Integrated Real-Time Calibration of Electromagnetic Tracking of User Motions for Engineering Applications in Virtual Environments

2002 ◽  
Vol 124 (4) ◽  
pp. 623-632 ◽  
Author(s):  
Uma Jayaram ◽  
Roglenda Repp
Keyword(s):  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
Physical World ◽  
Electromagnetic Tracking ◽  
Tracking Systems ◽  
Calibration System ◽  
Time Calibration ◽  
Calibration Accuracy ◽  
Mathematical Techniques

A real-time integrated calibration system for virtual reality environments has been developed that enables accurate electromagnetic tracking of user motions. Electromagnetic tracking systems suffer degradation in accuracy due to the presence of metals and other electromagnetic distortions in the environment. Calibration of the virtual environment to account for these distortions is essential for VR applications in engineering where correlation between the virtual environment and the physical world is important. The major contribution of the paper is the presentation of a comprehensive methodology for calibrating the VR space, the numerical/mathematical techniques proposed for the calibration, and case studies for calibration accuracy and execution time to enable using these techniques in real time in an integrated setup.

Calibrating Virtual Environments for Engineering Applications

2001 ◽  
Author(s):  
Uma Jayaram ◽  
Roglenda Repp
Keyword(s):  
Virtual Environments ◽  
Virtual Environment ◽  
Tracking System ◽  
Physical Space ◽  
Physical World ◽  
Calibration System ◽  
Engineering Applications ◽  
Major Disadvantage ◽  
Cell Densities ◽  
Key Techniques

Abstract A major disadvantage of some tracking systems used in virtual reality environments is the degradation in accuracy due to the presence of metals and other electromagnetic distortions in the environment. Calibration of the virtual environment to account for these distortions is essential for VR applications in engineering where correlation between the virtual environment and the physical world is important. The goal of the calibration process is to map the distorted tracker space to the physical space as accurately as possible for real-time applications. In this paper the authors present an integrated calibration system used with an electromagnetic tracking system. The components of this system are described in detail, including data collection, grid refinement, interpolation, and evaluation. The paper describes different alternatives for measuring systematic errors of magnetic trackers in a room, and for automatically correcting them using various techniques to interpolate between sets of measurements to achieve error estimates and corrections. Several key techniques and algorithms are presented in detail and evaluated in terms of accuracy and execution time over a range of cell densities. Among the interpolation methods considered are inverse distance weighting and affine transformation mappings, as well as variations and combinations of these. The calibration system, called COVE (Calibration of Virtual Environments), has been successful in allowing accurate tracking for several engineering applications.

scholarly journals A New Calibration Process for a Homogeneous Cyclorama Illumination in Virtual TV Sets

2019 ◽  
Vol 9 (10) ◽  
pp. 2020 ◽  
Author(s):  
Roi Méndez ◽  
Enrique Castelló ◽  
José Ramón Ríos Viqueira ◽  
Julián Flores
Keyword(s):  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
Computer System ◽  
Visual Information ◽  
Statistical Study ◽  
Statistical Data ◽  
Calibration Process ◽  
Background Removal ◽  
Custom Software

A virtual TV set combines actors and objects with computer-generated virtual environments in real time. Nowadays, this technology is widely used in television broadcasts and cinema productions. A virtual TV set consists of three main elements: the stage, the computer-system and the chroma-keyer. The stage is composed by a monochrome cyclorama (the background) in front of which actors and objects are located (the foreground). The computer-system generates the virtual elements that will form the virtual environment. The chroma-keyer combines the elements in the foreground with the computer-generated environments by erasing the monochrome background and insetting the synthetic elements using the chroma-keying technique. In order to ease the background removal, the cyclorama illumination must be diffuse and homogeneous, avoiding the hue differences that are introduced by shadows, shines and over-lighted areas. The analysis of this illumination is usually performed manually by an expert using a photometer which makes the process slow, tedious and dependent on the experience of the operator. In this paper, a new calibration process to check and improve the homogeneity of a cyclorama’s illumination by non-experts using a custom software which provides both visual information and statistical data, is presented. This calibration process segments a cyclorama image in regions with similar luminance and calculates the centroid of each of them. The statistical study of the variation in the size of the regions and the position of the centroids are the key tools used to determine the homogeneity of the cyclorama lighting.

Presence in Text-Based Networked Virtual Environments or “MUDS”

1997 ◽  
Vol 6 (5) ◽  
pp. 590-595 ◽  
Author(s):  
John Towell ◽  
Elizabeth Towell
Keyword(s):  
Social Interaction ◽  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
Networked Virtual Environments ◽  
Sense Of Presence ◽  
Networked Virtual Environment ◽  
Being There ◽  
Anecdotal Information

A text-based networked virtual environment represents to a user a system of rooms joined by exits and entrances. When navigating this system of rooms, a user can communicate in real time with other connected users occupying the same room. Hence, these virtual environments are aptly suited for networked conferencing and teaching. Anecdotal information suggested that some people feel a sense of “being there” or presence when connected to one of these environments. To determine how many people feel this sense of presence, we surveyed 207 people from 6 different groups of users of text-based networked virtual environments. The results indicated that 69% of these subjects felt a sense of presence. Experiments with people in text-based networked virtual environments may be helpful in understanding the contribution to presence by social interaction in other virtual environments.

Study on Level-of-Detail for Behavior of Real-Time Virtual Environments

2014 ◽  
Vol 926-930 ◽  
pp. 2118-2121
Author(s):  
Yong Dan Nie ◽  
Yan Zhang ◽  
Xian Mei Liu
Keyword(s):  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
Large Scale ◽  
Level Of Detail ◽  
Virtual Scene ◽  
New Methods ◽  
Level Of Details ◽  
Different Levels

This article based on the level of details (LOD) technology of current geometry layer research, introduced the thinking of technology into the behavior layer of virtual environment characters rendering, as the basis from the important level of the characters and the characters of their location, used different levels of details on the rendering of characters, made a balance between characters rendering time and characters facility and reduced the rendering time of large-scale virtual scene, made an increase the number of virtual scene characters with new methods.

Tracker Modalities for Virtual Environments: A Comparison of Some Performance Characteristics

2002 ◽  
Author(s):  
Roglenda Repp ◽  
Uma Jayaram
Keyword(s):  
Virtual Environments ◽  
Motion Tracking ◽  
Tracking System ◽  
Temporal Stability ◽  
Performance Characteristics ◽  
Electromagnetic Tracking ◽  
Tracking Systems ◽  
Static Distortion ◽  
Electromagnetic Tracking System ◽  
Virtual Reality Application

In this paper the authors present a comparison of some performance characteristics of two motion tracking modalities for use in a virtual environment. Ascension Technology’s Flock of Birds is an electromagnetic tracking system. Intersense’s IS-600 uses a combination of ultrasonic, infrared, and inertial principles. Case studies were performed for both tracking systems to study static distortion, temporal stability, and the effect of metal. The requirements of the virtual reality application would ultimately guide the choice of the tracker modality.

Integrating Sounds and Motions in Virtual Environments

1998 ◽  
Vol 7 (1) ◽  
pp. 67-77 ◽  
Author(s):  
James K. Hahn ◽  
Hesham Fouad ◽  
Larry Gritz ◽  
Jong Won Lee
Keyword(s):  
Genetic Algorithms ◽  
Conceptual Framework ◽  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
Integrated System ◽  
Present System ◽  
Virtual Objects ◽  
Functional Representation

Sounds are often the result of motions of virtual objects in a virtual environment. Therefore, sounds and the motions that caused them should be treated in an integrated way. When sounds and motions do not have the proper correspondence, the resultant confusion can lessen the effects of each. In this paper, we present an integrated system for modeling, synchronizing, and rendering sounds for virtual environments. The key idea of the system is the use of a functional representation of sounds, called timbre trees. This representation is used to model sounds that are parameterizable. These parameters can then be mapped to the parameters associated with the motions of objects in the environment. This mapping allows the correspondence of motions and sounds in the environment. Representing arbitrary sounds using timbre trees is a difficult process that we do not address in this paper. We describe approaches for creating some timbre trees including the use of genetic algorithms. Rendering the sounds in an aural environment is achieved by attaching special environmental nodes that represent the attenuation and delay as well as the listener effects to the timbre trees. These trees are then evaluated to generate the sounds. The system that we describe runs parallel in real time on an eight-processor SGI Onyx. We see the main contribution of the present system as a conceptual framework on which to consider the sound and motion in an integrated virtual environment.

scholarly journals A virtual platform for real-time performance analysis of electromagnetic tracking systems for surgical navigation

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 103
Author(s):  
Mattia Alessandro Ragolia ◽  
Filippo Attivissimo ◽  
Attilio Di Nisio ◽  
Anna Maria Lucia Lanzolla ◽  
Marco Scarpetta
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Surgical Navigation ◽  
Surgical Instruments ◽  
Accurate Estimation ◽  
Electromagnetic Tracking ◽  
Tracking Systems ◽  
Virtual Platform ◽  
Magnetic Field Generator ◽  
The Magnetic Field

<p class="Abstract">Electromagnetic Tracking Systems (EMTSs) are widely used in surgical navigation, allowing to improve the outcome of diagnosis and surgical interventions, by providing the surgeon with real-time position of surgical instruments during medical procedures. However, particular effort was dedicated to the development of efficient and robust algorithms, to obtain an accurate estimation of the instrument position for distances from the magnetic field generator beyond 0.5 m. Indeed, the main goal is to improve the limited range of current commercial systems, which strongly affects the freedom of movement of the medical team. Studies are currently being conducted to optimize the magnetic field generator configuration (both geometrical arrangements and electrical properties) since it affects tracking accuracy. In this paper, we propose a virtual platform for assessing the performance of EMTSs for surgical navigation, providing real-time results and statistics, and allowing to track instruments both in real and simulated environments. Simulations and experimental tests are performed to validate the proposed virtual platform, by employing it to assess the performance of a real EMTS. The platform offers a real-time tool to analyze EMTS components and field generator configurations, for a deeper understanding of EMTS technology, thus supporting engineers during system design and characterization.</p>

scholarly journals Comparing and Evaluating Real Time Character Engines for Virtual Environments

2010 ◽  
Vol 19 (2) ◽  
pp. 95-117 ◽  
Author(s):  
Marco Gillies ◽  
Bernhard Spanlang
Keyword(s):  
Open Source ◽  
Virtual Environments ◽  
Real Time ◽  
Virtual Environment ◽  
State Of The Art ◽  
The State ◽  
Animated Characters

As animated characters increasingly become vital parts of virtual environments, then the engines that drive these characters increasingly become vital parts of virtual environment software. This paper gives an overview of the state of the art in character engines, and proposes a taxonomy of the features that are commonly found in them. This taxonomy can be used as a tool for comparison and evaluation of different engines. In order to demonstrate this we use it to compare three engines. The first is Cal3D, the most commonly used open source engine. We also introduce two engines created by the authors, Piavca and HALCA. The paper ends with a brief discussion of some other popular engines.

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