--- ray/doc/man/man1/rtcontrib.1	2005/10/06 05:49:44	1.12
+++ ray/doc/man/man1/rtcontrib.1	2009/06/14 18:21:58	1.22
@@ -1,4 +1,4 @@
-.\" RCSid "$Id: rtcontrib.1,v 1.12 2005/10/06 05:49:44 greg Exp $"
+.\" RCSid "$Id: rtcontrib.1,v 1.22 2009/06/14 18:21:58 greg Exp $"
 .TH RTCONTRIB 1 5/25/05 RADIANCE
 .SH NAME
 rtcontrib - compute contribution coefficients in a RADIANCE scene
@@ -7,6 +7,12 @@ rtcontrib - compute contribution coefficients in a RAD
 [
 .B "\-n nprocs"
 ][
+.B \-V
+][
+.B "\-c count"
+][
+.B \-fo
+|
 .B \-r
 ][
 .B "\-e expr"
@@ -37,7 +43,7 @@ rtrace options
 .B "rtcontrib [ options ] \-defaults"
 .SH DESCRIPTION
 .I Rtcontrib
-computes ray contributions (i.e., color coefficients)
+computes ray coefficients
 for objects whose modifiers are named in one or more
 .I \-m
 settings.
@@ -52,6 +58,65 @@ this file.
 (No search takes place if a file name begins with a '.', '/' or '~'
 character.)\0
 .PP
+If the
+.I \-n
+option is specified with a value greater than 1, multiple
+.I rtrace
+processes will be used to accelerate computation on a shared
+memory machine.
+Note that there is no benefit to using more processes
+than there are local CPUs available to do the work, and the
+.I rtcontrib
+process itself may use a considerable amount of CPU time.
+.PP
+By setting the boolean
+.I \-V
+option, you may instruct
+.I rtcontrib
+to report the contribution from each material rather than the ray
+coefficient.
+This is particularly useful for light sources with directional output
+distributions, whose value would otherwise be lost in the shuffle.
+With the default
+.I -V-
+setting, the output of rtcontrib is a coefficient that must be multiplied
+by the radiance of each material to arrive at a final contribution.
+This is more convenient for computing daylight coefficeints, or cases
+where the actual radiance is not desired.
+Use the
+.I -V+
+setting when you wish to simply sum together contributions
+(with possible adjustment factors) to obtain a final radiance value.
+Combined with the
+.I \-i
+or
+.I \-I
+option, irradiance contributions are reported by
+.I \-V+
+rather than radiance, and 
+.I \-V-
+coefficients contain an additonal factor of PI.
+.PP
+The
+.I \-c
+option tells
+.I rtcontrib
+how many rays to accumulate for each record.
+The default value is 1, meaning a full record will be produced for
+each input ray.
+For values greater than 1, contributions will be averaged together
+over the given number of input rays.
+If set to zero, only a single record will be produced at the very
+end, corresponding to the sum of all rays given on the input
+(rather than the average).
+This is equivalent to passing all the output records through a program like
+.I total(1)
+to sum RGB values together, but is much more efficient.
+Using this option, it is possible to reverse sampling, sending rays from
+a parallel source such as the sun to a diffuse surface, for example.
+Note that output flushing via zero-direction rays is disabled
+for accumulated evaluations.
+.PP
 The output of
 .I rtcontrib
 has many potential uses.
@@ -66,7 +131,7 @@ systems, such as luminaires, light pipes, and shading 
 .I Rtcontrib
 calls
 .I rtrace(1)
-with the -oTW option to calculate the daughter ray
+with the \-oTW (or \-oTV) option to calculate the daughter ray
 contributions for each input ray, and the output tallies
 are sent to one or more destinations according to the given
 .I \-o
@@ -74,9 +139,19 @@ specification.
 If a destination begins with an exclamation mark ('!'), then
 a pipe is opened to a command and data is sent to its standard input.
 Otherwise, the destination is treated as a file.
-An existing file of the same name is clobbered, unless the
+An existing file of the same name will not be clobbered, unless the
+.I \-fo
+option is given.
+If instead the
 .I \-r
-option is specified, in which case data recovery is attempted.
+option is specified, data recovery is attempted on existing files.
+(If 
+.I "\-c 0"
+is used together with the
+.I \-r
+option, existing files are read in and new ray evaluations are added
+to the previous results, providing a convenient means for
+progressive simulation.)\0
 If an output specification contains a "%s" format, this will be
 replaced by the modifier name.
 The
@@ -89,8 +164,17 @@ The actual bin number is computed at run time based on
 and surface intersection, as described below.
 If the number of bins is known in advance, it should be specified with the
 .I \-bn
-option, especially for output files containing multiple bins.
-Set this to 0 if the number of bins is unknown (the default).
+option, and this is critical for output files containing multiple values
+per record.
+A variable or constant name may be given for this parameter if
+it has been defined via a previous
+.I \-f
+or
+.I \-e
+option.
+Since bin numbers start from 0, the bin count is always equal to
+the last bin plus 1.
+Set the this value to 0 if the bin count is unknown (the default).
 The most recent
 .I \-b,
 .I \-bn
@@ -98,8 +182,15 @@ and
 .I \-o
 options to the left of each
 .I \-m
-setting affect only that modifier.
-(The ordering of other options is unimportant.)\0
+setting are the ones used for that modifier.
+The ordering of other options is unimportant, except for
+.I \-x
+and
+.I \-y
+if the
+.I \-c
+is 0, when they control the resolution string
+produced in the corresponding output.
 .PP
 If a
 .I \-b
@@ -174,17 +265,6 @@ suitable for manipulation with
 .I pcomb(1)
 and related tools.
 .PP
-If the
-.I \-n
-option is specified with a value greater than 1, multiple
-.I rtrace
-processes will be used to accelerate computation on a shared
-memory machine.
-Note that there is no benefit to using more processes
-than there are local CPUs available to do the work, and the
-.I rtcontrib
-process itself may use a considerable amount of CPU time.
-.PP
 Options may be given on the command line and/or read from the
 environment and/or read from a file.
 A command argument beginning with a dollar sign ('$') is immediately
@@ -195,28 +275,28 @@ replaced by the contents of the given file.
 To compute the proportional contributions from sources modified
 by "light1" vs. "light2" on a set of illuminance values:
 .IP "" .2i
-rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
+rtcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
 .PP
 To generate a pair of images corresponding to these two lights'
 contributions:
 .IP "" .2i
-vwrays -ff -x 1024 -y 1024 -vf best.vf |
-rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
-@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
+vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf |
+rtcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf`
+@render.opt \-o c_%s.hdr \-m light1 \-m light2 scene.oct
 .PP
 These images may then be recombined using the desired outputs
 of light1 and light2:
 .IP "" .2i
-pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
+pcomb \-c 100 90 75 c_light1.hdr \-c 50 55 57 c_light2.hdr > combined.hdr
 .PP
 To compute an array of illuminance contributions according to a Tregenza sky:
 .IP "" .2i
-rtcontrib -I+ -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
-@render.opt -f tregenza.cal scene.oct < test.dat
+rtcontrib \-I+ \-b tbin \-o sky.dat \-m skyglow \-b 0 \-o ground.dat \-m groundglow
+@render.opt \-f tregenza.cal scene.oct < test.dat
 .SH ENVIRONMENT
-RAYPATH		path to search for -f and -M files
+RAYPATH		path to search for \-f and \-M files
 .SH AUTHOR
 Greg Ward
 .SH "SEE ALSO"
-cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
-rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)
+cnt(1), genklemsamp(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
+rcalc(1), rpict(1), rtrace(1), total(1), vwrays(1), ximage(1)