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This paper examines rendering techniques of outdoor scenes intended for use in visual environmental assessment using computer graphics and/or video sequence images and discusses their advantages and limitations. The techniques are classified into the following three categories. First, rendering techniques of computer generated images and montages creating a photo-realistic landscape image based on optical phenomena are introduced; these are quite useful for careful and detailed study of landscapes. Second, a method for creating a precise panoramic image from panned video sequence images taken on a tripod is introduced; this is very useful for evaluating the whole visual landscape. Third, technique examined is panned/zoomed landscape video sequence images well matched with photo realistic computer generated still images such as bridges and electric power transmission towers; this provides an especially vivid and lifelike impression.

Water surface is an important element for rendering a realistic landscape image, particularly for visual environmental assessment. The incident light from the water surface to the viewpoint generally consists of two components, reflected and refracted light. The source of the latter is further subdivided into reflected light from the bottom of the water and scattered light in it. In order to render a realistic water surface, the calculation for each component of the light is a quite complex and time consuming task. We propose the fast rendering algorithms of the water surface for visual environmental assessment of outdoor scenes. The features are: (1) the reflected light from the water surface is rendered very quickly through the quasi-ray tracing techniques, which employ inversion and reflection mapping with consideration of the depth of objects mirrored on the water surface; (2) the refracted light coming through the water surface, which gives the color of water, is efficiently calculated by using a look-up table in which both characteristics of the light sources (both direct sunlight and skylight) and the effects of scattering and attenuation depending on turbidity are taken into account. In order to testify the proposed algorithms, some examples are given.