Marcelo Knörich Zuffo

On the usability of gesture interfaces in virtual reality environments

This paper discusses several usability issues related to the use of gestures as an input mode in multimodal interfaces. The use of gestures has been suggested before as a natural solution for applications that require hands-free and notouch interaction with computers, such as in virtual reality (VR) environments. We introduce a simple but robust 2D computer vision based gesture recognition system that was successfully used for interaction in VR environments such as CAVEs and Powerwalls. This interface was tested under 3 different scenarios, as a regular pointing device in a GUI interface, as a navigation tool, and as a visualization tool. Our experiments show that the time to completion of simple pointing tasks is considerably slower when compared to a mouse and that its use during even short periods of time causes fatigue. Despite, these drawbacks, the use of gestures as an alternative mode in multimodal interfaces offers several advantages, such as quick access to computing resources that might be embedded in the environment, using a natural and intuitive way, and that scales nicely to group and collaborative applications, where gestures can be used sporadically.

JINX: an X3D browser for VR immersive simulation based on clusters of commodity computers

In this paper we present JINX, a fully distributed virtual environments browser, which has a special support for commodity computer clusters and immersive visualization devices. The presented mechanism intends to be fast and easy to use to develop virtual reality applications based on the X3D format, enabling great flexibility for displays and interaction devices, allowing users to concentrate only on content creation. JINX provides support for nodes synchronization and resources sharing, from Framelock to Datalock. This paper describes the background of the decisions made and the problems that had to be overcome.

An experience using X3D for virtual cultural heritage

In this paper we present our experience in using Virtual Reality Technologies to accurately reconstruct and further explore ancient and historic city buildings. Virtual reality techniques provide a powerful set of tools to explore and access the history of a city. In order to explore, visualize and hear such history, we divided the process in three phases: historical data gathering and analysis; 3D reconstruction and modeling; interactive immersive visualization, auralization and display. The set of guidelines devised helped to put into practice the extensible tools available in VR but not always easy to put together by inexperienced users. These guidelines also helped the smoothness of our work and helped avoiding problems in the subsequent phases. Most importantly, the X3D standard provided an environment capable of helping the design and validation process as well as the visualization phase. To finalize, we present the results achieved and further analyze the extensibility of the framework. Although VR tools and techniques are widely available at present, there is still a gap between using the tools and really taking advantage of VR in historic architectural reconstruction so that users might immerse themselves into this world and thus be able to consider various scenarios and possibilities that might lead to new insightful inspiration. This is an ongoing process that we think will increase and help current architectural development.

Accessible display design to control home area networks

Recently, the social inclusion and technical aid to assure autonomy to people with disabilities are getting attention all over the world. We present a display design for accessible interaction in home area networks. Based on a research on the accessible interfaces state of the art, an interface design was proposed. This interface was implemented over a Tablet that controls the domestic devices through a home network controller prototype. In order to evaluate the design, a research was conducted, interviewing people with disabilities in Brazil. This research consolidated a feasible accessible interface to control home area networks pointing out the main requirements for home area networks considering a diversified group of impairments.

Three-dimensional segmentation of the tumor in computed tomographic images of neuroblastoma.

Segmentation of the tumor in neuroblastoma is complicated by the fact that the mass is almost always heterogeneous in nature; furthermore, viable tumor, necrosis, and normal tissue are often intermixed. Tumor definition and diagnosis require the analysis of the spatial distribution and Hounsfield unit (HU) values of voxels in computed tomography (CT) images, coupled with a knowledge of normal anatomy. Segmentation and analysis of the tissue composition of the tumor can assist in quantitative assessment of the response to therapy and in the planning of delayed surgery for resection of the tumor. We propose methods to achieve 3-dimensional segmentation of the neuroblastic tumor. In our scheme, some of the normal structures expected in abdominal CT images are delineated and removed from further consideration; the remaining parts of the image volume are then examined for the tumor mass. Mathematical morphology, fuzzy connectivity, and other image processing tools are deployed for this purpose. Expert knowledge provided by a radiologist in the form of the expected structures and their shapes, HU values, and radiological characteristics are incorporated into the segmentation algorithm. In this preliminary study, the methods were tested with 10 CT exams of four cases from the Alberta Childrens Hospital. False-negative error rates of less than 12% were obtained in eight of the 10 exams; however, seven of the exams had false-positive error rates of more than 20% with respect to manual segmentation of the tumor by a radiologist.

The Brazilian digital television system access device architecture

In early 2003, the Brazilian government accelerated the decision process on analog to digital transition of terrestrial TV broadcast infrastructure, naming this initiative The Brazilian Digital Television System (SBTVD). This paper describes the access device architecture we have proposed for the SBTVD, as well as related issues. We focused on several requirements among which: flexibility to support the social economical diversity enabling market implementations that can vary on cost, complexity and applications; digital inclusion targeting a minimal cost architecture providing a simple access device to information and services by convergent broadcast and point-to-point telecommunication means; and scalability targets incorporating state-of-the-art technology, considering emerging services and the current legacy analog TV infrastructure available in Brazil. We cover the following specific topics: an architecture overview considering scalability, interoperability and regional and international requirements, operating system and middleware interfaces, audio and video coding formats and associate standards, technical and economical analysis, usability and user interface consistency. Finally two prototypes for the outlined access device architecture are reported.

Estimation of the tissue composition of the tumour mass in neuroblastoma using segmented CT images

Neuroblastoma is the most common extra-cranial, solid, malignant tumour in children. Advances in radiology have made possible the detection and staging of the disease. Nevertheless, there is no method available at present that can go beyond detection and qualitative analysis, towards quantitative assessment of the tissues composition of the primary tumour mass in neuroblastoma. Such quantitative analysis could provide important information and serve as a decision-support tool to the radiologist and the oncologist, result in better treatment and follow-up and even lead to the avoidance of delayed surgery. The problem investigated was the improvement of the analysis of the primary tumour mass, in patients with neuroblastoma, using X-ray computed tomography (CT) images. A methodology was proposed for the estimation of the tissue content of the mass: it comprised a Gaussian mixture model for estimation, from segmented CT images, of the tissue composition of the primary tumour. To demonstrate the potential of the method, the results are presented of its application to ten CT examinations of four patients. The method provides quantitative information, and it was observed that the tumour in one of the patients reduced from 523 cm3 to 81 cm3 in volume, with an increase in calcification from about 20% to about 88% of the tumour volume, in response to chemotherapy over a period of five months. Results indicate that the proposed technique may be of considerable value in assessing the response to therapy of patients with neuroblastoma.

Graphical interaction devices for distributed virtual reality systems

This paper explores the possibilities of using portable devices in multiprojection environments, such as CAVEs, Panoramas and Power Walls. We propose and implement a tool to generate graphical interfaces in a straightforward manner. These interfaces are light and can be run on PDAs. The interface application communicates transparently with a graphic cluster, via any underlying network system, which processes the events and maintains the synchrony of the rendered images in real-time. This tool is part of Glass, a library for distributed computing. We present two examples of applications: Cathedral and Celestia.

Spheree: a 3D perspective-corrected interactive spherical scalable display

We constructed a personal, spherical, multi-projector perspective-corrected rear-projected display called Spheree. Spheree uses multiple calibrated pico-projectors inside a spherical display with content rendered from a user-centric viewpoint. Spheree uses optical tracking for head-coupled rendering, providing parallax-based 3D depth cues. Spheree is compact, supporting direct interaction techniques. For example, 3D models can be modified via 3D interactions on the sphere, providing a 3D sculpture experience.

Over the air download for digital television receivers upgrade

Over the air download is an important feature for terrestrial digital television systems. It provides a cheaper option for DTV receiver manufacturers to provide bug fixes and quality improvements to their products, allowing a shorter time to the market. This paper presents a mechanism proposal of an over the air download software update for the Brazilian system. This mechanism was specified considering the Brazilian DTV over the air download specifications, but it was extended considering efficiency, reliability and user transparency as requirements for software update. A proof of concept was implemented on a Linux based set-top box. The mechanism is divided into five main functional parts: download schedule, packets download, packets authentication, installation and error robustness. Some analyses were conducted upon the implementation considering the following criteria: download robustness and maximum downloading rate.