Note: this page describes v1.6, and does not yet include v2 features.
The Depth window creates depth from the colors of a picture, to either create a new depth map or add to the existing one. This allows lighting effects to be applied to imported pictures, and bump map effects on rendered objects. You can also bring in flat or textured backgrounds and allow a rendered object to cast shadows onto the background.
Here is a photo with five examples of lighting using the same depth settings.