--- ray/doc/man/man1/gendaymtx.1	2019/06/25 00:09:45	1.10
+++ ray/doc/man/man1/gendaymtx.1	2020/04/13 17:12:19	1.12
@@ -1,4 +1,4 @@
-.\" RCSid $Id: gendaymtx.1,v 1.10 2019/06/25 00:09:45 greg Exp $
+.\" RCSid $Id: gendaymtx.1,v 1.12 2020/04/13 17:12:19 greg Exp $
 .TH GENDAYMTX 1 01/19/13 RADIANCE
 .SH NAME
 gendaymtx - generate an annual Perez sky matrix from a weather tape
@@ -11,8 +11,12 @@ gendaymtx - generate an annual Perez sky matrix from a
 ][
 .B "\-A"
 ][
-.B "\-d|\-s"
+.B "\-d|\-s|\-n"
 ][
+.B "\-D sunfile"
+][
+.B "\-M sunmods"
+][
 .B "\-r deg"
 ][
 .B "\-m N"
@@ -44,7 +48,7 @@ parameter setting.
 .PP
 Increasing the
 .I \-m
-parameter, typically by factors of two, yields a higher resolution
+parameter yields a higher resolution
 sky using the Reinhart patch subdivision.
 For example, setting
 .I "\-m 4"
@@ -88,6 +92,37 @@ If there is a sun in the description,
 will include its contribution in the four nearest sky patches,
 distributing energy according to centroid proximity.
 .PP
+The
+.I \-n
+option may be used if no matrix output is desired.
+This may be used to merely check the input, or in combination with the
+.I \-D
+option, below.
+.PP
+The
+.I \-D
+option may be used to specify an output file to contain a list of
+solar positions and intensities corresponding to time steps in the
+weather tape where the sun has any portion above the horizion.
+Sun radiance values may be zero if the direct amount is zero on the input.
+Sun modifiers and names will be indexed by the minute, numbered from
+midnight, January 1st.
+If a hyphen ('-') is given as the argument to
+.I \-D,
+then the sun descriptions  will be directed to the standard output.
+This implies the
+.I \-n
+option just described.
+If the
+.I \-M
+option is given as well, it will be used to record the modifier
+names used in the
+.I \-D
+output, for convenient input to
+.I rcontrib(1)
+and
+.I rfluxmtx(1).
+.PP
 By default,
 .I gendaymtx
 assumes the positive Y-axis points north such that the first sky patch
@@ -144,4 +179,4 @@ based on Jean-Jacques Delaunay's original gendaylit(1)
 Greg Ward wrote the final parameter parsing and weather tape conversion.
 .SH "SEE ALSO"
 dctimestep(1), genBSDF(1), gendaylit(1), gensky(1), genskyvec(1),
-rcollate(1), rcontrib(1), xform(1)
+rcollate(1), rcontrib(1), rfluxmtx(1), xform(1)