The simplest of all images formed in geometrical optics is the shadow, which occurs “when an opaque object in the path of a light source prevents the light source from traveling through to the surface behind the object.”1 This description may seem simplistic, but it establishes the key relationships that exist between architecture, light, and object. It is quite common to see studies done in environmental plugins such as Ladybug for Grasshopper that depict light in terms of absolute light and absolute shadow (umbra). Though architects are commonly interested in the white, daylit portions of these studies, this archetype encourages architects to instead consider the movement of the shadow image over the course of time and to expand its rigid, black outlines to include the consideration of the softer, layered penumbras that are an integral part of our observation of objects in space.
The role of architecture in forming the shadow primarily lies in framing natural light as it enters a space and interacts with the objects within it. It acts as a filter through which the single, distant, and highly directional light of the sun can be instantaneously operated upon and controls the number, size, and proportion of the sources of natural light that illuminate the interior. Though the directionality of the light is dependent upon the time of year and amount of light scattering (2) that has already occurred due to weather, the points from which light enters a room can have a significant impact upon the appearance of the shadow image.
In a way, the shadow inscribes the presence of the architecture on its own interior skin, and never fails to record the passage of time until artificial light sources control the image instead.
All obstacles, furniture, louver, or screen, are subject to produce shadows of variable size and definition. Architecture determines, to a certain degree, what the nature of the produced image will be. For example, based on the sources of light produced by the architecture, the image can be fragmented, smoothly gradated, or nonexistent. These conditions can be altered by increasing the number of small sources, changing the proportion of the light source, or changing the distance between the source, object, and nearest surface. In the event that a screen is placed directly in front of the source, the image of that entity will appear to be projected onto the objects of the room – depending on the directionality of the source, its image may be preserved or, on a diffuse day, it may only affect those surfaces that it is closest to. The shadow is useful in exposing to us the agency of architecture in framing the light of the sun.
1. Galen Duree Jr., Optics for Dummies (Indianapolis: Wiley, 2011), 60. Galen Duree is a professor of physics and Optical Engineering Director at the Centre for Applied Optics Studies Rose-Hulman Institute of Technology.
2. Ibid., 48.