--- ray/doc/man/man1/pvsum.1	2025/03/27 01:26:55	1.1
+++ ray/doc/man/man1/pvsum.1	2025/05/22 21:39:42	1.4
@@ -1,4 +1,4 @@
-.\" RCSid $Id: pvsum.1,v 1.1 2025/03/27 01:26:55 greg Exp $"
+.\" RCSid $Id: pvsum.1,v 1.4 2025/05/22 21:39:42 greg Exp $"
 .TH PVSUM 1 12/09/09 RADIANCE
 .SH NAME
 pvsum - sum component Radiance pictures based on vector or matrix
@@ -64,8 +64,8 @@ option is given, all data is sent to the standard outp
 which may be a sequence of Radiance pictures as understood by
 .I ra_rgbe(1)
 in the case of a multi-column input matrix.
-(Note that there is currently no Radiance tool that understands a
-concatenated series of float or spectral pictures.)\0
+(Note that there is currently no Radiance tool that fully
+handles a concatenated series of float or spectral pictures.)\0
 .PP
 The
 .I \-N
@@ -85,39 +85,30 @@ gensky 6 21 12 | genskyvec | rmtxop Blinds30.xml
 Window2.dmx - | pvsum view%03d.hdr > view_6-21-12.hdr
 .PP
 To compute a set of hourly spectral pictures at SFO airport
-from a weather tape and set of Tregenza component pictures:
+from a weather tape and set of Tregenza component pictures using
+10 processes:
 .IP "" .2i
-gensdaymtx sfo.epw | pvsum -o timestep%04d.hsr tregcomp%03d.hsr
+gensdaymtx -of sfo.epw | pvsum -o timestep%04d.hsr -N 10 tregcomp%03d.hsr
 .SH NOTES
-This tool is annoyingly similar to
+This tool overlaps with
 .I dctimestep,
-but provides some important capabilities.
-First,
+but provides some missing capabilities.
+Foremost,
 .I pvsum
 reads and can produce spectral pictures and matrices, whereas
 .I dctimestep
 expects and requires 3-component pictures and matrices throughout.
-Changing the data structures in
-.I dctimestep
-proved too difficult and likely to
-lead to a less efficient implementation, especially on systems with
-limited memory.
-In contrast,
+In addition,
 .I pvsum
 accelerates picture sums on Unix systems with more
-memory and processint ability.
-Second, operation was simplified by focusing on the Daylight Coefficient
+memory and CPU cores.
+Operations were simplified by focusing on the Daylight Coefficient
 command form, where the DC matrix is represented as a collection of
 pictures.
-By excluding the three or four other operation modes of
-.I dctimestep,
-new features could be explored in
-.I pvsum.
-For example, 
+Finally,
 .I pvsum
-can write picture data to a series of commands, which
-.I dctimestep
-does not support.
+offers more flexible floating-point support and
+can output to commands as well as files.
 .SH AUTHOR
 Greg Ward
 .SH "SEE ALSO"