Papers by Mehlika Inanici
Lighting Research & Technology, Jul 2, 2022
Sky models in daylight simulations represent the luminance variation across the sky-dome for diff... more Sky models in daylight simulations represent the luminance variation across the sky-dome for different locations, dates, times and weather conditions, but skies are typically modelled as colourless. Recent studies explore techniques for incorporating the spectral content of daylighting in simulations. This paper provides an evaluation of the existing spectral sky models in lighting simulation software. The comparisons are made between the available mathematical sky models and naturally occurring skies that were recorded using high dynamic range photography and spectrophotometric measurements. The results show that recently developed sky models present progress compared to colourless sky models, but further research is needed to accurately simulate daylight spectra.
CAADRIA proceedings
Architects often use two-dimensional media to represent, visualise, and study the three-dimension... more Architects often use two-dimensional media to represent, visualise, and study the three-dimensional qualities of un-built spaces. Knowledge of pictorial cues is a powerful design tool that can be used to enhance the spatial qualities of built environments. This paper draws from the recent developments in computer graphics (physically based renderings and perceptually based tone mapping techniques) and demonstrates the utilisation of a computational framework to generate pictorial spaces that can mimic perceptual reality. Computer simulation and psychophysical research methodologies are employed to examine the relationship between the lighting patterns introduced by architectural confi gurations and their impacts on depth perception. The research demonstrates that physically and perceptually based renderings can be used to study depth perception; and luminance contrast in an architectural scene is an effective pictorial cue that increases the perceived spatial depth.
Compared with illuminance-based metrics, luminancebased metrics and evaluations provide better un... more Compared with illuminance-based metrics, luminancebased metrics and evaluations provide better understandings of occupant visual experience. However, it is computationally expensive and time consuming to incorporate luminance-based metrics into architectural design practice because annual simulations require generating a luminance map at each time step of the entire year. This paper describes the development of a novel prediction model to generate annual luminance maps of indoor space from a subset of images by using deep neural networks (DNNs). The results show that by only rendering 5% of annual luminance maps, the proposed DNNs model can predict the rest with comparable accuracy that closely matches those highquality point-in-time renderings generated by Radiance (RPICT) software. This model can be applied to accelerate annual luminance-based simulations and lays the groundwork for generating annual luminance maps utilizing High Dynamic Range (HDR) captures of existing environments.
Building Simulation Conference Proceedings
LEUKOS
The use of daylight in the built environment is often preferred to artificial light sources as it... more The use of daylight in the built environment is often preferred to artificial light sources as its successful application can provide visual comfort and satisfaction along with the potential for significant energy savings. Exposure to daylight is also the primary source for stimulus that establishes a healthy day/night cycle in all living organisms. This is known as circadian rhythm. Newly discovered photoreceptors (intrinsically photosensitive retinal ganglion cells-ipRGC) within the mammalian eye, including humans, are specifically linked to the portion of the brain responsible for maintaining a healthy circadian rhythm. This discovery has led to a new subject area in the field of lighting design focused on controlling the spectrum of light that these photoreceptors are sensitive to. Currently, work in the field of circadian lighting design is concentrated on the use of artificial light sources for circadian stimulus. This is largely due to the advent of the widespread use of LED technology, which has proven that it can be a significant source of light that can delay or advance the circadian clock. The use of daylight to provide circadian stimulus has been a given in this field of design, however, there has not been very much research into how the built environment affects our ability to effectively receive this stimulus from daylight. In this research, the groundwork is established to start to create a set of guidelines to help architects and designers maximize the potential for daylight to provide circadian stimulus at the earliest stages of a project. This is accomplished through a series of lighting simulations that explore and test various architectural parameters that affect daylight-driven circadian lighting, with simultaneous consideration given to photopic lighting availability and visual comfort. The architectural parameters tested in this study included window head height, building orientation, shading devices, visual obstructions to the sky, and room depth. The results show that informed design decisions could maximize circadian potential in a given space, while achieving visually satisfactory luminous environments.
Spectral properties of daylight surpasses any other light source. Its dynamic intensity and spect... more Spectral properties of daylight surpasses any other light source. Its dynamic intensity and spectra across the full spectrum facilitates sustainable daylighting practices, produces best color rendition, and regulates circadian rhythms in all living beings. However, simulation models do not typically include spectral variability; daylight is modelled as a uniform, equal energy white source. In this paper, tristimulus calibration procedures are utilized to create spectrally accurate High Dynamic Range (HDR) photographs. HDR photographs of skies are collected and utilized as an input to image based lighting (IBL) simulations. The impact of color variations across the sky dome and between different sky conditions are studied. Per-pixel photopic luminances, tri-stimulus chromatic distributions, Correlated Color Temperatures (CCT) and circadian luminance and illuminance values are quantified for image-based daylighting simulations, and compared with standard colorless Perez skies.
The deliberate utilisation of daylight has been discussed as an outstanding element of the design... more The deliberate utilisation of daylight has been discussed as an outstanding element of the design of Hagia Sophia in Istanbul starting with late antique sources, and continued through the centuries up to our day. Computational simulation allows to reconstruct this illumination. This - for the first time - offers a means to relate historical descriptions and modern hypotheses with daylight as a physical phenomenon, but requires a sound methodological basis to provide valid results. Bidirectional photon-mapping is demonstrated to predict the propagation of light in the architectural space, characterised by complexity with regard to its geometry as well as the optical properties of its boundaries. The latter must be reconstructed in their original condition, eliminating modifications of the original building composition as well as deterioration of the material and finishes of building elements. The description of the latter's irregular properties suggests data-driven modelling base...
Measuring the luminous environment enables researchers and practitioners to study perception and ... more Measuring the luminous environment enables researchers and practitioners to study perception and visual comfort in existing environments in order to decipher the components that contribute to good or problematic lighting characteristics. High dynamic range photography is commonly used to study visual perception and comfort. This paper presents new findings and specific methods of capturing interior scenes that may include peaks caused by a direct view of the sun and specular reflections. Methods are tested to improve the range of luminance values that can be captured, and new guidelines are proposed to improve the accuracy of computed visual comfort indices.
Architects often use two-dimensional media to represent, visualise, and study the three-dimension... more Architects often use two-dimensional media to represent, visualise, and study the three-dimensional qualities of un-built spaces. Knowledge of pictorial cues is a powerful design tool that can be used to enhance the spatial qualities of built environments. This paper draws from the recent developments in computer graphics (physically based renderings and perceptually based tone mapping techniques) and dem- onstrates the utilisation of a computational framework to generate pic- torial spaces that can mimic perceptual reality. Computer simulation and psychophysical research methodologies are employed to examine the relationship between the lighting patterns introduced by architec- tural confi gurations and their impacts on depth perception. The research demonstrates that physically and perceptually based renderings can be used to study depth perception; and luminance contrast in an archi- tectural scene is an effective pictorial cue that increases the perceived spatial depth.
This paper describes the development of a new tool called hdrscope that enables users to perform ... more This paper describes the development of a new tool called hdrscope that enables users to perform qualitative and quantitative lighting analysis via perpixel methods. Using a simulated and photographically captured lab space as a case study, per-pixel analysis methods are described, challenges associated with per-pixel lighting analysis are discussed, and hdrscope analysis techniques are demonstrated. hdrscope is intended to lower the entry barrier for lighting professionals, and to facilitate the utilization of lighting analysis in early design and development stages as well as post occupancy. It also provides a user friendly tool for lighting experts while filling in the gaps among the current lighting analysis tools.
When people see the world, their eyes perceive brightness (the subjective feeling of luminance), ... more When people see the world, their eyes perceive brightness (the subjective feeling of luminance), not illuminance. Luminance-based metrics have been increasingly used in lighting practices. Unfortunately, traditional spot luminance meters make it very hard if not impossible to measure common non-uniform and dynamic luminance distributions, such as those produced by daylight. High Dynamic Range Imaging (HDRI) allows measurement of millions of luminance points across a scene within 1-2 minutes. Aided by affordable HDR photography hardware and software, it is possible for lighting professionals to effectively measure spatial and temporal luminance distribution of daylit environments in extraordinarily high resolution. In the past decade, there has been an increasing use of HDR imaging in daylighting
Annual luminance maps provide meaningful evaluations for occupants’ visual comfort, preferences, ... more Annual luminance maps provide meaningful evaluations for occupants’ visual comfort, preferences, and perception. However, acquiring luminance maps require labor-intensive and time-consuming simulations or impracticable long-term field measurements. This paper presents a novel method to accelerate annual luminancebased evaluations utilizing a deep neural network (DNN). From a small subset (5%) of high dynamic range (HDR) imagery, our method can predict annual panoramic luminance maps (with 360-degrees horizontal and 180degrees vertical field of view) within an hour. Unlike the fixed camera viewpoint of perspective or fisheye projections that are commonly used in daylighting evaluations, panoramas allow full degree-of-freedom in camera roll, pitch, and yaw, thus providing a robust source of information for an occupant’s visual experience in a given environment. The DNN predicted high-quality panoramas are validated against Radiance RPICT renderings using a series of quantitative and q...
Recent studies have demonstrated that the spectral content of light at typical interior daylight ... more Recent studies have demonstrated that the spectral content of light at typical interior daylight levels affects human circadian rhythms. Lighting simulation tools are developed, used, and validated mainly for computing the visual aspects of lighting. This paper demonstrates utilization of a multi-spectral simulation method that can be employed to design and analyse circadian lighting in built environments. The methodology is context-based, allowing the researchers and designers to consider local skies, exterior context, glazing optics, surface materials, interior design, and viewer location.
Lighting Research & Technology, 2018
The human ocular system functions in a dual manner. While the most well-known function is to faci... more The human ocular system functions in a dual manner. While the most well-known function is to facilitate vision, a growing body of research demonstrates its role in resetting the internal body clock to synchronize with the 24-hour daily cycle. Most research on circadian rhythms is performed in controlled laboratory environments. Little is known about the variability of circadian light within the built and natural environments. Currently, very few specialized devices measure the circadian light, and they are not accessible to many researchers and practitioners. In this paper, tristimulus colour calibration procedures for high dynamic range photography are developed to measure circadian lighting. Camera colour accuracy is evaluated through CIE trichromatic (XYZ) measurements; and the results demonstrate a strong linear relationship between the camera recordings and a scientific-grade colorimeter. Therefore, it is possible to correct for the colour aberrations and use high dynamic range...
Pictorial depth cues are the visual information gathered from three dimensional scenes, and used ... more Pictorial depth cues are the visual information gathered from three dimensional scenes, and used to recover the third dimension of depth from two dimensional retinal images. Pictorial depth cues are also used to create the illusion of depth on pictorial ...
LEUKOS, 2010
New research in daylighting metrics and developments in validated digital High Dynamic Range (HDR... more New research in daylighting metrics and developments in validated digital High Dynamic Range (HDR) photography techniques suggest that luminance based lighting controls have the potential to provide occupant satisfaction and energy saving improvements over traditional illuminance based lighting controls. This paper studies occupant preference and acceptance of patterns of luminance using HDR imaging and a repeated measures design methodology in a daylit office environment. Three existing luminance threshold analysis methods [method1: predetermined absolute luminance threshold (for example, 2000 cd/m 2), method2: scene based mean luminance threshold, and method3: task based mean luminance threshold] were studied along with additional candidate metrics for their ability to explain luminance variability of 18 participant assessments of 'preferred' and 'just disturbing' scenes under daylighting conditions. Per-pixel luminance data from each scene were used to calculate Daylighting Glare Probability (DGP), Daylight Glare Index (DGI), and other candidate metrics using these three luminance threshold analysis methods. Of the established methods, the most consistent and effective metrics to explain variability in subjective responses were found to be; mean luminance of the task (using method3; adj r 2 ϭ 0.59), mean luminance of the entire scene (using method2; adj r 2 ϭ 0.44), and DGP using 2000 cd/m 2 as a glare source identifier (using method1; adj r 2 ϭ 0.41). Of the 150 candidate metrics tested, the most effective was the 'mean luminance of the glare sources', where the glare sources were identified as 7* the mean luminance of the task position (adj r 2 ϭ 0.64).
Since its construction in the sixth century, Hagia Sophia has been praised for its lighting. Whil... more Since its construction in the sixth century, Hagia Sophia has been praised for its lighting. While some aspects of its illumination can be studied in the present building, the totality of its primal appearance has been lost due to supporting measures, additions, and later changes. An attempt is made to analyse this illumination, and to understand the day-lighting concepts inherent in Hagia Sophia's outstanding architecture, employing computational simulation based on the reconstruction of the building's geometry at the time of its second dedication. Accounted for are the original distribution and properties of the surfaces enclosing the architectural space, including the detailed marble decoration; the original gilding of sculptural elements; and the optically complex gold mosaics. Daylight simulation under a synthetic sky with varying solar geometries and cloud coverage reveals differences between the historic and present states, e.g. higher diffuse illumination originating...
Research Methods in Building Science and Technology
Uploads
Papers by Mehlika Inanici