man/man1/rcontrib.1

.\" RCSid "$Id: rcontrib.1,v 1.10 2014/07/19 18:19:33 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 "\-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
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 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 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.
.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
.SH ENVIRONMENT
RAYPATH         path to search for \-f and \-M files
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
cnt(1), genklemsamp(1), getinfo(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:	1.11
Committed:	Tue Jul 22 21:55:31 2014 UTC (9 years, 10 months ago) by greg
Branch:	MAIN
CVS Tags:	rad4R2P2, rad4R2, rad4R2P1
Changes since 1.10:	+3 -2 lines
Log Message:	Created man page for rfluxmtx and added some error checks
#	Content
1	.\" RCSid "$Id: rcontrib.1,v 1.10 2014/07/19 18:19:33 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 "\-c count"
13	][
14	.B \-fo
15	\|
16	.B \-r
17	][
18	.B "\-e expr"
19	][
20	.B "\-f source"
21	][
22	.B "\-o ospec"
23	][
24	.B "\-p p1=V1,p2=V2"
25	][
26	.B "\-b binv"
27	][
28	.B "\-bn nbins"
29	]
30	{
31	.B "\-m mod \| \-M file"
32	}
33	..
34	[
35	.B $EVAR
36	]
37	[
38	.B @file
39	]
40	[
41	rtrace options
42	]
43	.B octree
44	.br
45	.B "rcontrib [ options ] \-defaults"
46	.SH DESCRIPTION
47	.I Rcontrib
48	computes ray coefficients
49	for objects whose modifiers are named in one or more
50	.I \-m
51	settings.
52	These modifiers are usually materials associated with
53	light sources or sky domes, and must directly modify some geometric
54	primitives to be considered in the output.
55	A modifier list may also be read from a file using the
56	.I \-M
57	option.
58	The RAYPATH environment variable determines directories to search for
59	this file.
60	(No search takes place if a file name begins with a '.', '/' or '~'
61	character.)\0
62	.PP
63	If the
64	.I \-n
65	option is specified with a value greater than 1, multiple
66	processes will be used to accelerate computation on a shared
67	memory machine.
68	Note that there is no benefit to using more processes
69	than there are local CPUs available to do the work, and the
70	.I rcontrib
71	process itself may use a considerable amount of CPU time.
72	.PP
73	By setting the boolean
74	.I \-V
75	option, you may instruct
76	.I rcontrib
77	to report the contribution from each material rather than the ray
78	coefficient.
79	This is particularly useful for light sources with directional output
80	distributions, whose value would otherwise be lost in the shuffle.
81	With the default
82	.I -V-
83	setting, the output of rcontrib is a coefficient that must be multiplied
84	by the radiance of each material to arrive at a final contribution.
85	This is more convenient for computing daylight coefficeints, or cases
86	where the actual radiance is not desired.
87	Use the
88	.I -V+
89	setting when you wish to simply sum together contributions
90	(with possible adjustment factors) to obtain a final radiance value.
91	Combined with the
92	.I \-i
93	or
94	.I \-I
95	option, irradiance contributions are reported by
96	.I \-V+
97	rather than radiance, and
98	.I \-V-
99	coefficients contain an additonal factor of PI.
100	.PP
101	The
102	.I \-c
103	option tells
104	.I rcontrib
105	how many rays to accumulate for each record.
106	The default value is one, meaning a full record will be produced for
107	each input ray.
108	For values greater than one, contributions will be averaged together
109	over the given number of input rays.
110	If set to zero, only a single record will be produced at the very
111	end, corresponding to the sum of all rays given on the input
112	(rather than the average).
113	This is equivalent to passing all the output records through a program like
114	.I total(1)
115	to sum RGB values together, but is much more efficient.
116	Using this option, it is possible to reverse sampling, sending rays from
117	a parallel source such as the sun to a diffuse surface, for example.
118	Note that output flushing via zero-direction rays is disabled with
119	.I \-c
120	set to zero.
121	.PP
122	The output of
123	.I rcontrib
124	has many potential uses.
125	Source contributions can be used as components in linear combination to
126	reproduce any desired variation, e.g., simulating lighting controls or
127	changing sky conditions via daylight coefficients.
128	More generally,
129	.I rcontrib
130	can be used to compute arbitrary input-output relationships in optical
131	systems, such as luminaires, light pipes, and shading devices.
132	.PP
133	.I Rcontrib
134	sends the accumulated rays tallies
135	to one or more destinations according to the given
136	.I \-o
137	specification.
138	If a destination begins with an exclamation mark ('!'), then
139	a pipe is opened to a command and data is sent to its standard input.
140	Otherwise, the destination is treated as a file.
141	An existing file of the same name will not be clobbered, unless the
142	.I \-fo
143	option is given.
144	If instead the
145	.I \-r
146	option is specified, data recovery is attempted on existing files.
147	(If
148	.I "\-c 0"
149	is used together with the
150	.I \-r
151	option, existing files are read in and new ray evaluations are added
152	to the previous results, providing a convenient means for
153	progressive simulation.)\0
154	If an output specification contains a "%s" format, this will be
155	replaced by the modifier name.
156	The
157	.I \-b
158	option may be used to further define
159	a "bin number" within each object if finer resolution is needed, and
160	this will be applied to a "%d" format in the output file
161	specification if present.
162	The actual bin number is computed at run time based on ray direction
163	and surface intersection, as described below.
164	The number of bins must be specified in advance with the
165	.I \-bn
166	option, and this is critical for output files containing multiple values
167	per record.
168	A variable or constant name may be given for this parameter if
169	it has been defined via a previous
170	.I \-f
171	or
172	.I \-e
173	option.
174	Since bin numbers start from zero, the bin count is always equal to
175	the last bin plus one.
176	The most recent
177	.I \-p,
178	.I \-b,
179	.I \-bn
180	and
181	.I \-o
182	options to the left of each
183	.I \-m
184	setting are the ones used for that modifier.
185	The ordering of other options is unimportant, except for
186	.I \-x
187	and
188	.I \-y
189	if the
190	.I \-c
191	is zero, when they control the resolution string
192	produced in the corresponding output.
193	.PP
194	If a
195	.I \-b
196	expression is defined for a particular modifier,
197	the bin number will be evaluated at run time for each
198	ray contribution.
199	Specifically, each ray's world intersection point will be assigned to
200	the variables Px, Py, and Pz, and the normalized ray direction
201	will be assigned to Dx, Dy, and Dz.
202	These parameters may be combined with definitions given in
203	.I \-e
204	arguments and files read using the
205	.I \-f
206	option.
207	Additional parameter values that apply only to this modifier may be specified
208	with a
209	.I \-p
210	option, which contains a list of variable names and assigned values, separated
211	by commas or semicolons.
212	The computed bin value will be
213	rounded to the nearest whole number.
214	(Negative bin values will be silently ignored.)\0
215	For a single bin, you may specify
216	.I "\-b 0",
217	which is the default.
218	This mechanism allows the user to define precise regions or directions
219	they wish to accumulate, such as the Tregenza sky discretization,
220	which would be otherwise impossible to specify
221	as a set of RADIANCE primitives.
222	The rules and predefined functions available for these expressions are
223	described in the
224	.I rcalc(1)
225	man page.
226	Like
227	.I rcalc,
228	.I rcontrib
229	will search the RADIANCE library directories for each file given in a
230	.I \-f
231	option.
232	.PP
233	If no
234	.I \-o
235	specification is given, results are written on the standard output in order
236	of modifier (as given on the command line) then bin number.
237	Concatenated data is also sent to a single destination (i.e., an initial
238	.I \-o
239	specification without formatting strings).
240	If a "%s" format appears but no "%d" in the
241	.I \-o
242	specification, then each modifier will have its own output file, with
243	multiple values per record in the case of a non-zero
244	.I \-b
245	definition.
246	If a "%d" format appears but no "%s", then each bin will get its own
247	output file, with modifiers output in order in each record.
248	For text output, each RGB coefficient triple is separated by a tab,
249	with a newline at the end of each ray record.
250	For binary output formats, there is no such delimiter to mark
251	the end of each record.
252	.PP
253	Input and output format defaults to plain text, where each ray's
254	origin and direction (6 real values) are given on input,
255	and one line is produced per output file per ray.
256	Alternative data representations may be specified by the
257	.I \-f[io]
258	option, which is described in the
259	.I rtrace
260	man page along with the associated
261	.I \-x
262	and
263	.I \-y
264	resolution settings.
265	In particular, the color ('c') output data representation
266	together with positive dimensions for
267	.I \-x
268	and
269	.I \-y
270	will produce an uncompressed RADIANCE picture,
271	suitable for manipulation with
272	.I pcomb(1)
273	and related tools.
274	.PP
275	Options may be given on the command line and/or read from the
276	environment and/or read from a file.
277	A command argument beginning with a dollar sign ('$') is immediately
278	replaced by the contents of the given environment variable.
279	A command argument beginning with an at sign ('@') is immediately
280	replaced by the contents of the given file.
281	.SH EXAMPLES
282	To compute the proportional contributions from sources modified
283	by "light1" vs. "light2" on a set of illuminance values:
284	.IP "" .2i
285	rcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
286	.PP
287	To generate a pair of images corresponding to these two lights'
288	contributions:
289	.IP "" .2i
290	vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf \|
291	rcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf`
292	@render.opt \-o c_%s.hdr \-m light1 \-m light2 scene.oct
293	.PP
294	These images may then be recombined using the desired outputs
295	of light1 and light2:
296	.IP "" .2i
297	pcomb \-c 100 90 75 c_light1.hdr \-c 50 55 57 c_light2.hdr > combined.hdr
298	.PP
299	To compute an array of illuminance contributions according to a Tregenza sky:
300	.IP "" .2i
301	rcontrib \-I+ \-f tregenza.cal \-b tbin \-bn Ntbins \-o sky.dat \-m skyglow
302	\-b 0 \-o ground.dat \-m groundglow @render.opt scene.oct < test.dat
303	.SH ENVIRONMENT
304	RAYPATH path to search for \-f and \-M files
305	.SH AUTHOR
306	Greg Ward
307	.SH "SEE ALSO"
308	cnt(1), genklemsamp(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
309	rcalc(1), rfluxmtx(1), rmtxop(1),
310	rpict(1), rsensor(1), rtrace(1), total(1), vwrays(1), ximage(1)