Virtual Sky Research Articles

Distance estimation technique from 360-degree images in built-in environments

The present study introduces a novel approach for quantifying distances within constructed environments. A mathematical model was developed for distance estimation in image processing using width and height estimation. In order to determine distance, the study employed the use of visual angle and sky view factor (SVF). Additionally, a camera with capabilities similar to the human eye was utilized to capture 360-degree photographs from a fixed position within a virtual reality corridor. The technique of Sky View Factor (SVF) is employed in indoor environments with ceilings by eliminating windows, doors, and roofs, thereby simulating a virtual sky. This enables the calculation of various parameters such as the image's area, area fraction, and aspect ratio through the utilization of image processing methods. Distance estimation can be predicted through the utilization of the sky view factor and visual angle, employing a linear regression analysis. The method of virtual sky view factor (VSVF) has potential applications in the fields of Engineering, robotics, and architecture for the estimation of indoor distances.

Effects of nature-adapted lighting solutions ("Virtual Sky") on subjective and objective correlates of sleepiness, well-being, visual and cognitive performance at the workplace.

Exposure to natural daylight benefits human well-being, alertness, circadian rhythms and sleep. Many workplaces have limited or no access to daylight. Thus, we implemented a light-panel ("Virtual Sky"), which reproduced nature-adapted light scenarios. In a laboratory office environment, three lighting scenarios were presented during the day: two lighting conditions with nature-adapted spectral light distributions, one with static and one with dynamic clouds, and a standard office lighting condition. We compared the impact of the three lighting scenarios on subjective and objective measures of alertness, cognitive performance, wellbeing, visual comfort, contrast sensitivity, and cortisol levels in 18 healthy young male volunteers in a within-participant cross-over study design. We found no evidence that an 8-h lighting scenario with static or dynamic clouds during the waking day (9am-5pm) was associated with any significant effect on objective and/or subjective alertness, cognitive performance and morning cortisol concentrations compared to standard workplace lighting. However, the dynamic light scenario was accompanied with lower levels of perceived tensionafter completing cognitive tasks and less effort to concentrate compared to the static lighting scenarios. Our findings suggest that apart from smaller effects on tension and concentration effort, nature-adapted lighting conditions did not improve daytime alertness and cognitive performance in healthy well-rested young participants, as compared to standard office lighting.

WITHDRAWN: Missile Trajectory Defense Planning based on Distributed Neural Network

In this article, the development status, models and learning algorithms of distributed neural networks are investigated, conventional BP algorithms are analyzed, some improved algorithms are proposed, and the principle and structure of neural network PID controllers are discussed. In addition, a distributed neural network is used to predict the trajectory of the missile and develop an appropriate attack prevention plan. At the same time, the construction of the virtual world will be introduced by constructing the virtual sky and terrain in the simulation process, changing the perspective in the virtual world, and completing the ballistic counterattack plan of the missile. The purpose of the anti-attack plan is to provide technical reserves for the further development of the National Missile Defense Program, so that the Ministry of Defense can update the technology demonstration system of the existing bases, reduce risks and accelerate technological updates. In order to solve the problem of peculiar or drastic changes in the existing trajectory tracking deviation, we introduced a new method that takes the trajectory arc as the independent variable, and built a linear variable parameter system for trajectory tracking on this basis, and calculated a new automatic Tracking deviation under variable.

Teaching planetary retrograde motion using a local positioning system

For millennia, humans have observed planetary retrograde motion and attempted to explain the phenomena. Our modern understanding of the motions of bodies within the Solar System is built up from a rich history of past models, each of which tried to explain astronomical observations while also being influenced by the contemporary belief system. One of the pivotal observations that assisted astronomers in the development of our current planetary model is planetary retrograde motion. Complexities in heliocentric and geocentric planetary models coupled with the change of reference frame required to visualize retrograde can be challenging for students. For this reason, we developed a kinaesthetic learning activity for introductory physics and astronomy courses that requires students to physically walk planetary orbits and allows them to see apparent motions across a virtual sky in real-time. In this paper, we present multiple activities using a local positioning system that are based on changing historical models for the retrograde phenomenon. We aim for these activities to culminate in students’ holistic understanding of how astronomically observed retrograde patterns were explained by models stemming from the existing scientific knowledge and beliefs available at the time.

Virtual Sky View Factor (Vsvf) and Field of View (Fov) as New Dimensional Perception Components

Virtual Sky View Factor (Vsvf) and Field of View (Fov) as New Dimensional Perception Components

Matched-filter coding of sky polarization results in an internal sun compass in the brain of the desert locust

Many animals use celestial cues for spatial orientation. These include the sun and, in insects, the polarization pattern of the sky, which depends on the position of the sun. The central complex in the insect brain plays a key role in spatial orientation. In desert locusts, the angle of polarized light in the zenith above the animal and the direction of a simulated sun are represented in a compass-like fashion in the central complex, but how both compasses fit together for a unified representation of external space remained unclear. To address this question, we analyzed the sensitivity of intracellularly recorded central-complex neurons to the angle of polarized light presented from up to 33 positions in the animal's dorsal visual field and injected Neurobiotin tracer for cell identification. Neurons were polarization sensitive in large parts of the virtual sky that in some cells extended to the horizon in all directions. Neurons, moreover, were tuned to spatial patterns of polarization angles that matched the sky polarization pattern of particular sun positions. The horizontal components of these calculated solar positions were topographically encoded in the protocerebral bridge of the central complex covering 360° of space. This whole-sky polarization compass does not support the earlier reported polarization compass based on stimulation from a small spot above the animal but coincides well with the previously demonstrated direct sun compass based on unpolarized light stimulation. Therefore, direct sunlight and whole-sky polarization complement each other for robust head direction coding in the locust central complex.

Universal Visible Sky Factor: A method for calculating the three-dimensional visible sky ratio

This paper developed a new methodology for evaluating the visible sky ratio of a vertical building surface. A visible sky ratio is based on a surface viewpoint and measured by projecting obstacles onto a virtual three-dimensional (3D) hemisphere. Typically, virtual sky projection methods use two-dimensional (2D) mapping to calculate the amount of view of the outside. A major concern with 2D mapping is loss of accuracy due to the distortions in geometry that occur during the projection process. To address this limitation, a new projection method has been developed, supported by a computational numeric model that calculates the actual projection area of obstacles onto a 3D hemisphere. The new method improves the accuracy of the visible sky ratio without distorting obstructions. This new method can handle more complex conditions such as the forms of surrounding buildings, as well as various layouts, orientations, and heights. This study examines the new method via existing calculation processes in order to determine its robustness and limitations. The proposed method compared positively to these other existing methods, especially in terms of vertical changes in the observation point.

Development of a Motion Sensing and Automatic Positioning Universal Planisphere Using Augmented Reality Technology

This study combines the augmented reality technology and the sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices to develop a motion sensing and automatic positioning universal planisphere. It can create local star charts according to the current date, time, and position and help users locate constellations on the planisphere easily through motion sensing operation. By holding the mobile device towards the target constellation in the sky, the azimuth and elevation angles are obtained automatically for mapping to its correct position on the star chart. The proposed system combines observational activities with physical operation and spatial cognition for developing correct astronomical concepts, thus making learning more effective. It contains a built-in 3D virtual starry sky to enable observation in classroom for supporting teaching applications. The learning process can be shortened by setting varying observation date, time, and latitude. Therefore, it is a useful tool for astronomy education.

Physically Plausible Methods for Projecting Changes in Great Lakes Water Levels under Climate Change Scenarios

Abstract A method for projecting the water levels of the Laurentian Great Lakes under scenarios of human-caused climate change, used almost to the exclusion of other methods in the past, relies very heavily on the large basin runoff model (LBRM) as a component for determining the water budget for the lake system. This model uses near-surface air temperature as a primary predictor of evapotranspiration (ET); as in previous published work, it is shown here that the model’s very high sensitivity to temperature causes it to overestimate ET in a way that is greatly at variance with the fundamental principle of conservation of energy at the land surface. The traditional formulation is characterized here as being equivalent to having several suns in the virtual sky created by LBRM. More physically based methods show, relative to the traditional method, often astoundingly less potential ET and less ET, more runoff from the land and net basin supply for the lake basins, and higher lake water levels in the future. Using various methods of estimating the statistical significance, it is found that, at minimum, these discrepancies in results are significant at the 99.998% level. The lesson for the larger climate impact community is to use caution about whether an impact is forced directly by air temperature itself or is significantly forced by season or latitude independently of temperature. The results here apply only to the water levels of the Great Lakes and the hydrology of its basin and do not affect larger questions of climate change.

The freedom to teach: Using open educational resources in your courses

Open educational resources (OER) are “high-quality, openly licensed, online educational materials that offer an extraordinary opportunity for people everywhere to share, use, and reuse knowledge” (William and Flora Hewlett Foundation, n.d.). These materials range from full courses and course materials (including textbooks) to streaming videos and software.Innovative educators recognize that OER offer an exciting alternative to restrictive (and expensive) textbooks by allowing them the freedom to select quality content that better fits their pedagogy. Students benefit from more engaged learning, lower costs, and the ability to revise and remix these materials as assigned by their instructor. The virtual sky is the limit!The 4-VA Collaborative at George Mason University recently announced a competitive grants pilot program (February, 2016) to incentivize Mason instructional faculty to identify existing, or create new, open digital content and incorporate it into their course(s). The proposed interactive presentation session will build on the Mason 4-VA pilot program. A team of four faculty members from Mason and J. Sargeant Reynolds Community College will lead the session. Discussion topics to be covered include defining OER, describing Creative Commons licenses, strategies for integrating OER in courses, and identifying quality materials. Participants should bring a laptop as they will be divided into small groups during the session to familiarize themselves with websites that aggregate OER content applicable to their discipline(s).By the end of this session, participants will be able to:Define OER,Understand Creative Commons licenses,Outline the first steps in planning an OER project, andIdentify some online sources for discipline-specific OER.We anticipate that OER collaborations will emerge from this session. ReferencesMason 4-VA Collaborative. (February, 2016). Course Redesign: Using Open Educational Resources. Retrieved from http://4va.gmu.edu/call-for-proposals William and Flora Hewlett Foundation. (n.d.) Open Educational Resources. Retrieved from http://www.hewlett.org/programs/education/open-educational-resources

Covering photo-realistic properties of outdoor components with the effects of sky color in mixed reality

Outdoor rendering is an attractive topic in computer graphics. In this paper our main concern is to reveal the interaction between sky color and virtual objects in Mixed Reality environments. Although registration and tracking are two of the main issues in building effective Augmented Reality (AR) systems the creation of more realistic virtual objects indistinguishable from their real-world counterparts is our target which is currently the ultimate goal in AR. Two classes of sky color generation are employed to reveal the outdoor-element interaction. Virtual Sky Modelling (VSM) based on the Perez Model is capable of generating the sky color in a specific location, date and time. The second technique is to generate a virtual model based on the real image of the sky which is called in this paper Real Sky Modelling (RSM). Subsequently, preprocessing of the sky color bleeding is based on the radiosity technique to give the sky color effect to the virtual objects as well as the real ones. Through designing a test AR set-up and applying software and hardware the goal of a robust generation of realistic virtual objects with effect of sky color is achieved.

Statistics of the Sunyaev-Zel'dovich effect power spectrum

Using large numbers of simulations of the microwave sky, incorporating the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect due to clusters, we investigate the statistics of the power spectrum at microwave frequencies between spherical multipoles of 1000 and 10000. From these virtual sky maps, we find that the spectrum of the SZ effect has a larger standard deviation by a factor of 3 than would be expected from purely Gaussian realizations, and has a distribution that is significantly skewed towards higher values, especially when small map sizes are used. The standard deviation is also increased by around 10 percent compared to the trispectrum calculation due to the clustering of galaxy clusters. We also consider the effects of including residual point sources and uncertainties in the gas physics. This has implications for the excess power measured in the CMB power spectrum by the Cosmic Background Imager and BIMA experiments. Our results indicate that the observed excess could be explained using a lower value of $\sigma_8$ than previously suggested, however the effect is not enough to match $\sigma_8=0.825$. The uncertainties in the gas physics could also play a substantial role. We have made our maps of the SZ effect available online.

Outdoor Illuminance Levels in the Tropics and their Representation in Virtual Sky Domes

This paper presents two ways to predict outdoor illuminance levels in the tropics. The first one is based on calculations mainly following the recent CIE/ISO Standard General Sky. The second one applies Virtual Sky Domes (VSD) and Virtual Sky and Sun Domes (VSSD) generated for use with standard light simulation software. The accuracy of the VSD and VSSD methods in predicting illuminance levels with and without sunlight is evaluated and shown to be very close to the calculations. Thus, VSD and VSSD can eventually become useful tools to be added into standard lighting simulation software.

Enabling Grid technologies for Planck space mission

Planck, the ESA satellite aimed at mapping the microwave sky through two complete sky surveys, will fly in 2007. It is an extremely demanding space mission in terms of computing power and data storage. Planck simulations mimic the whole mission starting from a virtual sky (ideal or contaminated by introducing several noise sources). Their main goal is the validation of the acquisition and reduction procedure that will be used to build the final scientific data during the operative phase of the mission. The Grid technology seems to be a promising answer to data storage and processing needs of the satellite. In the framework of the EGEE grid infrastructure, we managed to run a number of experiments aimed at designing and defining an application specific environment for the simulation software and data sharing. Our successful experiments demonstrate that the “gridification” of Planck pipelines is not only possible but even extremely convenient in terms of data processing speed and data sharing.

Evaluation of Virtual Sky Domes for the Prediction of Daylight Performance with Radiosity-based Light Simulation Software

A Virtual Sky Dome (VSD) is a computational model of a hemisphere resembling the daylight conditions of a particular location, date and time1. It comprises of 145 point light sources, whose individual properties can be adjusted automatically to match the sky luminance distribution as defined by the current set of 15 standard skies2. VSD's can be formatted into any CAD-based lighting simulation software format, thus extending the range of simulation tools for daylight analysis beyond the commonly used software RADIANCE. This paper evaluates the accuracy of the VSD method for the prediction of daylight performance with the Radiosity-based light simulation software LIGHTSCAPE. Methodologically a simulation that used RADIANCE was compared against a simulation using VSD within the software LIGHTSCAPE. The former was based on a published case, which documents Daylight Factors in a reference room across all 15 sky types3. This case is referred to as reference case. LIGHTSCAPE's built-in sky types however follow the obsolete sky standard4, thus offering only a limited set of clear and overcast skies. The VSD method was now applied to create the 15 sky types for LIGHTSCAPE. Subsequently simulations for the reference room have been performed and Daylight Factors obtained. A comparison of Daylight Factors between the reference and VSD case shows a high accordance, the mean deviation over all sky types and locations is less than 2%. It can be concluded that a simulation, using Virtual Sky Domes for Radiosity-based simulation tools, predicts the daylight performance as accurate as the reference case.

A Method to Construct Virtual Sky Domes for Use in Standard CAD-based Light Simulation Software

A Virtual Sky Dome (VSD) is a computational model of a hemisphere resembling the daylight conditions of a particular location, date and time. VSD's allow users of standard CAD-based simulation software to simulate architecture and assess daylight performance criteria making full use of the 15 standard sky luminance distribution models, which have just recently been accepted as a CIE standard [1]. This paper introduces the method to construct VSD. Prior to this any daylight simulation using standard CAD based light simulation software was limited to a smaller set of standard skies: clear, overcast and intermediate with non-changeable parameters as in the case of the software Lightscape. The all-weather-sky tool developed for the software Radiance follows the sky definitions defined by Perez. Neither of these tools considers the recently developed standard of 15 sky types, which is to replace previous standards[2] to further differentiate the skies to better match the real daylight conditions. This is of particular significance for predominately cloudy regions like Singapore, where a wide range of overcast and intermediate skies with significant different luminance distributions occur. A VSD is a CAD model of the hemisphere comprising 145 point lights of controllable parameters, each one sitting in the centre of a particular sky patch. Their luminous flux is derived from the luminance of the individual sky patch calculated using Kittler's equation[3]. A computational method has been developed that creates a VSD for a given sky type based on the input of solar azimuth and elevation, hence representing a particular time and location. This paper explains the method and shows results using VSD's to simulate daylight with the standard CAD-based light simulation software Lightscape.

The virtual sky is not the limit: ethics in virtual reality

The allegedly novel technology of virtual reality (VR) introduces a number of difficult moral questions. In spite of the apparent novelty of the technology, at least some of these questions can be shown to be variations on more familiar moral problems. However, familiar or not, many of the moral problems raised by VR need urgent attention and discussion.