man/man1/rcontrib.1

.\" RCSid "$Id: rcontrib.1,v 1.17 2020/03/14 16:25:46 greg Exp $"
.TH RCONTRIB 1 5/25/05 RADIANCE
.SH NAME
rcontrib - compute contribution coefficients in a RADIANCE scene
.SH SYNOPSIS
.B rcontrib
[
.B "\-n nprocs"
][
.B \-V
][
.B "\-t secs"
][
.B "\-c count"
][
.B \-fo
|
.B \-r
][
.B "\-e expr"
][
.B "\-f source"
][
.B "\-o ospec"
][
.B "\-p p1=V1,p2=V2"
][
.B "\-b binv"
][
.B "\-bn nbins"
]
{
.B "\-m mod | \-M file"
}
..
[
.B $EVAR
]
[
.B @file
]
[
rtrace options
]
.B octree
.br
.B "rcontrib [ options ] \-defaults"
.SH DESCRIPTION
.I Rcontrib
computes ray coefficients
for objects whose modifiers are named in one or more
.I \-m
settings.
These modifiers are usually materials associated with
light sources or sky domes, and must directly modify some geometric
primitives to be considered in the output.
A modifier list may also be read from a file using the
.I \-M
option.
The RAYPATH environment variable determines directories to search for
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
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 rcontrib
process itself may use a considerable amount of CPU time.
.PP
By setting the boolean
.I \-V
option, you may instruct
.I rcontrib
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 rcontrib 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 rcontrib
how many rays to accumulate for each record.
The default value is one, meaning a full record will be produced for
each input ray.
For values greater than one, 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 with
.I \-c
set to zero.
.PP
If progress reports are desired, the
.I \-t
option specifies a time interval in seconds for reports sent to
standard error.
.PP
The output of
.I rcontrib
has many potential uses.
Source contributions can be used as components in linear combination to
reproduce any desired variation, e.g., simulating lighting controls or
changing sky conditions via daylight coefficients.
More generally,
.I rcontrib
can be used to compute arbitrary input-output relationships in optical
systems, such as luminaires, light pipes, and shading devices.
.PP
.I Rcontrib
sends the accumulated rays tallies
to one or more destinations according to the given
.I \-o
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 will not be clobbered, unless the
.I \-fo
option is given.
If instead the
.I \-r
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
.I \-b
option may be used to further define
a "bin number" within each object if finer resolution is needed, and
this will be applied to a "%d" format in the output file
specification if present. 
(The final integer will be offset incrementally
if the output is a RADIANCE picture and more than one modifier has
the same format specification.)\0
The actual bin number is computed at run time based on ray direction
and surface intersection, as described below.
The number of bins must be specified in advance with the
.I \-bn
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 zero, the bin count is always equal to
the last bin plus one.
The most recent
.I \-p,
.I \-b,
.I \-bn
and
.I \-o
options to the left of each
.I \-m
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 zero, when they control the resolution string
produced in the corresponding output.
.PP
If a
.I \-b
expression is defined for a particular modifier,
the bin number will be evaluated at run time for each
ray contribution.
Specifically, each ray's world intersection point will be assigned to
the variables Px, Py, and Pz, and the normalized ray direction
will be assigned to Dx, Dy, and Dz.
These parameters may be combined with definitions given in
.I \-e
arguments and files read using the
.I \-f
option.
Additional parameter values that apply only to this modifier may be specified
with a
.I \-p
option, which contains a list of variable names and assigned values, separated
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
For a single bin, you may specify
.I "\-b 0",
which is the default.
This mechanism allows the user to define precise regions or directions
they wish to accumulate, such as the Tregenza sky discretization,
which would be otherwise impossible to specify
as a set of RADIANCE primitives.
The rules and predefined functions available for these expressions are
described in the
.I rcalc(1)
man page.
Like
.I rcalc,
.I rcontrib
will search the RADIANCE library directories for each file given in a
.I \-f
option.
.PP
If no
.I \-o
specification is given, results are written on the standard output in order
of modifier (as given on the command line) then bin number.
Concatenated data is also sent to a single destination (i.e., an initial
.I \-o
specification without formatting strings).
If a "%s" format appears but no "%d" in the
.I \-o
specification, then each modifier will have its own output file, with
multiple values per record in the case of a non-zero
.I \-b
definition.
If a "%d" format appears but no "%s", then each bin will get its own
output file, with modifiers output in order in each record.
For text output, each RGB coefficient triple is separated by a tab,
with a newline at the end of each ray record.
For binary output formats, there is no such delimiter to mark
the end of each record.
.PP
Input and output format defaults to plain text, where each ray's
origin and direction (6 real values) are given on input,
and one line is produced per output file per ray.
Alternative data representations may be specified by the
.I \-f[io]
option, which is described in the
.I rtrace
man page along with the associated
.I \-x
and
.I \-y
resolution settings.
In particular, the color ('c') output data representation
together with positive dimensions for
.I \-x
and
.I \-y
will produce an uncompressed RADIANCE picture,
suitable for manipulation with
.I pcomb(1)
and related tools.
.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
replaced by the contents of the given environment variable.
A command argument beginning with an at sign ('@') is immediately
replaced by the contents of the given file.
.PP
.I Rcontrib
supports light source contributions from photon maps generated by
.I mkpmap(1)
with its
.I -apC
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
.I -b
option is supported along with its associated ray variables, as
discussed above. Ray coefficients are also supported via the
.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 is issued. 
.SH EXAMPLES
To compute the proportional contributions from sources modified
by "light1" vs. "light2" on a set of illuminance values:
.IP "" .2i
rcontrib \-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 |
rcontrib \-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.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
rcontrib \-I+ \-f tregenza.cal \-b tbin \-bn Ntbins \-o sky.dat \-m skyglow
\-b 0 \-o ground.dat \-m groundglow @render.opt scene.oct < test.dat
.PP
To perform an annual simulation of 365 daily sun positions in photon mapping
mode:
.IP "" .2i
rcontrib \-I+ \-h \-V \-fo \-o c_%s.dat \-M lights \-ap contrib.pm 365
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"
cnt(1), genklemsamp(1), getinfo(1), mkpmap(1), pcomb(1), pfilt(1), 
ra_rgbe(1), rcalc(1), rfluxmtx(1), rmtxop(1), rpict(1), rsensor(1), 
rtrace(1), total(1), vwrays(1), ximage(1)

Revision:	1.18
Committed:	Wed Sep 9 21:28:19 2020 UTC (5 years, 1 month ago) by greg
Branch:	MAIN
Changes since 1.17:	+8 -1 lines
Log Message:	feat(rcontrib,rfluxmtx): Added -t option to specify progress report interval
#	User	Rev	Content
1	greg	1.18	.\" RCSid "$Id: rcontrib.1,v 1.17 2020/03/14 16:25:46 greg Exp $"
2	greg	1.2	.TH RCONTRIB 1 5/25/05 RADIANCE
3	greg	1.1	.SH NAME
4			rcontrib - compute contribution coefficients in a RADIANCE scene
5			.SH SYNOPSIS
6			.B rcontrib
7			[
8			.B "\-n nprocs"
9			][
10			.B \-V
11			][
12	greg	1.18	.B "\-t secs"
13			][
14	greg	1.1	.B "\-c count"
15			][
16			.B \-fo
17			\|
18			.B \-r
19			][
20			.B "\-e expr"
21			][
22			.B "\-f source"
23			][
24			.B "\-o ospec"
25			][
26	greg	1.10	.B "\-p p1=V1,p2=V2"
27			][
28	greg	1.1	.B "\-b binv"
29			][
30			.B "\-bn nbins"
31			]
32			{
33			.B "\-m mod \| \-M file"
34			}
35			..
36			[
37			.B $EVAR
38			]
39			[
40			.B @file
41			]
42			[
43			rtrace options
44			]
45			.B octree
46			.br
47			.B "rcontrib [ options ] \-defaults"
48			.SH DESCRIPTION
49	greg	1.3	.I Rcontrib
50	greg	1.1	computes ray coefficients
51			for objects whose modifiers are named in one or more
52			.I \-m
53			settings.
54			These modifiers are usually materials associated with
55			light sources or sky domes, and must directly modify some geometric
56			primitives to be considered in the output.
57			A modifier list may also be read from a file using the
58			.I \-M
59			option.
60			The RAYPATH environment variable determines directories to search for
61			this file.
62			(No search takes place if a file name begins with a '.', '/' or '~'
63			character.)\0
64			.PP
65			If the
66			.I \-n
67			option is specified with a value greater than 1, multiple
68			processes will be used to accelerate computation on a shared
69			memory machine.
70			Note that there is no benefit to using more processes
71			than there are local CPUs available to do the work, and the
72			.I rcontrib
73			process itself may use a considerable amount of CPU time.
74			.PP
75			By setting the boolean
76			.I \-V
77			option, you may instruct
78			.I rcontrib
79			to report the contribution from each material rather than the ray
80			coefficient.
81			This is particularly useful for light sources with directional output
82			distributions, whose value would otherwise be lost in the shuffle.
83			With the default
84			.I -V-
85			setting, the output of rcontrib is a coefficient that must be multiplied
86			by the radiance of each material to arrive at a final contribution.
87			This is more convenient for computing daylight coefficeints, or cases
88			where the actual radiance is not desired.
89			Use the
90			.I -V+
91			setting when you wish to simply sum together contributions
92			(with possible adjustment factors) to obtain a final radiance value.
93			Combined with the
94			.I \-i
95			or
96			.I \-I
97			option, irradiance contributions are reported by
98			.I \-V+
99			rather than radiance, and
100			.I \-V-
101			coefficients contain an additonal factor of PI.
102			.PP
103			The
104			.I \-c
105			option tells
106			.I rcontrib
107			how many rays to accumulate for each record.
108	greg	1.6	The default value is one, meaning a full record will be produced for
109	greg	1.1	each input ray.
110	greg	1.6	For values greater than one, contributions will be averaged together
111	greg	1.1	over the given number of input rays.
112			If set to zero, only a single record will be produced at the very
113			end, corresponding to the sum of all rays given on the input
114			(rather than the average).
115			This is equivalent to passing all the output records through a program like
116			.I total(1)
117			to sum RGB values together, but is much more efficient.
118			Using this option, it is possible to reverse sampling, sending rays from
119			a parallel source such as the sun to a diffuse surface, for example.
120	greg	1.6	Note that output flushing via zero-direction rays is disabled with
121			.I \-c
122			set to zero.
123	greg	1.1	.PP
124	greg	1.18	If progress reports are desired, the
125			.I \-t
126			option specifies a time interval in seconds for reports sent to
127			standard error.
128			.PP
129	greg	1.1	The output of
130			.I rcontrib
131			has many potential uses.
132			Source contributions can be used as components in linear combination to
133			reproduce any desired variation, e.g., simulating lighting controls or
134			changing sky conditions via daylight coefficients.
135			More generally,
136			.I rcontrib
137			can be used to compute arbitrary input-output relationships in optical
138			systems, such as luminaires, light pipes, and shading devices.
139			.PP
140	greg	1.3	.I Rcontrib
141	greg	1.4	sends the accumulated rays tallies
142			to one or more destinations according to the given
143	greg	1.1	.I \-o
144			specification.
145			If a destination begins with an exclamation mark ('!'), then
146			a pipe is opened to a command and data is sent to its standard input.
147			Otherwise, the destination is treated as a file.
148			An existing file of the same name will not be clobbered, unless the
149			.I \-fo
150			option is given.
151			If instead the
152			.I \-r
153			option is specified, data recovery is attempted on existing files.
154			(If
155			.I "\-c 0"
156			is used together with the
157			.I \-r
158			option, existing files are read in and new ray evaluations are added
159			to the previous results, providing a convenient means for
160			progressive simulation.)\0
161			If an output specification contains a "%s" format, this will be
162			replaced by the modifier name.
163			The
164			.I \-b
165			option may be used to further define
166			a "bin number" within each object if finer resolution is needed, and
167			this will be applied to a "%d" format in the output file
168	greg	1.13	specification if present.
169			(The final integer will be offset incrementally
170			if the output is a RADIANCE picture and more than one modifier has
171			the same format specification.)\0
172	greg	1.1	The actual bin number is computed at run time based on ray direction
173			and surface intersection, as described below.
174	greg	1.5	The number of bins must be specified in advance with the
175	greg	1.1	.I \-bn
176			option, and this is critical for output files containing multiple values
177			per record.
178			A variable or constant name may be given for this parameter if
179			it has been defined via a previous
180			.I \-f
181			or
182			.I \-e
183			option.
184	greg	1.6	Since bin numbers start from zero, the bin count is always equal to
185			the last bin plus one.
186	greg	1.1	The most recent
187	greg	1.10	.I \-p,
188	greg	1.1	.I \-b,
189			.I \-bn
190			and
191			.I \-o
192			options to the left of each
193			.I \-m
194			setting are the ones used for that modifier.
195			The ordering of other options is unimportant, except for
196			.I \-x
197			and
198			.I \-y
199			if the
200			.I \-c
201	greg	1.6	is zero, when they control the resolution string
202	greg	1.1	produced in the corresponding output.
203			.PP
204			If a
205			.I \-b
206			expression is defined for a particular modifier,
207			the bin number will be evaluated at run time for each
208	greg	1.4	ray contribution.
209	greg	1.1	Specifically, each ray's world intersection point will be assigned to
210			the variables Px, Py, and Pz, and the normalized ray direction
211			will be assigned to Dx, Dy, and Dz.
212			These parameters may be combined with definitions given in
213			.I \-e
214			arguments and files read using the
215			.I \-f
216			option.
217	greg	1.10	Additional parameter values that apply only to this modifier may be specified
218			with a
219			.I \-p
220			option, which contains a list of variable names and assigned values, separated
221	greg	1.17	by commas, colons, or semicolons.
222	greg	1.1	The computed bin value will be
223			rounded to the nearest whole number.
224	greg	1.9	(Negative bin values will be silently ignored.)\0
225	greg	1.8	For a single bin, you may specify
226			.I "\-b 0",
227			which is the default.
228	greg	1.1	This mechanism allows the user to define precise regions or directions
229			they wish to accumulate, such as the Tregenza sky discretization,
230			which would be otherwise impossible to specify
231			as a set of RADIANCE primitives.
232			The rules and predefined functions available for these expressions are
233			described in the
234			.I rcalc(1)
235			man page.
236	greg	1.8	Like
237	greg	1.1	.I rcalc,
238			.I rcontrib
239			will search the RADIANCE library directories for each file given in a
240			.I \-f
241			option.
242			.PP
243			If no
244			.I \-o
245			specification is given, results are written on the standard output in order
246			of modifier (as given on the command line) then bin number.
247			Concatenated data is also sent to a single destination (i.e., an initial
248			.I \-o
249			specification without formatting strings).
250			If a "%s" format appears but no "%d" in the
251			.I \-o
252			specification, then each modifier will have its own output file, with
253			multiple values per record in the case of a non-zero
254			.I \-b
255			definition.
256			If a "%d" format appears but no "%s", then each bin will get its own
257			output file, with modifiers output in order in each record.
258			For text output, each RGB coefficient triple is separated by a tab,
259			with a newline at the end of each ray record.
260			For binary output formats, there is no such delimiter to mark
261			the end of each record.
262			.PP
263			Input and output format defaults to plain text, where each ray's
264			origin and direction (6 real values) are given on input,
265			and one line is produced per output file per ray.
266			Alternative data representations may be specified by the
267			.I \-f[io]
268			option, which is described in the
269			.I rtrace
270			man page along with the associated
271			.I \-x
272			and
273			.I \-y
274			resolution settings.
275			In particular, the color ('c') output data representation
276			together with positive dimensions for
277			.I \-x
278			and
279			.I \-y
280			will produce an uncompressed RADIANCE picture,
281			suitable for manipulation with
282			.I pcomb(1)
283			and related tools.
284			.PP
285			Options may be given on the command line and/or read from the
286			environment and/or read from a file.
287			A command argument beginning with a dollar sign ('$') is immediately
288			replaced by the contents of the given environment variable.
289			A command argument beginning with an at sign ('@') is immediately
290			replaced by the contents of the given file.
291	greg	1.12	.PP
292			.I Rcontrib
293	rschregle	1.14	supports light source contributions from photon maps generated by
294	greg	1.12	.I mkpmap(1)
295			with its
296			.I -apC
297	rschregle	1.15	option. Enabling photon mapping is described in the
298			.I rtrace
299			man page along with its relevant settings. In photon mapping mode,
300	greg	1.12	.I rcontrib
301			only supports contributions from light sources, not arbitrary modifiers.
302			The
303			.I -b
304			option is supported along with its associated ray variables, as
305			discussed above. Ray coefficients are also supported via the
306			.I \-V-
307			option. Using fewer photons than there are light sources for the photon
308			density estimates results in omitted contributions, thus the bandwidth
309	rschregle	1.15	is clamped accordingly and a warning is issued.
310	greg	1.1	.SH EXAMPLES
311			To compute the proportional contributions from sources modified
312			by "light1" vs. "light2" on a set of illuminance values:
313			.IP "" .2i
314			rcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
315			.PP
316			To generate a pair of images corresponding to these two lights'
317			contributions:
318			.IP "" .2i
319			vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf \|
320			rcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf`
321			@render.opt \-o c_%s.hdr \-m light1 \-m light2 scene.oct
322			.PP
323			These images may then be recombined using the desired outputs
324			of light1 and light2:
325			.IP "" .2i
326			pcomb \-c 100 90 75 c_light1.hdr \-c 50 55 57 c_light2.hdr > combined.hdr
327			.PP
328			To compute an array of illuminance contributions according to a Tregenza sky:
329			.IP "" .2i
330	greg	1.7	rcontrib \-I+ \-f tregenza.cal \-b tbin \-bn Ntbins \-o sky.dat \-m skyglow
331			\-b 0 \-o ground.dat \-m groundglow @render.opt scene.oct < test.dat
332	greg	1.12	.PP
333			To perform an annual simulation of 365 daily sun positions in photon mapping
334			mode:
335			.IP "" .2i
336			rcontrib \-I+ \-h \-V \-fo \-o c_%s.dat \-M lights \-ap contrib.pm 365
337			scene.oct < test.dat,
338	greg	1.1	.SH ENVIRONMENT
339			RAYPATH path to search for \-f and \-M files
340	greg	1.16	.SH BUGS
341			We do not currently compute contributions or coefficients properly
342			in scenes with participating media.
343			A single warning will be issued if a scattering or absorbing medium
344			is detected.
345	greg	1.1	.SH AUTHOR
346			Greg Ward
347			.SH "SEE ALSO"
348	greg	1.12	cnt(1), genklemsamp(1), getinfo(1), mkpmap(1), pcomb(1), pfilt(1),
349			ra_rgbe(1), rcalc(1), rfluxmtx(1), rmtxop(1), rpict(1), rsensor(1),
350			rtrace(1), total(1), vwrays(1), ximage(1)
351