented on the GPU and runs in real time on commodity hardware.

Krämer, Michel; Ludlow, David; Khan, Zaheer

Domain-Specific Languages for Agile Urban Policy Modelling

2013

Rekdalsbakken, Webjørn (Ed.) et al.: ECMS 2013 : 27th European Conference on Modelling and Simulation, pp. 673-680

European Conference on Modelling and Simulation (ECMS) <27, 2013, Ålesund, Norway>

In this paper we present a new approach of performing urban policy modelling and making with the help of ICT enabled tools. We present a complete policy cycle that includes creating policy plans, securing stakeholders and public engagement, implementation, monitoring, and evaluating a particular policy model. ICT enabled tools can be deployed at various stages in this cycle, but they require an intuitive interface which can be supported by domain-specific languages (DSLs) as the means to express policy modelling aspects such as computational processes and computer-readable policy rules in the words of the domain expert. In order to evaluate the use of such languages, we present a real-world scenario from the urbanAPI project. We describe how DSLs for this scenario would look like. Finally, we discuss strengths and limitations of our approach as well as lessons learnt.

Landesberger, Tatiana von; Diel, Simon; Bremm, Sebastian; Fellner, Dieter W.

Visual Analysis of Contagion in Networks

2015

Information Visualization, Vol.14 (2015), 2, pp. 93-110. Published online before print May 28, 2013

Contagion is a process whereby the collapse of a node in a network leads to the collapse of neighboring nodes and thereby sets off a chain reaction in the network. It thus creates a special type of time-dependent network. Such processes are studied in various applications, for example, in financial network analysis, infection diffusion prediction, supply-chain management, or gene regulation. Visual analytics methods can help analysts examine contagion effects. For this purpose, network visualizations need to be complemented with specific features to illustrate the contagion process. Moreover, new visual analysis techniques for comparison of contagion need to be developed.

In this paper, we propose a system geared to the visual analysis of contagion. It includes the simulation of contagion effects as well as their visual exploration. We present new tools able to compare the evolution of the different contagion processes. In this way, propagation of disturbances can be effectively analyzed. We focus on financial networks; however, our system can be applied to other use cases as well.

Li, Bo; Godil, Afzal; Johan, Henry

Hybrid Shape Descriptor and Meta Similarity Generation for Non-rigid and Partial 3D Model Retrieval

2014

Multimedia Tools and Applications, Vol.72 (2014), 2, pp. 1531-1560. First published online 23 April 2013

Non-rigid and partial 3D model retrieval are two significant and challenging research directions in the field of 3D model retrieval. Little work has been done in proposing a hybrid shape descriptor that works for both retrieval scenarios, let alone the integration of the component features of the hybrid shape descriptor in an automatic way. In this paper, we propose a hybrid shape descriptor that integrates both geodesic distance-based global features and curvature-based local features. We also develop an automatic algorithm to generate meta similarity resulting from different component features of the hybrid shape descriptor based on Particle Swarm Optimization. Experimental results demonstrate the effectiveness and advantages of our framework, as well as the significant improvements in retrieval performances. The framework is general and can be applied to similar approaches that integrate more features for the development of a single algorithm for both non-rigid and partial 3D
model retrieval.

Limper, Max; Jung, Yvonne; Behr, Johannes; Alexa, Marc

The POP Buffer: Rapid Progressive Clustering by Geometry Quantization

2013

Computer Graphics Forum, Vol.32 (2013), 7, pp. 197-206

Pacific Conference on Computer Graphics and Applications (PG) <21, 2013, Singapore>

Within this paper, we present a novel, straightforward progressive encoding scheme for general triangle soups, which is particularly well-suited for mobile and Web-based environments due to its minimal requirements on the client's hardware and software. Our rapid encoding method uses a hierarchy of quantization to effectively reorder the original primitive data into several nested levels of detail. The resulting stateless buffer can progressively be transferred as-is to the GPU, where clustering is efficiently performed in parallel during rendering. We combine our approach with a crack-free mesh partitioning scheme to obtain a straightforward method for fast streaming and basic view-dependent LOD control.

Limper, Max; Jung, Yvonne; Behr, Johannes; Sturm, Timo; Franke, Tobias; Schwenk, Karsten; Kuijper, Arjan

Fast, Progressive Loading of Binary-Encoded Declarative-3D Web Content

2013

IEEE Computer Graphics and Applications, Vol.33 (2013), 5, pp. 26-36

The encoding of scene-graph related structured data along with unstructured vertex data within the same descriptive elements of a scene is a major drawback of XML based model formats (such as X3D or Collada) and declarative 3D approaches. Web browsers have to download the complete scene before being able to further process the structure of the document. By introducing Sequential Image Geometry (SIG) containers and explicit binary containers we were able to overcome this limitation. They are wellaligned to buffer structures on the GPU, enabling fast decoding and GPU upload. We improve the image-based approach significantly and introduce a new method called Progressive Binary Geometry (PBG) which enables a simple yet highly progressive transmission of arbitrary mesh data.

Liu, Yisi; Sourina, Olga

EEG Databases for Emotion Recognition

2013

Mao, Xiaoyang (Ed.) et al.: 2013 International Conference on Cyberworlds : Cyberworlds 2013. Los Alamitos, Calif.: IEEE Computer Society Conference Publishing Services (CPS), 2013, pp. 302-309

International Conference on Cyberworlds (CW) <12, 2013, Yokohama, Japan>

Emotion recognition from Electroencephalogram (EEG) rapidly gains interest from research community. Two affective EEG databases are presented in this paper. Two experiments are conducted to set up the databases. Audio and visual stimuli are used to evoke emotions during the experiments. The stimuli are selected from IADS and IAPS databases. 14 subjects participated in each experiment. Emotiv EEG device is used for the data recording. The EEG data are rated by the participants with arousal, valence, and dominance levels. The correlation between powers of different EEG bands and the affective ratings is studied.

The results agree with the literature findings and analyses of benchmark DEAP database that proves the reliability of the two databases. Similar brain patterns of emotions are obtained between the established databases and the benchmark database. A SVM-based emotion recognition algorithm is proposed and applied to both databases and the benchmark database. Use of a Fractal Dimension feature in combination with statistical and Higher Order Crossings (HOC) features gives us results with the best accuracy. Up to 8 emotions can be recognized. The accuracy is consistent between the established databases and the benchmark database.

Milan, Anton; Schindler, Konrad; Roth, Stefan

Detection- and Trajectory-Level Exclusion in Multiple Object Tracking

2013

IEEE Computer Society: IEEE Conference on Computer Vision and Pattern Recognition. Proceedings : CVPR 2013. Los Alamitos, Calif.: IEEE Computer Society Conference Publishing Services (CPS), 2013, pp. 3682-3689

IEEE Conference on Computer Vision and Pattern Recognition (CVPR) <31, 2013, Portland, OR, USA>

When tracking multiple targets in crowded scenarios, modeling mutual exclusion between distinct targets becomes important at two levels: (1) in data association, each target observation should support at most one trajectory and each trajectory should be assigned at most one observation per frame; (2) in trajectory estimation, two trajectories should remain spatially separated at all times to avoid collisions. Yet, existing trackers often sidestep these important constraints. We address this using a mixed discrete-continuous conditional random field (CRF) that explicitly models both types of constraints: Exclusion between conflicting observations with supermodular pairwise terms, and exclusion between trajectories by generalizing global label costs to suppress the co-occurrence of incompatible labels (trajectories). We develop an expansion move-based MAP estimation scheme that handles both non-submodular constraints and pairwise global label costs. Furthermore, we perform a
statistical analysis of ground-truth trajectories to derive appropriate CRF potentials for modeling data fidelity, target dynamics, and inter-target occlusion.

Nazemi, Kawa; Retz, Reimond; Bernard, Jürgen; Kohlhammer, Jörn; Fellner, Dieter W.

Adaptive Semantic Visualization for Bibliographic Entries

2013

Bebis, George (Ed.) et al.: Advances in Visual Computing. 9th International Symposium, ISVC 2013 : Proceedings, Part II. Berlin, Heidelberg, New York: Springer, 2013. (Lecture Notes in Computer Science (LNCS) 8034), pp. 13-24

International Symposium on Visual Computing (ISVC) <9, 2013, Rethymnon, Crete, Greece>

Adaptive visualizations aim to reduce the complexity of visual representations and convey information using interactive visualizations. Although the research on adaptive visualizations grew in the last years, the existing approaches do not make use of the variety of adaptable visual variables. Further the existing approaches often premises experts, who has to model the initial visualization design. In addition, current approaches either incorporate user behavior or data types. A combination of both is not proposed to our knowledge.

This paper introduces the instantiation of our previously proposed model that combines both: involving different influencing factors for and adapting various levels of visual peculiarities, on visual layout and visual presentation in a multiple visualization environment. Based on data type and users' behavior, our system adapts a set of applicable visualization types. Moreover, retinal variables of each visualization type are adapted to meet individual or canonic requirements on both, data types and users' behavior. Our system does not require an initial expert modeling.

Scherer, Maximilian; Landesberger, Tatiana von; Schreck, Tobias

Visual-interactive Querying for Multivariate Research Data Repositories using Bag-of-words

2013

Association for Computing Machinery (ACM): JCDL 2013. Proceedings : 13th ACM/IEEE-CS Joint Conference on Digital Libraries. New York: ACM, 2013, pp. 285-294

ACM/IEEE-CS Joint Conference on Digital Libraries (JCDL) <13, 2013, Indianapolis, IN, USA>

Large amounts of multivariate data are collected in different areas of scientific research and industrial production. These data are collected, archived and made publicly available by research data repositories. In addition to meta-data based access, content-based approaches are highly desirable to effectively retrieve, discover and analyze data sets of interest. Several such methods, that allow users to search for particular curve progressions, have been proposed. However, a major challenge when providing content-based access - interactive feedback during query formulation - has not received much attention yet. This is important because it can substantially improve the user's search effectiveness.

In this paper, we present a novel interactive feedback approach for content-based access to multivariate research data. Thereby, we enable query modalities that were not available for multivariate data before. We provide instant search results and highlight query patterns in the result set. Real-time search suggestions give an overview of important patterns to look for in the data repository. For this purpose, we develop a bag-of-words index for multivariate data as the back-end of our approach.

We apply our method to a large repository of multivariate data from the climate research domain. We describe a use-case for the discovery of interesting patterns in maritime climate research using our new visual-interactive query tools.

Schmidt, Uwe; Rother, Carsten; Nowozin, Sebastian; Jancsary, Jeremy; Roth, Stefan

Discriminative Non-blind Deblurring

2013

IEEE Computer Society: IEEE Conference on Computer Vision and Pattern Recognition. Proceedings : CVPR 2013. Los Alamitos, Calif.: IEEE Computer Society Conference Publishing Services (CPS), 2013, pp. 604-611

IEEE Conference on Computer Vision and Pattern Recognition (CVPR) <31, 2013, Portland, OR, USA>

Non-blind deblurring is an integral component of blind approaches for removing image blur due to camera shake. Even though learning-based deblurring methods exist, they have been limited to the generative case and are computationally expensive. To this date, manually-defined models are thus most widely used, though limiting the attained restoration quality. We address this gap by proposing a discriminative approach for non-blind deblurring. One key challenge is that the blur kernel in use at test time is not known in advance. To address this, we analyze existing approaches that use half-quadratic regularization. From this analysis, we derive a discriminative model cascade for image deblurring. Our cascade model consists of a Gaussian CRF at each stage, based on the recently introduced regression tree fields. We train our model by loss minimization and use synthetically generated blur kernels to generate training data. Our experiments show that the proposed approach is efficient
and yields state-of-the-art restoration quality on images corrupted with synthetic and real blur.

Schmitt, Nikolas; Knuth, Martin; Bender, Jan; Kuijper, Arjan

Multilevel Cloth Simulation using GPU Surface Sampling

2013

Bender, Jan (Ed.) et al.: VRIPHYS 13: 10th Workshop in Virtual Reality Interactions and Physical Simulations. Goslar: Eurographics Association, 2013, pp. 1-10

International Workshop in Virtual Reality Interaction and Physical Simulations (VRIPhys) <10, 2013, Lille, France>

Today most cloth simulation systems use triangular mesh models. However, regular grids allow many optimizations as connectivity is implicit, warp and weft directions of the cloth are aligned to grid edges and distances between particles are equal. In this paper we introduce a cloth simulation that combines both model types. All operations that are performed on the CPU use a low-resolution triangle mesh while GPU-based methods are performed efficiently on a high-resolution grid representation. Both models are coupled by a sampling operation which renders triangle vertex data into a texture and by a corresponding projection of texel data onto a mesh. The presented scheme is very flexible and allows individual components to be performed on different architectures, data representations and detail levels. The results are combined using shader programs which causes a negligible overhead. We have implemented CPU-based collision handling and a GPU-based hierarchical constraint solver to
simulate systems with more than 230k particles in real-time.

Steger, Sebastian; Bozoglu, Y. Nazli; Kuijper, Arjan; Wesarg, Stefan

Application of Radial Ray Based Segmentation to Cervical Lymph Nodes in CT Images

2013

IEEE Transactions on Medical Imagaing, Vol.32 (2013), 5, pp. 888-900

The 3D-segmentation of lymph nodes in CT images is required for staging and disease progression monitoring. Major challenges are shape and size variance, as well as low contrast, image noise, and pathologies.

In this paper, radial ray based segmentation is applied to lymph nodes: From a seed point, rays are cast into all directions and an optimization technique determines a radius for each ray based on image appearance and shape knowledge. Lymph node specific appearance cost functions are introduced and their optimal parameters are determined. For the first time, the resulting segmentation accuracy of different appearance cost functions and optimization strategies are compared. Further contributions are extensions to reduce the dependency on the seed point, to support a larger variety of shapes, and to enable interaction. The best results are obtained using graph-cut on a combination of the direction weighted image gradient and accumulated intensities outside a predefined intensity range. Evaluation on 100 lymph nodes shows that with an average symmetric surface distance of 0.41 mm the segmentation accuracy is close to manual segmentation and outperforms existing radial ray and model based
methods. The method's inter-observer-variability of 5.9% for volume assessment is lower than the 15.9% obtained using manual segmentation.

Steger, Teena; Hoßbach, Martin; Wesarg, Stefan

Marker Detection Evaluation by Phantom and Cadaver Experiments for C-arm Pose Estimation Pattern

2013

Holmes III, David R. (Ed.) et al.: Medical Imaging 2013: Image-Guided Procedures, Robotic Interventions, and Modeling : Progress in Biomedical Optics and Imaging. Proceedings Issue. Vol. 14, No. 38. Bellingham: SPIE Press, 2013. (Proceedings of SPIE 8671), pp. 86711V-1 - 86711V-9

SPIE Medical Imaging Symposium <2013, Lake Buena Vista, FL, USA>

C-arm fluoroscopy is used for guidance during several clinical exams, e.g. in bronchoscopy to locate the bronchoscope inside the airways. Unfortunately, these images provide only 2D information. However, if the C-arm pose is known, it can be used to overlay the intrainterventional fluoroscopy images with 3D visualizations of airways, acquired from preinterventional CT images. Thus, the physician's view is enhanced and localization of the instrument at the correct position inside the bronchial tree is facilitated.

We present a novel method for C-arm pose estimation introducing a marker-based pattern, which is placed on the patient table. The steel markers form a pattern, allowing to deduce the C-arm pose by use of the projective invariant cross-ratio. Simulations show that the C-arm pose estimation is reliable and accurate for translations inside an imaging area of 30 cm x 50 cm and rotations up to 30°. Mean error values are 0.33 mm in 3D space and 0.48 px in the 2D imaging plane. First tests on C-arm images resulted in similarly compelling accuracy values and high reliability in an imaging area of 30 cm x 42.5 cm. Even in the presence of interfering structures, tested both with anatomy phantoms and a turkey cadaver, high success rates over 90% and fully satisfying execution times below 4 sec for 1024 px × 1024 px images could be achieved.

Steiger, Martin; Lücke-Tieke, Hendrik; May, Thorsten; Kuijper, Arjan; Kohlhammer, Jörn

Using Layout Stitching to Create Deterministic Local Graph Layouts

2013

Oliveira, Manuel M. (Ed.) et al.: WSCG 2013. Full Papers. Proceedings : The 21st International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision. Plzen: University of West Bohemia, 2013, pp. 1-9

International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision (WSCG) <21, 2013, Plzen, Czech Republic>

Dynamic graph layouts are often used to position nodes in local views of large graphs. These layouts can be optimized to minimize changes when navigating to other parts of the graph. Dynamic graph layout techniques do not, however, guarantee that a local layout is recognizable when the user visits the same area twice. In this paper we present a method to create stable and deterministic layouts of dynamic views of large graphs. It is based on a well-known panorama-stitching algorithm from the image processing domain. Given a set of overlapping photographs it creates a larger panorama that combines the original images. In analogy to that our algorithm stitches pre-computed layouts of subgraphs to form a larger, single layout. This deterministic approach makes structures and node locations persistent which creates identical visual representations of the graph. This enables the user to recognize previously encountered parts and to decide whether a certain part of a dataset has
already been explored before or not.

Thaller, Wolfgang; Krispel, Ulrich; Zmugg, René; Havemann, Sven; Fellner, Dieter W.

Shape Grammars on Convex Polyhedra

2013

Computers & Graphics, Vol.37 (2013), 6, pp. 707-717

International Conference on Shape Modeling and Applications (SMI) <15, 2013, Bournemouth, UK>

Shape grammars are the method of choice for procedural modeling of architecture. State of the art shape grammar systems define a bounding box for each shape; various operations can then be applied based on this bounding box. Most notably, the box can be split into smaller boxes along any of its three axes. We argue that a greater variety can be obtained by using convex polyhedra as bounding volumes instead. Split operations on convex polyhedra are no longer limited to the three principal axes but can use arbitrary planes. Such splits permit a volumetric decomposition into convex elements; as convex polyhedra can represent many shapes more faithfully than boxes, shape grammar rules can adapt to a much wider array of different contexts. We generalize established shape operations and introduce new operations that now become possible.

Ullrich, Torsten; Schinko, Christoph; Schiffer, Thomas; Fellner, Dieter W.

Procedural Descriptions for Analyzing Digitized Artifacts

2013

Applied Geomatics, Vol.5 (2013), 3, pp. 185-192

Within the last few years, generative modeling techniques have gained attention especially in the context of cultural heritage. As a generative model describes a rather ideal object than a real one, generative techniques are a basis for object description and classification. This procedural knowledge differs from other kinds of knowledge, such as declarative knowledge, in a significant way: It is an algorithm, which reflects the way objects are designed. Consequently, generative models are not a replacement for established geometry descriptions (based on points, triangles, etc.) but a semantic enrichment. In combination with variance analysis techniques, generative descriptions can be used to validate reconstructions. Detailed mesh comparisons can reveal smallest changes and damages. These analysis and documentation tasks are needed not only in the context of cultural heritage but also in engineering and manufacturing.

Our contribution to this problem is a work flow, which automatically combines generative/procedural descriptions with reconstructed artifacts and performs a nominal/actual value comparison. The reference surface is a procedural model whose accuracy and systematics describe the semantic properties of an object, whereas the actual object is a real-world data set (laser scan or photogrammetric reconstruction) without any additional semantic information.

Ullrich, Torsten; Silva, Nelson; Eggeling, Eva; Fellner, Dieter W.

Generative Modeling and Numerical Optimization for Energy Efficient Buildings

2013

IEEE Industrials Electronics Society: IECON 2013 - 39th Annual Conference of the IEEE Industrial Electronics Society. Proceedings. New York: IEEE Press, 2013, pp. 4756-4761

Annual Conference of the IEEE Industrial Electronics Society (IECON) <39, 2013, Vienna, Austria>

A procedural model is a script, which generates a geometric object. The script's input parameters offer a simple way to specify and modify the scripting output. Due to its algorithmic character, a procedural model is perfectly suited to describe geometric shapes with well-organized structures and repetitive forms.

In this paper, we interpret a generative script as a function, which is nested into an objective function. Thus, the script's parameters can be optimized according to an objective. We demonstrate this approach using architectural examples: each generative script creates a building with several free parameters. The objective function is an energy-efficiency-simulation that approximates a building's annual energy consumption. Consequently, the nested objective function reads a set of building parameters and returns the energy needs for the corresponding building. This nested function is passed to a minimization and optimization process. Outcome is the best building (within the family of buildings described by its script) concerning energy-efficiency. Our contribution is a new way of modeling. The generative approach separates design and engineering: the complete design is encoded in a script and the script ensures that all parameter combinations (within a fixed range) generate a valid
design. Then the design can be optimized numerically.

Weber, Daniel; Bender, Jan; Schnös, Markus; Stork, André; Fellner, Dieter W.

Efficient GPU Data Structures and Methods to Solve Sparse Linear Systems in Dynamics Applications

2013

Computer Graphics Forum, Vol.32 (2013), 1, pp. 16-26

We present graphics processing unit (GPU) data structures and algorithms to efficiently solve sparse linear systems that are typically required in simulations of multi-body systems and deformable bodies. Thereby, we introduce an efficient sparse matrix data structure that can handle arbitrary sparsity patterns and outperforms current state-of-the-art implementations for sparse matrix vector multiplication. Moreover, an efficient method to construct global matrices on the GPU is presented where hundreds of thousands of individual element contributions are assembled in a few milliseconds. A finite-element-based method for the simulation of deformable solids as well as an impulse-based method for rigid bodies are introduced in order to demonstrate the advantages of the novel data structures and algorithms. These applications share the characteristic that a major computational effort consists of building and solving systems of linear equations in every time step. Our solving method
results in a speed-up factor of up to 13 in comparison to other GPU methods.

Widmer, Sven; Wodniok, Dominik; Weber, Nicolas; Goesele, Michael

Fast Dynamic Memory Allocator for Massively Parallel Architectures

2013

Cavazos, John (Ed.) et al.: Proceedings of the 6th Workshop on General Purpose Processor Using Graphics Processing Units : GPGPU-6. New York: ACM, 2013, pp. 120-126

Annual Workshop on General Purpose Processing Using Graphics Processors (GPGPU) <6, 2013, Houston, TX, USA>

Dynamic memory allocation in massively parallel systems often suffers from drastic performance decreases due to the required global synchronization. This is especially true when many allocation or deallocation requests occur in parallel. We propose a method to alleviate this problem by making use of the SIMD parallelism found in most current massively parallel hardware. More specifically, we propose a hybrid dynamic memory allocator operating at the SIMD parallel warp level. Using additional constraints that can be fulfilled for a large class of practically relevant algorithms and hardware systems we are able to significantly speed-up the dynamic allocation. We present and evaluate a prototypical implementation for modern CUDA-enabled graphics cards, achieving an overall speedup of up to several orders of magnitude.

Wientapper, Folker; Wuest, Harald; Rojtberg, Pavel; Fellner, Dieter W.

A Camera-Based Calibration for Automotive Augmented Reality Head-Up-Displays

2013

IEEE Computer Society Visualization and Graphics Technical Committee (VGTC): 12th IEEE International Symposium on Mixed and Augmented Reality 2013. : ISMAR 2013. Los Alamitos, Calif.: IEEE Computer Society, 2013, pp. 189-197

IEEE International Symposium on Mixed and Augmented Reality (ISMAR) <12, 2013, Adelaide, SA, Australia>

Using Head-up-Displays (HUD) for Augmented Reality requires to have an accurate internal model of the image generation process, so that 3D content can be visualized perspectively correct from the viewpoint of the user. We present a generic and cost-effective camera-based calibration for an automotive HUD which uses the windshield as a combiner. Our proposed calibration model encompasses the view-independent spatial geometry, i.e. the exact location, orientation and scaling of the virtual plane, and a view-dependent image warping transformation for correcting the distortions caused by the optics and the irregularly curved windshield. View-dependency is achieved by extending the classical polynomial distortion model for cameras and projectors to a generic five-variate mapping with the head position of the viewer as additional input. The calibration involves the capturing of an image sequence from varying viewpoints, while displaying a known target pattern on the HUD. The accurate
registration of the camera path is retrieved with state-of-the-art vision-based tracking. As all necessary data is acquired directly from the images, no external tracking equipment needs to be installed. After calibration, the HUD can be used together with a head-tracker to form a head-coupled display which ensures a perspectively correct rendering of any 3D object in vehicle coordinates from a large range of possible viewpoints. We evaluate the accuracy of our model quantitatively and qualitatively.

Wächter, Michael; Jäger, Kathrin; Thürck, Daniel; Weissgraeber, Stephanie; Widmer, Sven; Goesele, Michael; Hamacher, Kay

Using Graphics Processing Units to Investigate Molecular Coevolution

2014

Concurrency and Computation, Vol.26 (2014), 6, pp. 1278-1296. First published online 26 June 2013

Interntional Emerging Computational Methods for the Life Sciences Workshop (ECMLS) <3, 2012, Delft, Netherlands>

We present a massively parallel implementation of the computation of (co)evolutionary signals from biomolecular sequence alignments based on mutual information (MI) and a normalization procedure to neutral evolution. The MI is computed for two-point and three-point correlations within any multiple sequence alignment. We meet the high computational demand in the normalization procedure efficiently with an implementation on Graphics Processing Units (GPUs) using NVIDIA's CUDA framework.

In particular, the normalization of the MI for three-point 'cliques' of amino acids or nucleotides requires large sampling numbers in the normalization, which we achieve by using GPUs. GPU computation serves as an enabling technology here insofar as MI normalization is also possible using traditional computational methods [1] or cluster computation, but only GPU computation makes MI normalization for sequence analysis feasible in a statistically sufficient sample and in acceptable time given affordable commodity hardware. We illustrate (i) the computational efficiency and (ii) the biological usefulness of two-point and three-point MI by applications to the well-known protein calmodulin and the variable surface glycoprotein (VSG) of Trypanosoma brucei, which are subject to involved evolutionary pressure. Here, we find striking coevolutionary patterns and distinct information on the molecular evolution of these molecules that question previous work that relied on non-efficient MI
computations.

Zmugg, René; Thaller, Wolfgang; Krispel, Ulrich; Edelsbrunner, Johannes; Havemann, Sven; Fellner, Dieter W.

Procedural Architecture Using Deformation-aware Split Grammars

2014

The Visual Computer, Vol.30 (2014), 9, pp. 1009-1019. Published online: 29 December 2013

With the current state of video games growing in scale, manual content creation may no longer be feasible in the future. Split grammars are a promising technology for large-scale procedural generation of urban structures, which are very common in video games. Buildings with curved parts, however, can currently only be approximated by static pre-modelled assets, and rules apply only to planar surface parts. We present an extension to split grammar systems that allow the creation of curved architecture through integration of free-form deformations at any level in a grammar. Further split rules can then proceed in two different ways. They can either adapt to these deformations so that repetitions can adjust to more or less space, while maintaining length constraints, or they can split the deformed geometry with straight planes to introduce straight structures on deformed geometry.