man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.15 2006/02/05 22:22:20 greg Exp $"
.TH RTCONTRIB 1 5/25/05 RADIANCE
.SH NAME
rtcontrib - compute contribution coefficients in a RADIANCE scene
.SH SYNOPSIS
.B rtcontrib
[
.B "\-n nprocs"
][
.B \-V
][
.B \-fo
|
.B \-r
][
.B "\-e expr"
][
.B "\-f source"
][
.B "\-o ospec"
][
.B "\-b binv"
][
.B "\-bn nbins"
]
{
.B "\-m mod | \-M file"
}
..
[
.B $EVAR
]
[
.B @file
]
[
rtrace options
]
.B octree
.br
.B "rtcontrib [ options ] \-defaults"
.SH DESCRIPTION
.I Rtcontrib
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
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 output of
.I rtcontrib
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 rtcontrib
can be used to compute arbitrary input-output relationships in optical
systems, such as luminaires, light pipes, and shading devices.
.PP
.I Rtcontrib
calls
.I rtrace(1)
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
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 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.
If the number of bins is known in advance, it should be specified with the
.I \-bn
option, and this is critical for output files containing multiple values
per record.
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
and
.I \-o
options to the left of each
.I \-m
setting affect only that modifier.
(The ordering of other options is unimportant.)\0
.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 from
.I rtrace.
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.
The computed bin value will be
rounded to the nearest whole number.
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.
Unlike
.I rcalc,
.I rtcontrib
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
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
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
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
.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
.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
.SH ENVIRONMENT
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)
Revision:	1.16
Committed:	Tue Sep 4 17:36:41 2007 UTC (17 years, 9 months ago) by greg
Branch:	MAIN
Changes since 1.15:	+10 -10 lines
Log Message:	Added backslashes in front of hyphens (thanks to Bernd Zeimetz for his effort)
#	User	Rev	Content
1	greg	1.16	.\" RCSid "$Id: rtcontrib.1,v 1.15 2006/02/05 22:22:20 greg Exp $"
2	greg	1.3	.TH RTCONTRIB 1 5/25/05 RADIANCE
3	greg	1.1	.SH NAME
4	greg	1.5	rtcontrib - compute contribution coefficients in a RADIANCE scene
5	greg	1.1	.SH SYNOPSIS
6			.B rtcontrib
7			[
8			.B "\-n nprocs"
9			][
10	greg	1.15	.B \-V
11			][
12	greg	1.14	.B \-fo
13			\|
14	greg	1.8	.B \-r
15			][
16	greg	1.1	.B "\-e expr"
17			][
18			.B "\-f source"
19			][
20	greg	1.7	.B "\-o ospec"
21	greg	1.1	][
22			.B "\-b binv"
23	greg	1.12	][
24			.B "\-bn nbins"
25	greg	1.1	]
26	greg	1.9	{
27			.B "\-m mod \| \-M file"
28			}
29			..
30	greg	1.1	[
31			.B $EVAR
32			]
33			[
34			.B @file
35			]
36			[
37			rtrace options
38			]
39			.B octree
40	greg	1.4	.br
41			.B "rtcontrib [ options ] \-defaults"
42	greg	1.1	.SH DESCRIPTION
43			.I Rtcontrib
44	greg	1.15	computes ray coefficients
45	greg	1.1	for objects whose modifiers are named in one or more
46			.I \-m
47			settings.
48	greg	1.2	These modifiers are usually materials associated with
49			light sources or sky domes, and must directly modify some geometric
50			primitives to be considered in the output.
51	greg	1.9	A modifier list may also be read from a file using the
52			.I \-M
53			option.
54	greg	1.10	The RAYPATH environment variable determines directories to search for
55			this file.
56			(No search takes place if a file name begins with a '.', '/' or '~'
57			character.)\0
58	greg	1.9	.PP
59	greg	1.15	By setting the boolean
60			.I \-V
61			option, you may instruct
62			.I rtcontrib
63			to report the contribution from each material rather than the ray
64			coefficient.
65			This is particularly useful for light sources with directional output
66			distributions, whose value would otherwise be lost in the shuffle.
67			With the default
68			.I -V-
69			setting, the output of rtcontrib is a coefficient that must be multiplied
70			by the radiance of each material to arrive at a final contribution.
71			This is more convenient for computing daylight coefficeints, or cases
72			where the actual radiance is not desired.
73			Use the
74			.I -V+
75			setting when you wish to simply sum together contributions
76			(with possible adjustment factors) to obtain a final radiance value.
77			Combined with the
78			.I \-i
79			or
80			.I \-I
81			option, irradiance contributions are reported by
82			.I \-V+
83			rather than radiance, and
84			.I \-V-
85			coefficients contain an additonal factor of PI.
86			.PP
87	greg	1.3	The output of
88			.I rtcontrib
89			has many potential uses.
90			Source contributions can be used as components in linear combination to
91	greg	1.1	reproduce any desired variation, e.g., simulating lighting controls or
92			changing sky conditions via daylight coefficients.
93			More generally,
94			.I rtcontrib
95	greg	1.3	can be used to compute arbitrary input-output relationships in optical
96			systems, such as luminaires, light pipes, and shading devices.
97	greg	1.1	.PP
98	greg	1.2	.I Rtcontrib
99			calls
100			.I rtrace(1)
101	greg	1.16	with the \-oTW (or \-oTV) option to calculate the daughter ray
102	greg	1.5	contributions for each input ray, and the output tallies
103	greg	1.7	are sent to one or more destinations according to the given
104	greg	1.1	.I \-o
105			specification.
106	greg	1.7	If a destination begins with an exclamation mark ('!'), then
107			a pipe is opened to a command and data is sent to its standard input.
108			Otherwise, the destination is treated as a file.
109	greg	1.14	An existing file of the same name will not be clobbered, unless the
110			.I \-fo
111			option is given.
112			If instead the
113	greg	1.8	.I \-r
114	greg	1.14	option is specified, data recovery is attempted on existing files.
115	greg	1.2	If an output specification contains a "%s" format, this will be
116	greg	1.1	replaced by the modifier name.
117			The
118			.I \-b
119			option may be used to further define
120	greg	1.2	a "bin number" within each object if finer resolution is needed, and
121			this will be applied to a "%d" format in the output file
122	greg	1.1	specification if present.
123	greg	1.3	The actual bin number is computed at run time based on ray direction
124			and surface intersection, as described below.
125	greg	1.12	If the number of bins is known in advance, it should be specified with the
126			.I \-bn
127	greg	1.13	option, and this is critical for output files containing multiple values
128			per record.
129			Since bin numbers start from 0, the bin count is always equal to
130			the last bin plus 1.
131			Set the this value to 0 if the bin count is unknown (the default).
132	greg	1.1	The most recent
133	greg	1.12	.I \-b,
134			.I \-bn
135	greg	1.1	and
136			.I \-o
137	greg	1.2	options to the left of each
138	greg	1.1	.I \-m
139	greg	1.2	setting affect only that modifier.
140			(The ordering of other options is unimportant.)\0
141	greg	1.1	.PP
142	greg	1.2	If a
143			.I \-b
144			expression is defined for a particular modifier,
145			the bin number will be evaluated at run time for each
146			ray contribution from
147			.I rtrace.
148			Specifically, each ray's world intersection point will be assigned to
149			the variables Px, Py, and Pz, and the normalized ray direction
150			will be assigned to Dx, Dy, and Dz.
151			These parameters may be combined with definitions given in
152			.I \-e
153	greg	1.3	arguments and files read using the
154	greg	1.2	.I \-f
155	greg	1.3	option.
156			The computed bin value will be
157	greg	1.2	rounded to the nearest whole number.
158			This mechanism allows the user to define precise regions or directions
159			they wish to accumulate, such as the Tregenza sky discretization,
160			which would be otherwise impossible to specify
161			as a set of RADIANCE primitives.
162	greg	1.3	The rules and predefined functions available for these expressions are
163			described in the
164			.I rcalc(1)
165			man page.
166	greg	1.6	Unlike
167			.I rcalc,
168			.I rtcontrib
169			will search the RADIANCE library directories for each file given in a
170			.I \-f
171			option.
172	greg	1.1	.PP
173			If no
174			.I \-o
175			specification is given, results are written on the standard output in order
176			of modifier (as given on the command line) then bin number.
177	greg	1.7	Concatenated data is also sent to a single destination (i.e., an initial
178	greg	1.2	.I \-o
179			specification without formatting strings).
180	greg	1.1	If a "%s" format appears but no "%d" in the
181			.I \-o
182			specification, then each modifier will have its own output file, with
183			multiple values per record in the case of a non-zero
184			.I \-b
185			definition.
186			If a "%d" format appears but no "%s", then each bin will get its own
187			output file, with modifiers output in order in each record.
188			For text output, each RGB coefficient triple is separated by a tab,
189			with a newline at the end of each ray record.
190			For binary output formats, there is no such delimiter to mark
191			the end of each record.
192			.PP
193	greg	1.2	Input and output format defaults to plain text, where each ray's
194			origin and direction (6 real values) are given on input,
195			and one line is produced per output file per ray.
196			Alternative data representations may be specified by the
197			.I \-f[io]
198			option, which is described in the
199			.I rtrace
200			man page along with the associated
201			.I \-x
202			and
203			.I \-y
204			resolution settings.
205			In particular, the color ('c') output data representation
206			together with positive dimensions for
207			.I \-x
208			and
209			.I \-y
210			will produce an uncompressed RADIANCE picture,
211			suitable for manipulation with
212			.I pcomb(1)
213			and related tools.
214	greg	1.1	.PP
215			If the
216			.I \-n
217			option is specified with a value greater than 1, multiple
218	greg	1.2	.I rtrace
219	greg	1.1	processes will be used to accelerate computation on a shared
220			memory machine.
221			Note that there is no benefit to using more processes
222	greg	1.2	than there are local CPUs available to do the work, and the
223			.I rtcontrib
224			process itself may use a considerable amount of CPU time.
225	greg	1.1	.PP
226			Options may be given on the command line and/or read from the
227			environment and/or read from a file.
228			A command argument beginning with a dollar sign ('$') is immediately
229			replaced by the contents of the given environment variable.
230			A command argument beginning with an at sign ('@') is immediately
231			replaced by the contents of the given file.
232	greg	1.2	.SH EXAMPLES
233			To compute the proportional contributions from sources modified
234			by "light1" vs. "light2" on a set of illuminance values:
235	greg	1.1	.IP "" .2i
236	greg	1.16	rtcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
237	greg	1.2	.PP
238			To generate a pair of images corresponding to these two lights'
239			contributions:
240	greg	1.1	.IP "" .2i
241	greg	1.16	vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf \|
242			rtcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf`
243			@render.opt \-o c_%s.pic \-m light1 \-m light2 scene.oct
244	greg	1.2	.PP
245			These images may then be recombined using the desired outputs
246			of light1 and light2:
247	greg	1.1	.IP "" .2i
248	greg	1.16	pcomb \-c 100 90 75 c_light1.pic \-c 50 55 57 c_light2.pic > combined.pic
249	greg	1.1	.PP
250	greg	1.2	To compute an array of illuminance contributions according to a Tregenza sky:
251			.IP "" .2i
252	greg	1.16	rtcontrib \-I+ \-b tbin \-o sky.dat \-m skyglow \-b 0 \-o ground.dat \-m groundglow
253			@render.opt \-f tregenza.cal scene.oct < test.dat
254	greg	1.6	.SH ENVIRONMENT
255	greg	1.16	RAYPATH path to search for \-f and \-M files
256	greg	1.1	.SH AUTHOR
257			Greg Ward
258			.SH "SEE ALSO"
259			cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
260			rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)