Mauro Figueiredo

Advanced interaction techniques in virtual environments

Abstract Fundamental to much of the Virtual Reality work is, in addition to high-level 3D graphical and multimedia scenes, research on advanced methods of interaction. The “visitor” of such virtual worlds must be able to act and behave intuitively, as he would in everyday situations, as well as receive expectable natural behaviour presented as feedback from the objects in the environment, in a way that he/she has the feeling of direct interaction with his/her application. In this paper we present several techniques to enrich the naturalness and enhance the user involvement in the virtual environment. We present how the user is enabled to grab objects without using any specific and elaborate hand gesture, which is more intuitive and close to the way humans are used to do. We also introduce a technique that makes it possible for the user to surround objects without any force-feedback interaction device. This technique allows the user to surround or “walk” with the virtual hand on the objects surface and look for the best position to grab it.

An efficient parallel collision detection algorithm for virtual prototype environments

The automatic recognition of geometric constraints in virtual assembly and maintenance operations relies in the determination of intersecting surfaces between virtual prototypes. This is a key challenge in many virtual prototype applications, where it is necessary to find collisions precisely and interactively. This paper presents an algorithm to determine intersecting surfaces at interactive speed in a virtual prototyping environment. The proposed algorithm is based on the overlapping axis-aligned bounding box (OAABB). The OAABB concept is used effectively to eliminate the number of surfaces that cannot intersect and improve performance. The algorithm also facilitates the implementation using parallel computing methods. OpenMP is used, taking advantage of shared memory multiple processors and reducing the overall time complexity of the collision detection algorithm. To achieve an efficient parallel simulation, it is necessary to provide an efficient load balancing scheme. Our experiences in parallelising the code to achieve a better work distribution are also described. Results show that the proposed collision detection achieves interactive rates in real industrial applications as desired.

Augmented Reality and Holograms for the Visualization of Mechanical Engineering Parts

There is an increasing number of students using tablets in schools. Mobile devices gained popularity as an educational tool and there are many schools that use them frequently in educational activities to improve learning. We found that first year students of mechanical engineering in general have difficulties in understanding 3D shapes from 2D views. There are many Augmented Reality (AR) applications available that can be used to create educational contents for these mobile devices. On the other hand, there is an increasing interest in making holograms. In this paper we studied the most popular AR systems and show examples of using an AR system for the visualization of 3D models. We also present the creation of a low cost prototype, the EducHolo, that enables the visualization of holograms supported by tablets. With this prototype students can visualize the hologram of mechanical parts, providing a better perception of the model 3D shape and improving the ability of making the 2D orthographic views and perspectives that they study in the first year of mechanical engineer.

Borrelia hispanica in Ornithodoros erraticus, Portugal

Tick-borne relapsing fever (TBRF) is a spirochetal infection caused by the genus Borrelia. The disease is distributed in the Old and New World with many different species reported. In Europe, TBRF is caused by B. hispanica transmitted to man by Ornithodoros erraticus, a soft tick usually found in old premises to shelter pig herds. In Portugal, the first human case of TBRF was reported in 1942 but since the beginning of the 1960s, the disease has rarely been described and seems to either have disappeared or have been undiagnosed. Therefore, in 2009 a survey was undertaken to evaluate the presence of the tick in this type of premises and to evaluate its role as a reservoir of Borrelia. The work was carried out where the ticks were previously reported in the Alentejo and Algarve regions. Of 63 pigpens surveyed, O. erraticus was collected from 19% (n = 12) of these pigpens using CO(2) traps. To evaluate potential Borrelia hosts, both pigs (n = 25) and small rodents (n = 10) inhabiting these pigpens were surveyed for Borrelia presence, by whole blood PCR and/or tissue culture, respectively. All results for pigs and rodents were negative for the presence of B. hispanica. PCR assays targeting the 16S rRNA gene and intergenic spacer region of Borrelia were used. Sequence analysis of the positive samples confirmed the presence of B. hispanica in 2.2% (n = 5) of ticks from a pigpen in Alentejo. These results confirm natural, but albeit low, persistence of this agent in Portugal.

Cave Chamber Data Modeling and 3D Web Visualization

Underground caves and its specific structures are important for geomorphological studies. In this paper we present tools to identify and map speleothems by surveying cave chambers interiors. The cave chamber was surveyed using Terrestrial Laser Scanning to acquire point clouds with high level of detail for 3D model generation. This data with 45 million points is useful for either reconstruction, geomorphological studies or virtual visits of caves. With this point cloud we generated a 3D-mesh to represent the surface model of the cave chamber, which is important to study its geomorphological features. A topological structure of the 3D-mesh was also implemented to get an efficient algorithm to help identifying stalactites. The possibility to publish 3D data on the Web is of particular interest for the geospatial field. For this reason, it was decided to make the cave model available in the Web by developing a 3D graphical interface where users can navigate and interact with the three-dimensional models of the cave. For this Web3D framework it was used X3D, WebGL and X3DOM. Such solution does not require any additional plug-ins or components.

High-resolution digital 3D models of Algar do Penico Chamber: limitations, challenges, and potential

and/or complex terrains (Pucci & Marambio, 2009; Roncat et al., 2011). Accordingly, with the objective of producing a cave map that identifies the main interior speleothem structures for the purposes of palaeoenvironmental reconstruction, we conducted a terrestrial laser-based survey in a limestone cave. However, rather than just obtaining a map, the present study also aimed to expand 3D-mesh analysis, including the development of two algorithms for determination of stalactite extremities and contour lines, and the interactive visualization of 3D meshes on the Web. The chosen cave is known by local speleologists as Algar do Penico or Algar Guedes (Cavaco, pers. comm.), and is located in the Algarve region in southern Portugal. In this paper, we generate 3D-mesh models of the cave by using surface-reconstruction algorithms. These models can be used to study geomorphological structures and are able to be visualized on graphical interfaces. Several different options are presented for rendering models with high levels of detail from the same point cloud data set. For Web visualization, the selected model is simplified using a decimation method that reduces the download time. We adopt a framework

Web3DGIS for City Models with CityGML and X3D

There is an increasing interest in 3D Geographical Information Systems which leads to the development of web based technologies for visualization, interaction and query of 3D city models. The Open Geographic Consortium developed the City Geography Markup Language as an industry standard for the modeling of city objects. The web 3D Consortium established the eXtendable 3D standard for display of 3D scenes over the internet. This paper presents a Web3DGIS system that loads a cityGML model and convert it to a X3D model. This model can be viewed in the web. Moreover, it also allows the query about attributes and adjacency relationships of features in GIS data sets. For this Web3DGIS it was used X3D, WebGL and X3DOM. Such solution does not require any additional plug-ins or components.

Designing ebook interaction for mobile and contextual learning

Given the global spread of mobile platforms, such as iOS and Android, it is relevant to consider the potential of these devices in teaching and learning. Our exploratory research was designed to evaluate the possibility of using common ebook formats to create gamebooks (gamified books) that are effective in teaching and learning. After analyzing the features available in many free or open tools, we decided to use iBooks Author to built a first model of a dynamic book that may function as an educational game for “Environmental Studies”, aimed at children in the 4th grade, mostly 9-10 years old, in Portuguese schools. This paper presents the design and features of this interactive book titled “Adventures in the Guadiana River”, developed using the Apple iBook format, and especially set for the iPad retina. Because this is a proprietary format we also built a prototype following the EPUB3 standard and developed new ways to interact with content within this universal format. Preliminary tests with our prototypes revealed very good usability and promising pedagogical potential in the proposed models.

Adjustable Approach for Collision Detection in Virtual Prototype Environments

Collision detection is an important task for the simulation of interactions in virtual assembly. This paper presents a novel collision detection algorithm that uses bounding volumes (BV) of different complexity to find intersecting surfaces interactively. This approach uses the surface knowledge available from the CAD model efficiently to build a hierarchical collision detection algorithm. This method also uses different types of bounding volumes with the advantage that is possible to choose the bounding volumes that are more suitable for each type of application. In this way, the user can allow the existence of different types of bounding volumes in simultaneous and he/her can adjust the selection of BVs to the most effective for the determination of intersecting surfaces.

An unified framework to solve the broad and narrow phases of the collision detection problem in virtual prototype environments

The automatic recognition of geometric constraints during user interaction in virtual assembly and maintenance operations relies in the determination of intersecting surfaces between virtual prototypes. This is a central problem in many virtual prototype applications, where it is necessary to find collisions precisely and interactively. This paper presents an unified framework, for the broad and narrow phases of the collision detection problem, to determine precisely intersecting surfaces in a virtual prototyping environment. The proposed algorithm is based on R-tree structures and on the overlapping axis-aligned bounding box (OAABB) for reducing the overall time complexity of the collision detection algorithm. We show that the OAABB concept used together with the R-tree data structure can be used effectively to eliminate the number of surfaces that cannot intersect and improve the performance. The proposed architecture also facilitates the implementation using parallel computing methods.