man/man1/rcontrib.1

.\" RCSid "$Id: rcontrib.1,v 1.9 2014/07/19 00:07:03 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), rpict(1), rsensor(1), rtrace(1), total(1), vwrays(1), ximage(1)
Revision:	1.10
Committed:	Sat Jul 19 18:19:33 2014 UTC (10 years, 9 months ago) by greg
Branch:	MAIN
Changes since 1.9:	+9 -1 lines
Log Message:	Added -p option to specify per-modifier function file parameters
#	User	Rev	Content
1	greg	1.10	.\" RCSid "$Id: rcontrib.1,v 1.9 2014/07/19 00:07:03 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			.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	greg	1.10	.B "\-p p1=V1,p2=V2"
25			][
26	greg	1.1	.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	greg	1.3	.I Rcontrib
48	greg	1.1	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	greg	1.6	The default value is one, meaning a full record will be produced for
107	greg	1.1	each input ray.
108	greg	1.6	For values greater than one, contributions will be averaged together
109	greg	1.1	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	greg	1.6	Note that output flushing via zero-direction rays is disabled with
119			.I \-c
120			set to zero.
121	greg	1.1	.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	greg	1.3	.I Rcontrib
134	greg	1.4	sends the accumulated rays tallies
135			to one or more destinations according to the given
136	greg	1.1	.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	greg	1.5	The number of bins must be specified in advance with the
165	greg	1.1	.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	greg	1.6	Since bin numbers start from zero, the bin count is always equal to
175			the last bin plus one.
176	greg	1.1	The most recent
177	greg	1.10	.I \-p,
178	greg	1.1	.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	greg	1.6	is zero, when they control the resolution string
192	greg	1.1	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	greg	1.4	ray contribution.
199	greg	1.1	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	greg	1.10	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	greg	1.1	The computed bin value will be
213			rounded to the nearest whole number.
214	greg	1.9	(Negative bin values will be silently ignored.)\0
215	greg	1.8	For a single bin, you may specify
216			.I "\-b 0",
217			which is the default.
218	greg	1.1	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	greg	1.8	Like
227	greg	1.1	.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	greg	1.7	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	greg	1.1	.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), rpict(1), rsensor(1), rtrace(1), total(1), vwrays(1), ximage(1)