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Item Modeling of Skylight and Rendering of Outdoor Scenes(Blackwell Science Ltd and the Eurographics Association, 1993) Tadamura, Katsumi; Nakamae, Eihachiro; Kaneda, Kazufumi; Baba, Masashi; Yamashita, Hideo and Nishita, TomoyukiPhotorealistic animated images are extremely effective for pre-evaluating visual impact of city renewal and construction of tall buildings. In order to generate a photorealistic image not only the direct sunlight but also skylight must be considered.This paper proposes a method of high-fidelity image generation for photorealistic outdoor scenes based on the following ideas: * 1The intensity distribution of skylight taking account of scattering and absorption due to particles in the atmosphere which coincides with CIE standard skylight luminance functions is sought, and realistic images considering about spectrum distribution of skylight for any altitude of the sun can be easily and accurately displayed. * 2A rectangular parallelepiped with a specialized distribution of intensity simulating the skylight is introduced for efficient calculation of illumination due to skylight, and by employing a graphics hardware calculation of the skylight illuminance taking into account shadow effects is obtained with high efficiency- these techniques can be used to generate sequences of images, making animations possible at far lower calculation cost than previous methods.Item A New Radiosity Approach Using Area Sampling for Parametric Patches(Blackwell Science Ltd and the Eurographics Association, 1993) Nishita, Tomoyuki; Nakamae, EihachiroA high precision illumination model is indispensable for lighting simulation and realistic image synthesis. For the purpose of improving realism, research on global illumination has been done, and several papers on radiosity methods have been presented. In the most recently proposed methods, the shapes of light sources and objects are restricted to polygons or simple curved surfaces. We present a more general method which can handle the kind of free-form surfaces widely used in industrial products and in architecture. The method proposed here solves the problem of the interreflection of light (i.e., radiosities) between patches, and form-factors, which play an important role in this process, are precisely calculated without aliasing through the use of an area sampling method (i.e., pyramid tracing). Furthermore the method can handle both non-uniform intensity curved sources and non-diffuse surfaces.