| 摘要 |
PURPOSE:To easily express a shadow projected on a different building not to mention the shadow projected on ground (horizontal plane) by projecting the shadow of a first plane on a second plane and clipping an unrequired part within the shadow projected on the second plane. CONSTITUTION:The shadow of the plane-1 is projected on the plane-3 as in a figure. That is, the coordinate of a shadow polygon 3 is found from points where straight lines connecting a light source P and the respective vertexes of the plane-1 cross a plane for which the plane-3 is expanded including the plane-3. That is, the shadow polygon 3 is the shadow of a range shown by (o)-(r). Since the shadow outside the range surrounded by the points (j), (k), (m) and (n) constituting the plane of the building B2 is not actually projected on the plane-3, an arithmetic unit leaves out only the range encircled by the (j), (k), (m) and (n) within the shadow 3 and clips the shadow polygon 3 of the other range. Thus, the shadow polygon 2 of the range surrounded by (c), (e), (f) and (d) is displayed at a display device 5 on the plane-2 and only the shadow polygon 3 of the range shown by the (j), (k), (m) and (n) is displayed on the plane-3. |
