PhotoPlus X2 User Guide - Serif

Using depth maps
Layers and Masks 145
Depth maps let you add remarkable 3D realism to ordinary images. A standard
"flat" image, of course, has only two dimensions: X and Y, or width and height.
Adding a depth map to a layer gives you an extra channel that stores information
for a third (Z-axis or depth) dimension, in effect adding "volume" to the image. It's
as if the original image acquires a surface with peaks and valleys—and you can play
with the elevation of the landscape to achieve different visual results.
The depth map itself is a greyscale representation that uses lightness values to
encode the Z-axis or "elevation" data, with 256 possible levels for each underlying
image pixel. Lighter areas represent peaks and darker areas represent valleys.
Here's a schematic view of how an imaginary 3D volume (the stack on the left)
might be encoded as a depth map:
The several levels of elevation on the stack translate or “map” directly to lightness
values in the greyscale depth map on the right. What PhotoPlus can do is to take
the depth map and translate it back into light-and-shadow information that
appears (to us) as depth in an image... hence the illusion of three-dimensionality.
Typically, you'll begin by creating a new blank depth map on a layer, then modify it
by painting or erasing directly on the map. The varying lightness on the depth map
produces interesting depressions and ridges on the image, which are exposed by
layer effects automatically applied from the 3D Effects category. Changes on the
greyscale map layer produce the effect of highs and lows in the "surface"... it's like
using a 3D brush!