--- ray/doc/man/man1/rcontrib.1	2018/01/26 18:11:50	1.14
+++ ray/doc/man/man1/rcontrib.1	2019/02/22 19:42:27	1.16
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rcontrib.1,v 1.14 2018/01/26 18:11:50 rschregle Exp $"
+.\" RCSid "$Id: rcontrib.1,v 1.16 2019/02/22 19:42:27 greg Exp $"
 .TH RCONTRIB 1 5/25/05 RADIANCE
 .SH NAME
 rcontrib - compute contribution coefficients in a RADIANCE scene
@@ -287,7 +287,9 @@ 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 +299,7 @@ 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 +330,11 @@ 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"