--- ray/doc/man/man1/rcontrib.1	2018/01/26 18:11:50	1.14
+++ ray/doc/man/man1/rcontrib.1	2020/09/10 17:52:46	1.19
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rcontrib.1,v 1.14 2018/01/26 18:11:50 rschregle Exp $"
+.\" RCSid "$Id: rcontrib.1,v 1.19 2020/09/10 17:52:46 greg Exp $"
 .TH RCONTRIB 1 5/25/05 RADIANCE
 .SH NAME
 rcontrib - compute contribution coefficients in a RADIANCE scene
@@ -9,6 +9,8 @@ rcontrib - compute contribution coefficients in a RADI
 ][
 .B \-V
 ][
+.B "\-t secs"
+][
 .B "\-c count"
 ][
 .B \-fo
@@ -119,6 +121,26 @@ Note that output flushing via zero-direction rays is d
 .I \-c
 set to zero.
 .PP
+Output flushing at fixed intervals may be enabled with the
+.I \-x
+option, which specifies the number of records
+(-c accumulations) before each flush.
+If the
+.I \-y
+option is also set, then periodic flushing is disabled and the
+output size for an RGB image is the taken from the x and y dimensions.
+In lieu of periodic flushing, a flush may be forced as mentioned above
+by sending a sample with a zero direction vector, although you
+must still send a full record of rays before output occurs.
+.PP
+If progress reports are desired, the
+.I \-t
+option specifies a time interval in seconds for reports sent to
+standard error.
+This requires that the number of input samples is known, meaning a
+.I \-y
+parameter has been specified.
+.PP
 The output of
 .I rcontrib
 has many potential uses.
@@ -211,7 +233,7 @@ Additional parameter values that apply only to this mo
 with a
 .I \-p
 option, which contains a list of variable names and assigned values, separated
-by commas or semicolons.
+by commas, colons, or semicolons.
 The computed bin value will be
 rounded to the nearest whole number.
 (Negative bin values will be silently ignored.)\0
@@ -287,7 +309,9 @@ supports light source contributions from photon maps g
 .I mkpmap(1)
 with its
 .I -apC
-option. In photon mapping mode,
+option. Enabling photon mapping is described in the
+.I rtrace 
+man page along with its relevant settings. In photon mapping mode,
 .I rcontrib
 only supports contributions from light sources, not arbitrary modifiers.
 The
@@ -297,7 +321,7 @@ discussed above. Ray coefficients are also supported v
 .I \-V-
 option. Using fewer photons than there are light sources for the photon
 density estimates results in omitted contributions, thus the bandwidth
-is clamped accordingly and a warning issued.
+is clamped accordingly and a warning is issued. 
 .SH EXAMPLES
 To compute the proportional contributions from sources modified
 by "light1" vs. "light2" on a set of illuminance values:
@@ -328,6 +352,11 @@ rcontrib \-I+ \-h \-V \-fo \-o c_%s.dat \-M lights \-a
 scene.oct < test.dat,
 .SH ENVIRONMENT
 RAYPATH		path to search for \-f and \-M files
+.SH BUGS
+We do not currently compute contributions or coefficients properly
+in scenes with participating media.
+A single warning will be issued if a scattering or absorbing medium
+is detected.
 .SH AUTHOR
 Greg Ward
 .SH "SEE ALSO"