A methodology for generating a drop shadow effect for objects in a
graphical user interface is presented. A first object in a presentation
space occludes the illumination from a simulated light source, and a
dynamically determined drop shadow from the first object may partially
occlude a second object. A portion of a drop shadow from the first object
is shown on the second object; the portion of the drop shadow from the
first object is displaced from the first object in direct proportion to a
z-depth difference between the first object and the second object. Hence,
a drop shadow can be generated in a computationally inexpensive manner,
and the dynamically determined drop shadow enhances the perception of
depth within the presentation space by a user.