Ultimatte-9 Operations Manual
March 1, 2000
3
6. FG/BG Interaction
In addition to the planning and care required to produce a technically good composite, imagination plays
a role in creating an image that encourages the viewer to believe it is real. Having the FG subject appear
to interact with the BG scene in some way will increase the believability of the composite.
Allowing the FG subject cast a shadow on to the BG is one form of apparent interaction. A set piece in the
FG that matches the background color can be used to cast a shadow conforming to an object in the BG.
A combination of real props and set pieces in the FG can be magical, even to an experienced eye.
Letting the reflection of the FG object appear on a surface in the BG scene is another form of apparent
interaction that can convince a viewer that the image is real. Unlike other systems, an Ultimatte-9 will
composite a reflection just like any other FG object. It is only necessary to add a reflective surface to the
backing. Glossy paint or Plexiglas can be
used to create reflections that will appear to be on marble
floors, shiny metal objects or windows in the final composite.
Finally, the External Matte input on the Ultimatte-9 provides a powerful tool for creating apparent
interaction with the BG, especially if the BG is a computer generated environment or a piece of art. An
External Matte signal conforming to the shape of an object in the BG will override the internally generated
matte signal and force that object to obscure the FG. The External Matte signal can be turned ON and
OFF allowing the FG subject to appear to go both in front of and behind an object in the BG.
