-The \fIdistort\fP program lets circular zones of distortion wander
-randomly around its window, apparently distorting what is under them
-due to the window's pseudo-transparency. The mode of distortion and
-the overall behaviour of the zones can be influenced in various ways.
+The \fIdistort\fP program takes an image and lets circular zones of
+distortion wander randomly around it, distorting what is under them.
+The mode of distortion and the overall behaviour of the zones can be
+influenced in various ways.
+
+The image that it manipulates will be grabbed from the portion of
+the screen underlying the window, or from the system's video input,
+or from a random file on disk, as indicated by
+the \fIgrabDesktopImages\fP, \fIgrabVideoFrames\fP,
+and \fIchooseRandomImages\fP options in the \fI~/.xscreensaver\fP
+file; see
+.BR xscreensaver-demo (1)
+for more details.