A Modified Phong-Blinn Light Model for Shadowed Areas

The human visual system makes use of the information that shadows provide in order to determine the location of objects. In computer graphics rendered scenes, it can sometimes be difficult to determine whether an object is floating in the air or is placed on the ground. There are two types of shadows. One occurs when an object occludes another object so that light cannot reach it. Instead of using ambient light, as the Phong-Blinn model suggests, for these shadows, the light intensity is decreased making an impression of a shadow. This will prevent the shadow from appearing flat, as it would if only ambient light where used. The other type of shadow, is visible on all polygons facing away from the light source and are therefore not lit. Usually, ambient light only is used for these shadows. We propose an improvement to the Phong-Blinn model, which will make these shadowed polygons more realistic and not appear so flat. This will especially improve the visual appearance of bump mapped objects where the bumps will be visible also on the back-faces