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 (4 years, 9 months 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
#	Content
1	.\" RCSid "$Id: rcontrib.1,v 1.17 2020/03/14 16:25:46 greg Exp $"
2	.TH RCONTRIB 1 5/25/05 RADIANCE
3	.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	.B "\-t secs"
13	][
14	.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	.B "\-p p1=V1,p2=V2"
27	][
28	.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	.I Rcontrib
50	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	The default value is one, meaning a full record will be produced for
109	each input ray.
110	For values greater than one, contributions will be averaged together
111	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	Note that output flushing via zero-direction rays is disabled with
121	.I \-c
122	set to zero.
123	.PP
124	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	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	.I Rcontrib
141	sends the accumulated rays tallies
142	to one or more destinations according to the given
143	.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	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	The actual bin number is computed at run time based on ray direction
173	and surface intersection, as described below.
174	The number of bins must be specified in advance with the
175	.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	Since bin numbers start from zero, the bin count is always equal to
185	the last bin plus one.
186	The most recent
187	.I \-p,
188	.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	is zero, when they control the resolution string
202	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	ray contribution.
209	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	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	by commas, colons, or semicolons.
222	The computed bin value will be
223	rounded to the nearest whole number.
224	(Negative bin values will be silently ignored.)\0
225	For a single bin, you may specify
226	.I "\-b 0",
227	which is the default.
228	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	Like
237	.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	.PP
292	.I Rcontrib
293	supports light source contributions from photon maps generated by
294	.I mkpmap(1)
295	with its
296	.I -apC
297	option. Enabling photon mapping is described in the
298	.I rtrace
299	man page along with its relevant settings. In photon mapping mode,
300	.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	is clamped accordingly and a warning is issued.
310	.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	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	.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	.SH ENVIRONMENT
339	RAYPATH path to search for \-f and \-M files
340	.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	.SH AUTHOR
346	Greg Ward
347	.SH "SEE ALSO"
348	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