Closed-Form Expressions for Irradiance from Non-Uniform Lambertian Luminaires Part I: Linearly-Varying Radiant Exitance

We present a closed-form expression for the irradiance at a point on a surface due to an arbitrary polygonal Lambertian lurninaire with linearly-varying radiant exitance. The solution consists of elementary functions and a single well-behaved special function that can be either approximated directly or computed exactly in terms of classical special functions such as Clausen's integral or the closely related dilogarithm. We first provide a general boundary integral that applies to all planar luminaires and then derive the closed-form expression that applies to arbitrary polygons, which is the result most relevant for global illumination. Our approach is to express the problem as an integral of a simple class of rational functions over regions of the sphere, and to convert the surface integral to a boundary integral using a generalization of irradiance tensors. The result extends the class of available closed-form expressions for computing direct radiative transfer from finite areas to differential areas. We provide an outline of the derivation, a detailed proof of the resulting formula, and complete pseudo-code of the resulting algorithm. Finally, we demonstrate the validity of our algorithm by comparison with Monte Carlo. While there are direct applications of this work, it is primarily of theoretical interest as it introduces much of the machinery needed to derive closed-form solutions for the general case of luminaires with radiance distributions that vary polynomially in both position and direction

International Lighting in Controlled Environments Workshop

Lighting is a central and critical aspect of control in environmental research for plant research and is gaining recognition as a significant factor to control carefully for animal and human research. Thus this workshop was convened to reevaluate the technology that is available today and to work toward developing guidelines for the most effective use of lighting in controlled environments with emphasis on lighting for plants but also to initiate interest in the development of improved guidelines for human and animal research

Performance modelling for advanced envelope systems.

SIGLEAvailable from British Library Document Supply Centre- DSC:DXN055168 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Measuring and understanding light in real life scenarios

Lighting design and modelling (the efficient and aesthetic placement of luminaires in a virtual or real scene) or industrial applications like luminaire planning and commissioning (the luminaire's installation and evaluation process along to the scene's geometry and structure) rely heavily on high realism and physically correct simulations. The current typical approaches are based only on CAD modeling simulations and offline rendering, with long processing times and therefore inflexible workflows. In this thesis we examine whether different camera-aided light modeling and numerical optimization approaches could be used to accurately understand, model and measure the light distribution in real life scenarios within real world environments. We show that factorization techniques could play a semantic role for light decomposition and light source identification, while we contribute a novel benchmark dataset and metrics for it. Thereafter we adapt a well known global illumination model (i.e. radiosity) and we extend it so that to overcome some of its basic limitations related to the assumption of point based only light sources or the adaption of only isotropic light perception sensors. We show that this extended radiosity numerical model can challenge the state-of-the-art in obtaining accurate dense spatial light measurements over time and in different scenarios. Finally we combine the latter model with human-centric sensing information and present how this could be beneficial for smart lighting applications related to quality lighting and power efficiency. Thus, with this work we contribute by setting the baselines for using an RGBD camera input as the only requirement to light modeling methods for light estimation in real life scenarios, and open a new applicability where the illumination modeling can be turned into an interactive process, allowing for real-time modifications and immediate feedback on the spatial illumination of a scene over time towards quality lighting and energy efficient solutions

The asymmetries of colour constancy as determined through illumination discrimination using tuneable LED light sources

PhD ThesisThe light reflected from object surfaces changes with the spectral content of the illumination. Despite these changes, the human visual system tends to keep the colours of surfaces constant, a phenomenon known as colour constancy. Colour constancy is known to be imperfect under many conditions; however, it is unknown whether the underlying mechanisms present in the retina and the cortex are optimised for the illuminations under which they have evolved, namely, natural daylights, or for particular objects. A novel method of measuring colour constancy, by illumination discrimination, is presented and explored. This method, unlike previous methods of measuring colour constancy, allows the testing of multiple, real, illuminations with arbitrary spectral content, through the application of tuneable, multi-channel LED light sources. Data from both real scenes, under real illuminations, and computer simulations are presented which support the hypothesis that the visual system maintains higher levels of colour constancy for daylight illumination changes, and in particular in the “bluer” direction, which are also the changes most frequent in nature. The low-level cone inputs for various experimental scenes are examined which challenge all traditional theories of colour constancy supporting the conclusions that higher-level mechanisms of colour constancy are biased for particular illuminations. Furthermore, real and simulated neutral (grey) surfaces are shown to affect levels of colour constancy. Moreover, the conceptual framework for discussing colour constancy with respect to emergent LED light sources is discussed.EPSR

Response adaptive modelling for reducing the storage and computation of RSS-based VLP

The precise (location) tracking of automated guided vehicles will be key in enlarging the productivity, efficiency and safety in the connected warehouse or production infrastructure. Combining the modest price tag, the adequate coverage and the potential centimetre accuracy makes Visible Light Positioning (VLP) systems appealing as replacements for the current, high-cost, tracking systems. Model-fingerprinting-based received signal strength (RSS) VLP enables the required accuracy. It requires an elaborate optical channel model fingerprinted in a fine-grained, and predefined positioning grid. Depending on the grid's granularity, constructing the fingerprint database demands a significant computation and storage effort. This paper employs response adaptive or sequential experimental design to form sparse channel models, vastly reducing the storage and computation. It is shown that model-fingerprinting-based RSS only requires modelling less than 1 percent of the grid points, in an elementary positioning cell. The sparse model can be re-evaluated as a way to cope with environment changeover. Model recomputation as a way of compensating for LED ageing is also studied

Controlled Environment Agriculture: A Pilot Project

The controlled-environment agricultural (CEA) project discussed in this report was first conceived for the Wildwood Air Force Station in Kenai, Alaska, in 1972. The region contained high unemployment and a U.S. Air Force Station that had just closed. The Kenai Native Association, Inc. (KNA), was to take possession of the Air Force Station through land transfers associated with the Alaska Native Claims Settlement Act, and this corporation was interested in expanding business and employment opportunities for local people. The University of Alaska Agricultural Experiment Station (AES) contacted KNA to determine if it had a facility which might be adaptable for use in a research and development program in controlled- 1 environment agriculture. It was determined that such a facility was available. Subsequently, AES and KNA contacted the General Electric Company (GE) in Syracuse, New York, to determine its interest in such a project. GE had extensive background in lighting technology and environmental control systems and the engineering capability to develop a total system for CEA production. It was agreed that GE would provide technological expertise and AES would provide horticultural and economic expertise for the growing and marketing of a variety of salad crops. KNA would manage the project, employ the nontechnical people, and provide the building. The Wildwood site was selected because it contained two buildings which were thought to be well suited for CEA production. One building would provide sufficient inside space for a 1/4-acre pilot production plant, nine small research modules , a laboratory , offices, a training area, and space for preparing the crop for shipping. A second building near the first contained three diesel generators which were to be converted to natural gas to provide power for the production facility.The Controlled Environment Agriculture Project at Wildwood Village, Kenai, Alaska, spanned a period of five years. During that time, three agencies: Kenai Native Association, Inc.; General Electric Company; and University of Alaska Agricultural Experiment Station , were responsible for the management, research, and production activities. Many persons from these agencies who participated in all phases of the project are acknowledged for their participation and support. This report summarizes work began in 1972 and concluded in 1977 on controlled-environment agriculture in facilities located at Wildwood Village, Kenai, Alaska, managed by the Kenai Native Association , Inc. The authors wish to express their appreciation to all those who have participated in the preparation of this bulletin. Particular acknowledgment is given to: Dr. Gerald Carlson, U.S .D.A., Beltsville, Maryland; Dr. Donald Dinkel, University of Alaska, Agricultural Experiment Station; Dr. Delbert Hemphill, Oregon State University ; John Monfor, Kenai Native Association, Inc.; Dr. Eion Scott, General Electric Company; and Dr. Norman Whittlesey, Washington State University, who thoroughly reviewed the contract document