The Relation between the Identification of Expression of Human Face and Semi-cylindrical Illuminance

The development of the lighting profession toward the third stage requires our attention shifting from the light on certain planes to the light distributions in 3D spaces. In this article, we propose a practical strategy to measure the local density of illumination in 3D scenes based on the zeroth-order of spherical harmonics decompositions of a high dynamic range (HDR) panoramic map. The basic functional principle of deriving illuminance density from HDR panoramic maps was presented, and hereinafter named as illuminance panoramic. Illuminance panoramic was compared with Cuttle’s approximated illuminance scalar, which is essentially a physical approximation of the average illumination over a sphere. To verify the measurements, the average illuminance over a sphere, approximated illuminance scalar, illuminance panoramic, cylindrical illuminance, semi-cylindrical illuminance, and horizontal illuminance were simulated via a model (probe in a sphere). The results indicate that the measurement of density of illumination using HDR panoramic maps has well coincided with its definition (i.e., the average illuminance over a sphere) while other illumination values vary with how the probes are located. The measurement theories were later verified using six HDR panoramic maps of real scenes. This research provides confidence in developing applications in mobile phones by capturing HDR panoramic maps to measure the density of illumination in 3D spaces.

Section: Model Probe In a Spherementioning

confidence: 99%

Theory and simulation of calculating local illuminance density based on high dynamic range panoramic maps

Liao

Zhang

et al. 2021

“…On the contrary, even at the lowest spatial region, such as 0.2 cpd, solid perception appeared, when the higher harmonics above the seventh were involved (Figure 4(d)). 3 …”

Section: ~Asc~s~ac~amentioning

confidence: 99%

Modeling effect of shading: New approach

Nameda

1990

One purpose of lighting is to help in the perception of an object's threedimensional form. The quality of lighting that does this is sometimes called 'the modelling effect of light' and it helps people see a solid form by creating a gradient of light across the surface of the object. This paper reports on a study which investigated the manner in which the pattern of light alone creates a sense of solidity in an object and relates this to the processing of visual information in terms of spatial frequencies. It is suggested that the human visual system identifies bands of spatial frequencies in the pattern of light incident on the retina and that the information is transmitted by two different visual pathways. Further, it is hypothesised that the perceived depth of a simple solid form can be predicted by considering the relationship between the information carried by the two visual pathways. Using a computer to process an image of a simply lit regular solid form, the investigators were able to analyse the frequency components in an image and then weight them according to two given frequency responses, in order to provide a measure of the stimulation in the two visual pathways. In this experiment a corrugated wave object was used. It was lit horizontally to avoid any specially apprehensive psychological effect. The data were then used to assess the importance of different spatial frequencies in the perception of apparent depth in the image of the solid form. Apparent depths of the image were estimated by comparing with a real object.

“…In the 1960s and 1970s, the concept of light flow was proposed to describe the subjective assessments of the strength and direction of lighting and the potential of light in producing distinct illumination patterns, either at a point or within a light field. [3][4][5][6] Since then, various threedimensional illuminance metrics have been proposed for quantification purposes, including mean cylindrical and semi-cylindrical illuminance, [7][8][9] scalar illuminance (spherical illuminance), 3,10 vectorial illuminance, 11,12 vector-to-scalar illuminance ratio, 4 cylindrical-to-horizontal illuminance ratio, 13 vector-to-cylindrical illuminance ratio 14 and so on. [15][16][17] However, the lack of commercial three-dimensional illuminance metres has limited the interest of lighting designers in vector illuminance-based metrics.…”

Section: Introductionmentioning

confidence: 99%

Determining scalar illuminance from cubic illuminance data. Part 1: Error tracing

Liao

Xiao

Liu

et al. 2022

The cubic illumination metre has been taken as the most thorough and practical tool for the field measurement of vector illuminance so far. However, uncertainty in the measurement of scalar illuminance has influenced its reliability. This study determined how the errors of the existing approaches were generated using illustrations and simulations based on the illuminance solid concept. Following the error analysis of the existing approaches, potential alternative solutions for improving its accuracy were proposed. This study can help pave the way for developing more accurate vector illuminance-based metrics in natural lighting environments using a cubic metre.