--- ray/src/util/trad.hlp	1995/09/28 14:11:45	2.15
+++ ray/src/util/trad.hlp	1996/05/17 14:59:20	2.17
@@ -1,4 +1,4 @@
-	$Id: trad.hlp,v 2.15 1995/09/28 14:11:45 greg Exp $
+	$Id: trad.hlp,v 2.17 1996/05/17 14:59:20 greg Exp $
 
 This help file is associated with the trad interface to the Radiance
 rad(1) program.  Trad consists of trad.wsh and one do_*.tcl file for
@@ -398,11 +398,26 @@ long as the overall size of the given box is close to 
 size of the space.
 
 The Zone entry windows may be manipulated in the following ways.
-Control-U clears the current window.
 Control-V pastes the contents of the current selection at the
 insertion point.
 Return moves the focus to the next window in the chain.
 
+The "Auto" button may be used to set these values based on the bounding
+box of one or more Radiance scene files.
+
+.Zone.Auto
+
+Use this button to automatically determine the bounding box for this
+zone, based on the output of the "getbbox" command run on one or
+more Radiance scene files.
+The appropriate scene files are entered via a file
+selection dialogue box, which comes up after the button is pressed.
+
+The reason for selecting specific files rather than running getbbox
+on the entire scene is that a zone usually does not include large
+external objects, which may be present in the complete scene
+description.
+
 .Zone.Detail
 
 The "Detail" setting indicates the relative level
@@ -490,7 +505,7 @@ tot_flux is given in watts.
 (Divide total lumens by 179 lumens/watt to get watts.)
 
 The exposure value may either be given as a positive real value, or
-as a real value preceeded by a '+' or '-' indicating a positive or
+as a real value preceded by a '+' or '-' indicating a positive or
 negative number of f-stops (powers of two) from the original value.
 
 If no exposure is given, pfilt will automatically compute the
@@ -682,9 +697,6 @@ The "Clear" button simply clears the "Name" and "Optio
 for the convenience of entering a new view.
 It has no effect on the rad input variables.
 
-Note that Control-U will always clear an entry box whose cursor is
-active.
-
 .Views.Default
 
 The "Set Default" button may be used to make the selected view the
@@ -707,7 +719,7 @@ The standard view up vector may be set to the positive
 the positive Y axis (+Y), the positive Z axis (+Z), the negative
 X axis (-X), the negative Y axis (-Y), or the negative Z axis (-Z).
 
-This setting may always be overriden by the "-vu xd yd zd" option,
+This setting may always be overridden by the "-vu xd yd zd" option,
 and will be altered for a particular view if it happens to be
 parallel to the view direction.