--- ray/doc/man/man1/rtpict.1	2019/07/23 18:17:54	1.3
+++ ray/doc/man/man1/rtpict.1	2022/04/10 03:46:27	1.10
@@ -1,7 +1,7 @@
-.\" RCSid "$Id: rtpict.1,v 1.3 2019/07/23 18:17:54 greg Exp $"
+.\" RCSid "$Id: rtpict.1,v 1.10 2022/04/10 03:46:27 greg Exp $"
 .TH RTPICT 1 3/19/2018 RADIANCE
 .SH NAME
-rtpict - generate a RADIANCE picture or layerd image using rtrace
+rtpict - generate a RADIANCE picture or layered image using rtrace
 .SH SYNOPSIS
 .B rtpict
 .B "-n nproc"
@@ -62,12 +62,12 @@ in the specified directory:
 .sp
 .nf
 v	radiance.hdr
-r	mirrored.hdr
-x	unmirrored.hdr
-l	effective.dpt
-L	firstsurface.dpt
-R	mirrored.dpt
-X	unmirrored.dpt
+r	r_refl.hdr
+x	r_unrefl.hdr
+l	d_effective.dpt
+L	d_firstsurf.dpt
+R	d_refl.dpt
+X	d_unrefl.dpt
 n	perturbed.nrm
 N	unperturbed.nrm
 s	surface.idx
@@ -84,7 +84,8 @@ converted to a 16-bit representation by
 .I rcode_depth(1),
 and the
 .I \-d
-option should be used to assign the reference (median) depth and units.
+option should be used to assign the reference (median) depth and world
+units, which applies to the overall scene.
 Surface normals (from the 'n' and 'N' types) will be converted
 to a 32-bit representation by
 .I rcode_normal(1).
@@ -99,7 +100,7 @@ with the 'v' type will be renamed
 .I "irradiance.hdr"
 and some other output types become irrelevant (i.e., 'r', 'x', 'R', and 'X').
 If one or more of the associated output files already exists in the
-destination directory, it will be overwritten with the new data.
+destination directory, an error will be printed and the command will abort.
 .SH EXAMPLES
 To render a scene with four processes:
 .IP "" .2i
@@ -108,9 +109,29 @@ rtpict -n 4 -vf mypers.vf -ab 1 -af scene.amb scene.oc
 To render radiance, first surface distance, and normals in a layered image:
 .IP "" .2i
 rtpict -n 8 -vf fish.vf @render.opt -ovLn fisholay scene.oct
+.SH NOTES
+Users should seriously consider using
+.I rpiece(1)
+for multiprocessing
+when irradiance caching is employed with a shared ambient file.
+If
+.I rtpict
+is used with
+.I \-n
+greater than 1, it tries to compute neighboring parts
+of the same scanline in different processes, which can
+result in many redundant calculations and cache entries.
+.I Rtpict
+will automatically run a randomly-ordered overture calculation
+to mitigate this problem, but it is not a perfect solution.
+.I Rpiece
+avoids redundant cache calculations by working on separate tiles in each
+process, which brings other benefits as well, such as enabling the
+.I \-ps
+option for image plane sampling.
 .SH AUTHOR
 Greg Ward
 .SH "SEE ALSO"
 getinfo(1), mkpmap(1), oconv(1), pfilt(1), 
 pvalue(1), rad(1), rcode_depth(1), rcode_normal(1), rcode_ident(1),
-rpiece(1), rpict(1), rsplit(1), rtrace(1), rvu(1), vwrays(1),
+rcrop(1), rpiece(1), rpict(1), rsplit(1), rtrace(1), rvu(1), vwrays(1)