Jiri Zara

Fast depth of field rendering with surface splatting

We present a new fast algorithm for rendering the depth-of-field effect for point-based surfaces. The algorithm handles partial occlusion correctly, it does not suffer from intensity leakage and it renders depth-of-field in presence of transparent surfaces. The algorithm is new in that it exploits the level-of-detail to select the surface detail according to the amount of depth-blur applied. This makes the speed of the algorithm practically independent of the amount of depth-blur. The proposed algorithm is an extension of the elliptical weighted average (EWA) surface splatting. We present a mathematical analysis that extends the screen space EWA surface splatting to handle depth-of-field rendering with level-of-detail, and we demonstrate the algorithm on example renderings.

Sketching Cartoons by Example

We introduce a novel example-based framework for reusing traditional cartoon drawings and animations. In contrast to previous approaches our aim is to design new characters and poses by combining fragments of the original artwork. Using standard image manipulation tool this task is tedious and time consuming. To reduce the amount of manual intervention we combine unsupervised image segmentation, fragment extraction and highquality vectorization. The user can simply select an interesting part in the original image and then adjust it in a new composition using a few control scribbles. Thanks to ease of manipulation proposed sketch-based interface is suitable both for experienced artists and unskilled users (e.g. children) who wish to create new stories in the style of masters. Practical results confirm that using our framework high-quality cartoon drawings can be produced within much shorter time frames as compared with standard approaches.

Graph Cut Based Point-Cloud Segmentation for Polygonal Reconstruction

The reconstruction of 3D objects from a point-cloud is based on sufficient separation of the points representing objects of interest from the points of other, unwanted objects. This operation called segmentation is discussed in this paper. We present an interactive unstructured point-cloud segmentation based on graph cut method where the cost function is derived from euclidean distance of point-cloud points. The graph topology and direct 3D point-cloud segmentation are the novel parts of our work. The segmentation is presented on real application, the terrain reconstruction of a complex miniature paper model, the Langweil model of Prague.

A scalable approach to visualization of large virtual cities

Visualization of large urban complexes on the Web is a highly demanding task both from the networking and computational point of view. The whole three-dimensional model of a city is mostly too big to be downloaded in a reasonable time and to be stored in a memory of commonly used computers. This paper presents a scalable approach for subdividing an urban model into smaller parts. Dynamic loading and unloading data allows theoretically unlimited extension of a model with constant network and computation load. Further requirements specific to presentation of virtual cities are also discussed. Theoretical considerations are followed by a practical implementation utilizing the VRML language for modeling the historical city of Prague.

Cultural heritage presentation in virtual environment: Czech experience

The permanently increasing graphical power of commonly used computers opens the possibility to present highly detailed and richly textured three-dimensional models of cultural complexes using the Web. Utilizing virtual reality paradigms, both experts and ordinary users can explore pieces of cultural heritage in a virtual environment. This paper introduces three different approaches to cultural heritage modeling and presentation in the Czech Republic. The first example, Celtic oppidum Zavist, represents a simple but efficient utilization of virtual reality for archaeology. The next project, Virtual Old Prague, is a complex Web-based application allowing dynamic walks through virtual cities. Such models can be theoretically of any size. Finally, the on-going EU project, Virtual Heart of Central Europe, is an example of several cultural heritage sites thematically interconnected into a common virtual environment.

Virtual Reality Course - A Natural Enrichment of Computer Graphics Classes

This paper shows how the Virtual Reality (VR) course can naturally extend and practice a wide range of Computer Graphics (CG) principles and programming techniques. Thanks to real‐time processing requirements, attention is paid to efficient modeling conventions, time‐saving rendering approaches, and user interfaces allowing a smooth navigation in a virtual environment. All these issues play an important role especially when designing virtual worlds targeted to the web, i.e. utilizing VRML/X3D standards. The paper presents a structure and related information of the VR course that has been taught at various universities during the last 6 years. Our experience clearly demonstrates that students appreciate its contents even if they already completed courses on 3D graphics.

Virtual House of European Culture: e-AGORA

This co-operative project links up important European centres of art and culture and creates an open network with an innovative application of the new information technologies: the creation of an unconventional and highly efficient communication base founded on an interactive, multimedia and transdisciplinary approach to the production and presentation of contemporary forms of performing arts. The main channel of this project is the revolutionary communication and navigation system e-AGORA, which enables visitors to move intuitively in a virtual 3D environment on the Internet. In the VIRTUAL HOUSE OF EUROPEAN CULTURE a broad spectrum of the public can investigate contemporary Euro-regional artistic programs in real time and communicate interactively. At the same time, it is an instrument of individual and collective artwork in the domain of contemporary performing arts as it opens up a new horizon for a multidisciplinary form of artistic expression and presentation of artworks. The implementation of the project VIRTUAL HOUSE OF EUROPEAN CULTURE also has important theoretical and educational dimensions: a series of practical workshops, an international academic conference, thematic exhibitions, the production of the e-AGORA CD-ROM and a printed publication.

3D Talking-Head Interface to Voice-Interactive Services on Mobile Phones

This paper presents a novel framework for easy creation of interactive, platform-independent voice-services with an animated 3D talking-head interface, on mobile phones. The Framework supports automated multi-modal interaction using speech and 3D graphics. The difficulty of synchronizing the audio stream to the animation is examined and alternatives for distributed network control of the animation and application logic is discussed. The ability of modern mobile devices to handle such applications is documented and it is shown that the power consumption trade-off of rendering on the mobile phone versus streaming from the server favors the phone. The presented tools will empower developers and researchers in future research and usability studies in the area of mobile talking-head applications Figure 1. These may be used for example in entertainment, commerce, health care or education.

Cultural Heritage, User Interfaces and Serious Games at CTU Prague

Cultural heritage presentation is a topic we at CTU Prague deal with for more than ten years. In this paper we present our experience with user interface design where serious games paradigm has been utilized. The survey of selected projects represents various technologies and approaches for cultural heritage data handling that includes data acquisition, presentation, interaction and educational issues. The aim of our activities was to develop a systematic approach to the user interface design for the given class of applications.

Concise Tour to the Virtual Old Prague

This paper describes a structure and a user interface of the Internet based 3D presentation of existing historical part of city Prague. The application offers a smooth tour to selected regions of the real city, utilizing number of standard and modern technologies including VRML, Java, and PHP. The architecture of the whole virtual model is presented together with several advanced and specific features like dynamic loading und unloading objects or newly proposed LOD for urban scenes. This running web application seems to be currently unique in terms of complexity, functionality, and scaleability for further growth. The paper introduces methodology suitable for immediate creation of arbitrary virtual city according to a real one.