Lighting algorithms for outdoor scenes suffer from the sheer geometric and lighting complexity of such environments. In this paper we introduce an efficient, hierarchical solution to the problem of outdoor illumination. Data structures and sampling algorithms are presented, permitting the integration of complex and natural objects in a hierarchical radiosity simulation system. This new approach...

UNLABELLED Many insects exploit skylight polarization as a compass cue for orientation and navigation. In the fruit fly, Drosophila melanogaster, photoreceptors R7 and R8 in the dorsal rim area (DRA) of the compound eye are specialized to detect the electric vector (e-vector) of linearly polarized light. These photoreceptors are arranged in stacked pairs with identical fields of view and spectr...

One of the main architectural characteristics in the central area of Iran is the relation between life and climatic conditions; e.g., the four-seasonal house which is a typical kind of the central-yard house. As the climate of Isfahan is more pleasant than other desert regions in the central part of Iran, wind towers are replaced with skylights to ventilate the pool area of hoze-khane. So far, ...

Sunlight and skylight are rarely rendered correctly in computer graphics. A major reason for this is high computational expense. Another is that precise atmospheric data is rarely available. We present an inexpensive analytic model that approximates full spectrum daylight for various atmospheric conditions. These conditions are parameterized using terms that users can either measure or estimate...

The variation of the directional reflectance of a vegetative canopy with azimuthal view angle becomes prominent when the canopy is illuminated by the sun at large angles from zenith. An extension of a previous directional reflectance model of vegetative canopies is presented to quantify this effect. The results indicate that the cause of the azimuthal variation can be traced to solar flux illum...

For improved multispectral classification and retrieval of Lambertian reflectances from patches of arbitrary surface orientation, we investigate the consequences of a dichromatic illumination model accounting for direct sunlight and diffuse skylight. This illumination model leads to the concept of spectral classes as two dimensional planes in the feature space. This paper addresses three questi...

High-spectral resolution polarisation measurements of the clear daylight sky reveal an unexpected rich spectral fine-structure in the polarisation superimposed on the more familiar broad-band continuum. This polarisation spectrum shows the spectral fingerprints of scattering and absorption processes which is illustrated with radiative transfer calculations. In particular, radiative transfer cal...

Linear polarization of the clear daytime sky has often been measured as a spectrally integrated or quasi-monochromatic variable, but seldom as a spectral one. So we use a hyperspectral imaging system to measure skylight polarization at high spectral and angular resolutions for clear and hazy skies at our coastal site. The resulting polarization maps and spectra exhibit both commonalities and di...