A review of East Asian reports of aurorae and comets circa AD 775

Given that a strong 14C variation in AD 775 has recently been suggested to be due to the largest solar flare ever recorded in history, it is relevant to investigate whether celestial events observed around that time may have been aurorae, possibly even very strong aurorae, or otherwise related to the 14C variation (e.g. a suggested comet impact with Earth's atmosphere). We critically review several celestial observations from AD 757 to the end of the 770s, most of which were previously considered to be true, and in some cases, strong aurorae; we discuss in detail the East Asian records and their wording. We conclude that probably none among the events after AD 770 was actually an aurora, including the event in AD 776 Jan, which was misdated for AD 774 or 775; the observed white qi phenomenon that happened "above the moon" in the south-east was most probably a halo effect near the full moon - too late in any case to be related to the 14C variation in AD 774/5. There is another report of a similar (or identical) white qi phenomenon "above the moon", reported just before a comet observation and dated to AD 776 Jan; the reported comet observed by the Chinese was misdated to AD 776, but actually sighted in AD 767. Our critical review of East Asian reports of aurorae circa AD 775 shows some very likely true Chinese auroral displays observed and reported for AD 762; there were also several events prior to AD 771 that may have been aurorae but are questionable.Comment: 15 pages with 4 figure

Efficient rendering of atmospheric phenomena

Journal ArticleRendering of atmospheric bodies involves modeling the complex interaction of light throughout the highly scattering medium of water and air particles. Scattering by these particles creates many well-known atmospheric optical phenomena including rainbows, halos, the corona, and the glory. Unfortunately, most radiative transport approximations in computer graphics are ill-suited to render complex angularly dependent effects in the presence of multiple scattering at reasonable frame rates. Therefore, this paper introduces a multiple-model lighting system that efficiently captures these essential atmospheric effects. We have solved the rendering of fine angularly dependent effects in the presence of multiple scattering by designing a lighting approximation based upon multiple scattering phase functions. This model captures gradual blurring of chromatic atmospheric optical phenomena by handling the gradual angular spreading of the sunlight as it experiences multiple scattering events with anisotropic scattering particles. It has been designed to take advantage of modern graphics hardware; thus, it is capable of rendering these effects at near interactive frame rates

The 3D Acid Test: Perceptual Attributes vs Renderable Elements

The Romantics artificially embellished light and colour to convey emotion in their artworks. Light and colour were used to ignite a sense of enchantment and to stir an emotional response from the viewer. 3D software operates within this established visual tradition: current digital artistic representation involves a similarly embellished reality. This is a testament to what we continually want to see and how we would like to be visually entertained and informed, and physically based 3D renderer Arnold provides the tools for this continuation. Inherent in the world’s most-used 3D rendering programme Arnold are light and surface attributes which have been programmed to be adjustable to achieve myriad visual results. These attributes, however, have a history rooted in computer graphics’ plight for realism by abiding by the laws of optics and physics in their creation. However, these tools were designed with an arbitrarily chosen set of limits: arbitrary in the sense that these limits define a range of possibility to be used conveniently by the artist rather than by necessity or intrinsic nature. Johann Goethe (b. 1749), a Romantic poet, was critical of how light and colour were used by his artistic peers. He was dissatisfied by the embellishment of light and colour in paintings, and endeavoured to know exactly what was happening when he looked at things. Goethe conducted a series of experiments on light and colour, which resulted in his book Theory of Colours (1810, trans. Charles Eastlake, 1840). In my study, using Theory of Colours as a guideline, I have recreated fifty of Goethe’s experiments in 3D. I explore the fundamentals of Arnold as it was created, revealing the benchmark of current achievable 3D realism. Ten of these experiments are discussed in this paper. These experiments, in my judgment, are more applicable to the scope of phenomena replicable with a renderer, and scale the vast number of Goethe’s experiments in Theory of Colours to a reasonable set of testable conditions. The human perception of reality is the baseline against which rendering qualities must be judged, and Goethe’s experiments are replicable. As an instructor of 3D rendering, I aim to instill in my students the knowledge gained from this study, with the intention to empower the students with their own rendering so that they may make informed, predictable decisions

CREATING CONVINCING AND DRAMATIC LIGHT TRANSITIONS FOR COMPUTER ANIMATION

Lighting and atmospheric changes are complex phenomena that exist in nature; therefore replicating them using computer graphics can be quite challenging. Subtle changes in light conditions can greatly affect the mood or perception of the viewer and has been an important component of film making. With ever increasing technology and computing resources, filmmakers continue to strive to produce such complex effects that enhance their storytelling. Light transition (e.g.; day to night), continuously moving light sources, and dramatic change in seasons have been the focus of experimentation for many films. Most studios have therefore developed their own pipeline to create such effects. This thesis describes some simple and efficient observations and techniques to create such convincing lighting transitions

Advanced techniques for atmospheric effects

Over the last few years, open world videogames have been gaining lots of interest in the gaming industry. Open world videogames not only allow the player to freely roam over a vast terrain but also aim to recreate a believable dynamic world. Thus, one of the basic elements that such a videogame should feature is a day and night cycle. In this thesis, all of the intricacies that are involved in developing a physically based day and night cycle solution in a real-time rendering context are discussed. The main topics that will be covered are atmosphere rendering, celestial bodies positioning, celestial bodies rendering and nighttime scenes rendering

Night rendering

Journal ArticleThe issues of realistically rendering naturally illuminated scenes at night are examined. This requires accurate models for moonlight, night skylight, and starlight. In addition, several issues in tone reproduction are discussed: eliminatiing high frequency information invisible to scotopic (night vision) observers; representing the flare lines around stars; determining the dominant hue for the displayed image. The lighting and tone reproduction are shown on a variety of models

Shedding light on GIS: A 3D immersive approach to urban lightscape integration into GIS

Geographic Information Systems (GIS) have the ability to map, model, and analyze real world data and phenomena, and yet visibility and lighting conditions are rarely considered or researched in Geographic Information Science (GISci). Lighting technologies have been created and implemented to overcome the darkness of night and other issues of visibility, and in no place is that more evident than urban areas. Though not researched heavily in GIS, it is now possible to model and analyze lighting of the built environment using GIS, 3D modeling and rendering software. This thesis explores the night time urban lightscape, its spatial aspects and contribution to place as well as its incorporation into GIS and GISci. To capture lighting and its multi-dimensional properties, a 3D model was created of the built environment of Morgantown, WV, USA, including the West Virginia University (WVU) campuses and their exterior lighting. The model was completed through the coupling of ESRI\u27s CityEngine and E-on software\u27s LumenRT4 Geodesign plug-in. Lighting data was obtained through the WVU Department of Construction and Design in the form of a CAD map. After geo-referencing CAD-based exterior lighting data, a raster lighting analysis of WVU\u27s Evansdale Campus was produced to identify under-lit areas. These areas were then redesigned using a lighting design tool and incorporated 3D modeling, GIS, and procedural rule-based modeling. An original workflow was designed consisting of ArcGIS, SketchUp, CityEngine, and LumenRT 4 Geodesign. Lighting scenarios were subsequently viewed and experienced through immersive technologies

Enabling a High Throughput Real Time Data Pipeline for a Large Radio Telescope Array with GPUs

The Murchison Widefield Array (MWA) is a next-generation radio telescope currently under construction in the remote Western Australia Outback. Raw data will be generated continuously at 5GiB/s, grouped into 8s cadences. This high throughput motivates the development of on-site, real time processing and reduction in preference to archiving, transport and off-line processing. Each batch of 8s data must be completely reduced before the next batch arrives. Maintaining real time operation will require a sustained performance of around 2.5TFLOP/s (including convolutions, FFTs, interpolations and matrix multiplications). We describe a scalable heterogeneous computing pipeline implementation, exploiting both the high computing density and FLOP-per-Watt ratio of modern GPUs. The architecture is highly parallel within and across nodes, with all major processing elements performed by GPUs. Necessary scatter-gather operations along the pipeline are loosely synchronized between the nodes hosting the GPUs. The MWA will be a frontier scientific instrument and a pathfinder for planned peta- and exascale facilities.Comment: Version accepted by Comp. Phys. Com