Mojtaba Navvab

The Virtual Lighting Laboratory: Per-pixel Luminance Data Analysis

T he Virtual Lighting Laboratory (VLL) is an image based lighting analysis tool and methodology, which operates with physically-based High Dynamic Range (HDR) digital images. Through appropriate modeling, rendering, and image technology, physically based renderings and HDR Photographs can be used to extract per-pixel lighting information. Extraction of per-pixel luminance data is done by converting the RGB values in each pixel of HDR imagery (that is, an RGBE image, also known as hdr) into CIE XYZ data using the CIE 1931 Standard Colorimetric Observer Functions. A detailed documentation of the study can be found in (Inanici 2004). In VLL, per-pixel lighting data extracted from physically based renderings is processed through mathematical and statistical operations to perform lighting analysis with detail, flexibility and rigor that may be infeasible or impossible with the traditional lighting analysis approaches. The analysis in the VLL focus on the investigations of the following criteria to achieve the intended visual effect, performance, and comfort 1. ADEQUATE QUANTITY OF LIGHT 2. SUITABLE SPATIAL DISTRIBUTION OF LIGHT 3. SUFFICIENT DIRECTIONALITY OF LIGHT 4. ABSENCE OF GLARE; AND 5. SUFFICIENT SPECTRAL CONTENT OF LIGHT The analyses in this paper have been limited to the study of the distribution and directionality of light. They are not exhaustive in nature; rather, they highlight some of the per-pixel analysis capabilities.

Experimental development of efficacious task source relationships in interior lighting applications

The authors report on a series of full-scale photometric simulation studies conducted to examine the luminous environment within work stations used in typical office environments. The objective of these experimental studies was to develop explicit geometric relationships between a visual task and a lighting layout that maintains visual quality and minimizes power required. A broad range of ceiling integrated general and task lighting systems were examined in terms of their ability to maintain contrast and illuminance across the work plane. For each lighting system studied a range of furniture systems was employed to determine potential obstruction effects as a function of orientation and position in respect to a particular lighting layout. Experimental data expressed in terms of luminance contrast and illuminance across the task plane show the importance of developing and specifying explicit geometric relationships between a visual task and a lighting system layout. Data illustrating the variations in lighting quality as a function of geometry and task configuration are presented.<<ETX>>

Evaluation of historical museum interior lighting system using fully immersive virtual luminous environment

Saint Rocco Museum, a historical building in Venice, Italy is used as a case study to explore the performance of its’ lighting system and visible light impact on viewing the large size art works. The transition from threedimensional architectural rendering to the three-dimensional virtual luminance mapping and visualization within a virtual environment is described as an integrated optical method for its application toward preservation of the cultural heritage of the space. Lighting simulation programs represent color as RGB triplets in a devicedependent color space such as ITU-R BT709. Prerequisite for this is a 3D-model which can be created within this computer aided virtual environment. The onsite measured surface luminance, chromaticity and spectral data were used as input to an established real-time indirect illumination and a physically based algorithms to produce the best approximation for RGB to be used as an input to generate the image of the objects. Conversion of RGB to and from spectra has been a major undertaking in order to match the infinite number of spectra to create the same colors that were defined by RGB in the program. The ability to simulate light intensity, candle power and spectral power distributions provide opportunity to examine the impact of color inter-reflections on historical paintings. VR offers an effective technique to quantify the visible light impact on human visual performance under precisely controlled representation of light spectrum that could be experienced in 3D format in a virtual environment as well as historical visual archives. The system can easily be expanded to include other measurements and stimuli.

Using Multimedia Interactive E-teaching in Color Science

Abstract Color is becoming a key issue in many e-commerce products. This made it necessary to develop a color course easily accessible from the Internet or distributed on CD-ROM. This article describes the advantages of the electronic approach – compared to class-room demonstrations – to bring the fundamentals of colorimetry to the student with the help of demonstrations.

Reducing hospital noise with sound acoustic panels and diffusion: a controlled study

Noise has been identified as a major stressor in hospitals,1 ,2 with ambient noise frequently exceeding recommended levels set by the WHO3 and reportedly as high as alarm clocks.4 ,5 Although hospitals frequently attempt to reduce noise through traditional methods such as shielding the patient (eg, closing doors), moving equipment or altering staff behaviours, these approaches disrupt workflow and ignore the realities of sound generation required in modern hospitals, which potentially limits their impact on quality and patient safety. An unexplored method of reducing hospital noise borrowed from other industries is to use sound acoustic panels that diffuse noise rather than attempt to eliminate it.6 We performed a pilot study to determine whether strategically placed, sound acoustic panels applied in hospitals would acutely reduce noise in hallways adjacent to patient rooms. If true, this option could serve as an architectural design solution to enhance patient care and experience during hospitalisation. We conducted an observational, controlled study assessing sound levels on an active inpatient telemetry unit. Due to physical nature of sound acoustic panels, patients and staff were not blinded. Placement of panels and acoustic equipment met all institutional building management policies and national codes (figure 1). The inpatient telemetry unit is organised as two central parallel hallways with architecturally identical patient rooms on both sides. Walls and floors were hard surfaces designed for ease …

Contrast potential, an assessment technique using large solid angle illuminance measurements

The authors describe a technique for assessing the luminous contrast within lighting environments. This technique uses large solid angle measurements of both vertical and horizontal illuminance on the work plane, and is based on combining the horizontal and vertical illuminance measurements with a simple expression. This illuminance function was compared with the luminance contrast measurements obtained with a luminance contrast meter. Analysis of the experimental data indicates a strong correlation between the illuminance-based procedure and data obtained with the meter. The assessment of contrast based on large solid angle measurements of illuminance is also described.<<ETX>>

Strategies to decrease future electricity loads in institutional buildings

As part of the University of Michigans lighting research program, a variety of building characteristics and electric consumption patterns were documented. This information was combined with field and laboratory test results for alternative lighting design and control strategies. The results of these alternative comparisons were applied toward University guidelines and recommendations for energy management and lighting system retrofit. The authors discuss the most significant aspects of the data collection and implementation phases as well as the results of the investigation of alternative design solutions.<<ETX>>

Lighting distribution affects pedestrians' sense of security

The greatest obstacle to a pedestrians Sense of Security (SoS) is lack of lighting. This research analyzes lighting characteristics which affect a pedestrians SoS, including how lighting distribution changes perception, to design lighting for night-time walking that maximizes the SoS without increasing energy consumption.

Opinion: Simulation in lighting design and research

Simulation in architectural lighting design, research and education is essential. The basic question is: how effective is the simulation of design ideas in achieving the objectives? Some scholars believe that the objectives and the measurement system should be decided before efforts to achieve the objectives are made. Only then is a judgement made of the achievement’s value. Others, perhaps working in other than achievement-oriented cultures and educational settings, would argue for a more open approach in which the objectives emerge during the design of the simulation. Both perspectives are valid within their own logic and may be seen as mutually exclusive. Whether that is the case or not, some form of evaluation is certainly important for the learning we wish to promote, even if this is accomplished only during the process of design. Valid and sustained evaluation is more important still for the profession. This could be accomplished by elaborate objectivebased, achievement-oriented, quantitative, longitudinal study, or by more informal, subjective and participatory assessment. Such evaluation will help practitioners, designers, educators and theorists build a stronger case for simulation as well as head off opponents who seem all too eager to spot false pitfalls in these endeavours. It is perhaps in this area that some of the greatest differences in opinion on simulation exist. Simulation combines design experiences with technical assumptions. Combining different simulation techniques can remarkably accelerate decision-making and evaluation by designers. The main emphasis is the application of such techniques to lighting design and research, to influence architectural lighting education both academically and in practice, whether viewed as tactical (refinements of existing metrics) or strategic (the identification of big questions in a given research area). Researchers continually seek to arrive at design guidelines that include high-precision quantitative and qualitative analysis and evaluation using simulation. The effectiveness of simulation in achieving its objectives is dependent upon the evaluation techniques and methods used. Simulation is an attempt to abstract and reproduce the central features of a complex system for the purpose of understanding, experimenting with, and predicting the behaviour of the system. Simulation is the most complex activity ever undertaken by humans; it is the only one where its practitioners habitually make so many mistakes without (usually) being accused of incompetence. Simulation is an anticipatory view of a system in a low-risk situation. The main objective of simulation is to represent a system that behaves similarly to potential real world conditions. Simulations as evaluation techniques do challenge humans’ visual perception and physical sensations. They are used for hands-on investigation and re-creation, or just for the pleasure of looking at them (e.g. computer games and simulated historical or futuristic scenes with real-time shadows and massive lighting in virtual reality). They have integrity of their own. They bring enormous, impressive, grandiose environmental and lighting design issues down to a very understandable level of real world settings that can be evaluated by humans.

Measured and simulated room acoustic characteristics in three concert halls with unique architectural geometry using beamforming techniques

Sound reflections and time delay between direct and reflected sounds are key variables that shape and contribute to the acoustic quality and listening experience within concert halls. To demonstrate these architectural space characteristics from a designer’s standpoint, three internationally well-known halls are simulated and selectively measured for their acoustic characteristics utilizing beamforming techniques. The results are analyzed given recommended procedures within ISO3382 standards. Realistic computer reconstructions of these concert halls provides the opportunity to examine the sound quality of each and the differences in their performance using the latest sound quality measures. Known indicators such as reverberation time, sound strength, center time, echo, clarity-definition for speech and music, speech transmission index and articulation loss are used to show important acoustical features of these halls. The simulated and measured results provide supportive data toward the recognition of key...