--- ray/doc/man/man1/gendaymtx.1	2014/06/17 18:03:48	1.7
+++ ray/doc/man/man1/gendaymtx.1	2019/05/28 15:19:17	1.9
@@ -1,4 +1,4 @@
-.\" RCSid $Id: gendaymtx.1,v 1.7 2014/06/17 18:03:48 greg Exp $
+.\" RCSid $Id: gendaymtx.1,v 1.9 2019/05/28 15:19:17 greg Exp $
 .TH GENDAYMTX 1 01/19/13 RADIANCE
 .SH NAME
 gendaymtx - generate an annual Perez sky matrix from a weather tape
@@ -67,10 +67,16 @@ corresponding to a 20% gray.
 .PP
 The
 .I \-d
-option may be used to produce a sun-only matrix, with no sky contributions.
+option may be used to produce a sun-only matrix, with no sky contributions,
+and the ground patch also set to zero.
 Alternatively, the
 .I \-s
-option may be used to exclude any direct solar component from the output.
+option may be used to exclude any direct solar component from the output,
+with the rest of the sky and ground patch unaffected.
+If there is a sun in the description,
+.I gendaymtx
+will include its contribution in the four nearest sky patches,
+distributing energy according to centroid proximity.
 .PP
 By default,
 .I gendaymtx