--- ray/doc/man/man1/rpict.1	2005/01/18 00:33:15	1.4
+++ ray/doc/man/man1/rpict.1	2005/05/31 18:01:08	1.8
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rpict.1,v 1.4 2005/01/18 00:33:15 greg Exp $"
+.\" RCSid "$Id: rpict.1,v 1.8 2005/05/31 18:01:08 greg Exp $"
 .TH RPICT 1 2/26/99 RADIANCE
 .SH NAME
 rpict - generate a RADIANCE picture
@@ -89,6 +89,9 @@ center of a parallel projection.
 .BI -vd " xd yd zd"
 Set the view direction vector to
 .I "xd yd zd".
+The length of this vector indicates the focal distance as needed by the
+.I \-pd
+option, described below.
 .TP
 .BI -vu " xd yd zd"
 Set the view up vector (vertical direction) to
@@ -469,23 +472,23 @@ header of the ambient file.
 .I Getinfo(1)
 may be used to print out this information.
 .TP
-.BI -ae \ mat
+.BI -ae \ mod
 Append
-.I mat
+.I mod
 to the ambient exclude list,
 so that it will not be considered during the indirect calculation.
 This is a hack for speeding the indirect computation by
 ignoring certain objects.
 Any object having
-.I mat
+.I mod
 as its modifier will get the default ambient
 level rather than a calculated value.
-Any number of excluded materials may be given, but each
+Any number of excluded modifiers may be given, but each
 must appear in a separate option.
 .TP
-.BI -ai \ mat
+.BI -ai \ mod
 Add
-.I mat
+.I mod
 to the ambient include list,
 so that it will be considered during the indirect calculation.
 The program can use either an include list or an exclude
@@ -494,16 +497,16 @@ list, but not both.
 .BI -aE \ file
 Same as
 .I \-ae,
-except read materials to be excluded from
+except read modifiers to be excluded from
 .I file.
 The RAYPATH environment variable determines which directories are
 searched for this file.
-The material names are separated by white space in the file.
+The modifier names are separated by white space in the file.
 .TP
 .BI -aI \ file
 Same as
 .I \-ai,
-except read materials to be included from
+except read modifiers to be included from
 .I file.
 .TP
 .BI -me " rext gext bext"
@@ -555,13 +558,29 @@ option (above) may be used to override this.
 .BI -lr \ N
 Limit reflections to a maximum of
 .I N.
+If
+.I N
+is zero, then Russian roulette is used for ray
+termination, and the
+.I -lw
+setting (below) must be positive.
+If N is a negative integer, then this sets the upper limit
+of reflections past which Russian roulette will not be used.
+In scenes with dielectrics and total internal reflection,
+a setting of 0 (no limit) may cause a stack overflow.
 .TP
 .BI -lw \ frac
 Limit the weight of each ray to a minimum of
 .I frac.
-During ray-tracing, a record is kept of the final contribution
-a ray would have to the image.
-If it is less then the specified minimum, the ray is not traced.
+During ray-tracing, a record is kept of the estimated contribution
+(weight) a ray would have in the image.
+If this weight is less than the specified minimum and the
+.I -lr
+setting (above) is positive, the ray is not traced.
+Otherwise, Russian roulette is used to
+continue rays with a probability equal to the ray weight
+divided by the given
+.I frac.
 .TP
 .BI -S \ seqstart
 Instead of generating a single picture based only on the view
@@ -769,7 +788,7 @@ rpict -S 1 -o frame%02d.pic scene.oct < keyframes.vf
 .SH ENVIRONMENT
 RAYPATH		the directories to check for auxiliary files.
 .SH FILES
-/usr/tmp/rtXXXXXX		common header information for picture sequence
+/tmp/rtXXXXXX		common header information for picture sequence
 .br
 rfXXXXXX		temporary name for recover file
 .SH DIAGNOSTICS