Graphics Reference
In-Depth Information
Figure 36.19: (Top) View inside Fred Brooks' bedroom. There are two open doors and
a mirror between them. The resultant portals are outlined in white and the mirrors are
outlined in red. (Bottom) Schematic of visible regions for the observer from the top image.
Note how the sight lines to the mirror give rise to a reflected visibility frustum that passes
behind the viewer. (Courtesy of David Luebke ©1995 ACM, Inc. Reprinted by permission.)
The extension to mirrors is conceptually straightforward. We can model a mir-
ror as a portal to a virtual world that resembles the real world but is flipped left-to-
right. To implement this, augment
portalRender
to track whether the viewpoint
has been reflected through an even or odd number of mirrors, and reflect the viewer
through the plane of the mirror. Two complications of the mirrors are that they
