Abstract
In lighting design, shadows are one of the important elements to be considered. This paper proposes a method of illuminance calculation in consideration of shadows caused by several objects (approximated by convex polyhedra) and flat surface sources having arbitrary shapes (approximated by convex polygons). This paper also discusses the depiction method of the calculated illuminance by using the perspective viewed from an arbitrary position.
The advanced points of this paper are as follows:
(1) Obtaining volumes of penumbrae and umbrae, and calculating the shadow boundaries on each illuminated face prior to illuminance calculation, shorten the computation time.(2) Applying to contour integration method for the visible segments of the source's boundary when viewed from the calculating point and for the visible segments of the contour line of polyhedra simplify the calculation of the illuminance in the penumbrae caused by several polyhedra.(3) Even though the shape of the light source is basically treated as a convex polygon, using the hypothetical sources or the cover face beneath the source makes it possible to deal with a concave polygon source (including holes).(4) The illuminance values are displayed on the perspective image viewed from an arbitrary position, then even laymen can discuss the psychological effects and can easily grasp the distribution of illuminance.
