Jauvane C. de Oliveira

VELVET: an adaptive hybrid architecture for very large virtual environments

Collaborative virtual environment (CVE) concepts have been used in many systems in the past few years. Applications of such technology range from military combat simulations to various civilian commercial applications. The architectures available today provide support for a number of users, but they fail if too many users are together in a small space in the virtual world. This paper introduces VELVET, an adaptive hybrid architecture that allows a greater number of users to interact through a CVE. This is accomplished through an adaptive filtering scheme based on multicasting. VELVET also supports small groups of users, but its use in large environments shows the greatest potential, better handling local concentrations of activity than region-, cell-, orlocale-based approaches. VELVET introduces a novel adaptive area of interest management that supports heterogeneity amongst the various participants. This allows users in a supercomputer with high-speed networking to successfully collaborate with others in not-so-powerful systems behind a slow dial-up connection.

A hybrid P2P communications architecture for zonal MMOGs

Distributed Virtual Environments are becoming more popular in today’s computing and communications among people. Perhaps the most widely used form of such environments is Massively Multiplayer Online Games (MMOG), which are in the form of client/server architecture that requires considerable server resources to manage a large number of distributed players. Peer-to-peer communication can achieve scalability at lower cost but may introduce other difficulties. Synchronous communication is a prime concern for multi-user collaborative applications like MMOGs where players need frequently interaction with each other to share their game states. In this article, we present a hybrid MMOG architecture called MM-VISA (Massively Multiuser VIrtual Simulation Architecture). In this architecture, servers and peers are coupled together to take the inherent advantages of the centralized architecture and the scalability of distributed systems. As the virtual world is decomposed into smaller manageable zones, the players’ random movement causes reorganization at the P2P overlay structure. The frequent nature of movements along with unintelligent zone crossing approaches, currently implemented in MMOGs, breaks synchronous communication. To limit such problem, we consider players’ gaming characteristics to intelligently define routing paths. A graph-theoretic framework is incorporated for overlay oriented real-time distributed virtual environments. We shall show that interest-driven zone crossing, dynamic shared region between adjacent zones, and clustering of entities based on their attributes significantly decrease unstable overlay situations. The effectiveness of the presented system is justified through simulation.

A Visibility-Driven Approach for Zone Management in Simulations

Massively multi-user simulations aim to support a large number of users while keeping the communication among the parties synchronous and highly interactive. In this paper, we present a collaborative virtual architecture that supports a large number of users by dividing the virtual environment into multiple adjacent hexagonal regions in order to manage the interest of the entities. A master node, called a hybrid node, constructs a Peer-to-Peer (P2P) overlay network to connect and manage nodes that lie in its region. Messaging is done at the application layer rather than the network layer, and a node-joining algorithm is proposed to reflect the underlying network physical topology onto the data distribution pathways among the end hosts to enhance the system performance. In addition, the introduction of a buffer zone between adjacent zones reduces the number of connections and disconnections that occur when a node frequently moves at the boundary of the two zones and provides more resilience to the system. We also attempt to shift the messaging among parties in one region from a zone-based method to a visibility-driven method to refine their interest by enabling message filtering. The effectiveness of this collaboration architecture is tested through a prototype implementation and a high level application.

A Novel Method for Supporting Massively Multi-user Virtual Environments

In collaborative distributed virtual environment people interact with each other to shard their states. In this paper we present massively multi-user virtual simulation architecture - MMVISA. The framework partitions the simulation platform into multiple regions to properly organize the decorative entities and to efficiently manage their association. The coordinator, the leader of a zone, manages local communications in multicast fashion but this multicast functionality is shifted from the network layer to the application layer to get the benefit of the scalability and easy deployability. Considering the behavior of the entities, coordinator opens multiple multicast channels to reduce structural reformation events among the entities. On the other hand, coordinators themselves form a top level mesh hierarchy to manage the area of interest. A mathematical model is given to determine the best node in the best zone with a given interest vector. This gives a provision to a node to import all the interesting messages when needed and makes it easy to be virtually there

Hand gesture recognition from depth and infrared Kinect data for CAVE applications interaction

This paper presents a real-time framework that combines depth data and infrared laser speckle pattern (ILSP) images, captured from a Kinect device, for static hand gesture recognition to interact with CAVE applications. At the startup of the system, background removal and hand position detection are performed using only the depth map. After that, tracking is started using the hand positions of the previous frames in order to seek for the hand centroid of the current one. The obtained point is used as a seed for a region growing algorithm to perform hand segmentation in the depth map. The result is a mask that will be used for hand segmentation in the ILSP frame sequence. Next, we apply motion restrictions for gesture spotting in order to mark each image as a ‘Gesture’ or ‘Non-Gesture’. The ILSP counterparts of the frames labeled as “Gesture” are enhanced by using mask subtraction, contrast stretching, median filter, and histogram equalization. The result is used as the input for the feature extraction using a scale invariant feature transform algorithm (SIFT), bag-of-visual-words construction and classification through a multi-class support vector machine (SVM) classifier. Finally, we build a grammar based on the hand gesture classes to convert the classification results in control commands for the CAVE application. The performed tests and comparisons show that the implemented plugin is an efficient solution. We achieve state-of-the-art recognition accuracy as well as efficient object manipulation in a virtual scene visualized in the CAVE.

Simulator for minimally invasive vascular interventions: Hardware and software

In the present work, a simulation system is proposed that can be used as an educational tool by physicians in training basic skills of minimally invasive vascular interventions. In order to accomplish this objective, initially the physical model of the wire proposed by Konings has been improved. As a result, a simpler and more stable method was obtained to calculate the equilibrium configuration of the wire. In addition, a geometrical method is developed to perform relaxations. It is particularly useful when the wire is hindered in the physical method because of the boundary conditions. Then a recipe is given to merge the physical and the geometrical methods, resulting in efficient relaxations. Moreover, tests have shown that the shape of the virtual wire agrees with the experiment. The proposed algorithm allows real-time executions, and furthermore, the hardware to assemble the simulator has a low cost.

Right Hand Rehabilitation with CyberForce, CyberGrasp, and CyberGlove

VR-based rehabilitation aims at allowing more engaging physiotherapy sessions. This work introduces a VR system for right hand rehabilitation which uses a CyberForce/CyberGrasp/CyberGlove system.

An instrument for measuring force vector and frequency of CPR compressions

Cardio-Pulmonary Resuscitation (CPR) is a technique that allows a CPR certified person to keep alive someone whose heartbeat and/or breathing has stopped. Through compressions applied to the thorax of the individual in need of help, one can maintain the blood flow and air intake until further help (and equipment) arrives. Training for CPR is performed using manikins that mimic a human torso. In this paper, we design an instrument for measuring the force vector (magnitude and direction) and frequency of CPR compressions applied during CPR training sessions, to help a trainer objectively evaluate the performance of trainees. Excessive/insufficient force or frequency of compressions will harm, not help, the person in need. So it is important for a trainer to measure these parameters. Our instrument uses the standard CPR manikin plus a Nintendo Wii Fit balance board, and is therefore practical and affordable. Our experiments conducted with real subjects show that our system can measure these parameters with a standard uncertainty of 1.96 N, 0.79 degrees, and 0.26 Hz, respectively for force, direction and frequency.

A Haptic Rehabilitation System

Virtual Reality has been used by rehabilitation professionals as a way to keep patients motivated while performing neuroplasticity functional exercises. This work describes a virtual environment which uses the CyberForce/CyberGrasp/CyberGlove system to enable a functional rehabilitation setup. The user of the system is supposed to be individuals who have been affected by traumatology, degenerative or neurological injuries, through the simulation of everyday life procedures.

Virtual Walking in a Synthetic World through an Low-Cost Interaction Device

Those who work in risky areas need to have proper training which may allow them to know how to behave in case of need. The training needs to mimic risk scenarios, where the individuals may exercise proper procedures. It is also necessary that such individuals get to know the surrounding of their specific work place, so that they can be able to use proper escape routes, even under stress. Virtual Reality, and the related Virtual Environments, have been shown to be quite effective in training applications. Good examples range from Flight Simulators to more recent efforts in various training scenarios. This work introduces a low-cost offshore oil platform training simulation, which allows a user to exploit the synthetic environment through free walking in the environment. The system uses a Nintendo Wii Fit Plus Balance Board to allow a user to walk in the system using natural leg movements. The 3D models of the offshore oil platform are presented in a low-cost CAVE setup in a Collaborative Virtual Environments, which includes avatars that represent other users of the system, both bots and those representing other real users.