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 (16 years, 8 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)
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.15 2006/02/05 22:22:20 greg Exp $"
2	.TH RTCONTRIB 1 5/25/05 RADIANCE
3	.SH NAME
4	rtcontrib - compute contribution coefficients in a RADIANCE scene
5	.SH SYNOPSIS
6	.B rtcontrib
7	[
8	.B "\-n nprocs"
9	][
10	.B \-V
11	][
12	.B \-fo
13	\|
14	.B \-r
15	][
16	.B "\-e expr"
17	][
18	.B "\-f source"
19	][
20	.B "\-o ospec"
21	][
22	.B "\-b binv"
23	][
24	.B "\-bn nbins"
25	]
26	{
27	.B "\-m mod \| \-M file"
28	}
29	..
30	[
31	.B $EVAR
32	]
33	[
34	.B @file
35	]
36	[
37	rtrace options
38	]
39	.B octree
40	.br
41	.B "rtcontrib [ options ] \-defaults"
42	.SH DESCRIPTION
43	.I Rtcontrib
44	computes ray coefficients
45	for objects whose modifiers are named in one or more
46	.I \-m
47	settings.
48	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	A modifier list may also be read from a file using the
52	.I \-M
53	option.
54	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	.PP
59	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	The output of
88	.I rtcontrib
89	has many potential uses.
90	Source contributions can be used as components in linear combination to
91	reproduce any desired variation, e.g., simulating lighting controls or
92	changing sky conditions via daylight coefficients.
93	More generally,
94	.I rtcontrib
95	can be used to compute arbitrary input-output relationships in optical
96	systems, such as luminaires, light pipes, and shading devices.
97	.PP
98	.I Rtcontrib
99	calls
100	.I rtrace(1)
101	with the \-oTW (or \-oTV) option to calculate the daughter ray
102	contributions for each input ray, and the output tallies
103	are sent to one or more destinations according to the given
104	.I \-o
105	specification.
106	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	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	.I \-r
114	option is specified, data recovery is attempted on existing files.
115	If an output specification contains a "%s" format, this will be
116	replaced by the modifier name.
117	The
118	.I \-b
119	option may be used to further define
120	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	specification if present.
123	The actual bin number is computed at run time based on ray direction
124	and surface intersection, as described below.
125	If the number of bins is known in advance, it should be specified with the
126	.I \-bn
127	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	The most recent
133	.I \-b,
134	.I \-bn
135	and
136	.I \-o
137	options to the left of each
138	.I \-m
139	setting affect only that modifier.
140	(The ordering of other options is unimportant.)\0
141	.PP
142	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	arguments and files read using the
154	.I \-f
155	option.
156	The computed bin value will be
157	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	The rules and predefined functions available for these expressions are
163	described in the
164	.I rcalc(1)
165	man page.
166	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	.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	Concatenated data is also sent to a single destination (i.e., an initial
178	.I \-o
179	specification without formatting strings).
180	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	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	.PP
215	If the
216	.I \-n
217	option is specified with a value greater than 1, multiple
218	.I rtrace
219	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	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	.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	.SH EXAMPLES
233	To compute the proportional contributions from sources modified
234	by "light1" vs. "light2" on a set of illuminance values:
235	.IP "" .2i
236	rtcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
237	.PP
238	To generate a pair of images corresponding to these two lights'
239	contributions:
240	.IP "" .2i
241	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	.PP
245	These images may then be recombined using the desired outputs
246	of light1 and light2:
247	.IP "" .2i
248	pcomb \-c 100 90 75 c_light1.pic \-c 50 55 57 c_light2.pic > combined.pic
249	.PP
250	To compute an array of illuminance contributions according to a Tregenza sky:
251	.IP "" .2i
252	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	.SH ENVIRONMENT
255	RAYPATH path to search for \-f and \-M files
256	.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)