Abstract

Rendering Terrain with Shadow Lines in ArcGIS
Track: Cartography and Map Production
Authors: Patrick Kennelly

Shadows are an important visual cue in three dimensional (3D) renderings. In ArcGIS, the user can easily add shadows to hillshadings of terrain, but generally these shadows do little more than overprint areas of dark hillshading. The technique described in this presentation uses shadows alone to create a 3D rendering of terrain. The methodology first defines areas of shadows for various azimuths and relatively low inclinations of illumination. Next, it converts these shadowed grids to polygons and applies a hatching area fill to each polygon that is parallel to the illumination vector. Hatching lines become thicker for areas that remain in shadow at greater inclinations of illumination. Because hatching lines are oriented parallel to different azimuths of illumination, the overall effect is similar to the artistic technique of cross hatching. The resulting rendering creates a 3D effect without hillshading the terrain, offering a stylized alternative method of cartographic relief representation.