man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.7 2005/06/02 04:47:26 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 \-r
][
.B "\-e expr"
][
.B "\-f source"
][
.B "\-o ospec"
][
.B "\-b binv"
]
.B "\-m mod .."
[
.B $EVAR
]
[
.B @file
]
[
rtrace options
]
.B octree
.br
.B "rtcontrib [ options ] \-defaults"
.SH DESCRIPTION
.I Rtcontrib
computes ray contributions (i.e., color 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.
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 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 is clobbered, unless the
.I \-r
option is specified, in which case data recovery is attempted.
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 most recent
.I \-b
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.
(No search takes place if a file name begins with a '.', '/' or '~'
character.)\0
.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 -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 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:	1.8
Committed:	Thu Jun 9 17:27:27 2005 UTC (20 years ago) by greg
Branch:	MAIN
Changes since 1.7:	+6 -2 lines
Log Message:	Implementaed rtcontrib -r (recover) option, added MODIFIER= + BIN= to header
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.7 2005/06/02 04:47:26 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 \-r
11	][
12	.B "\-e expr"
13	][
14	.B "\-f source"
15	][
16	.B "\-o ospec"
17	][
18	.B "\-b binv"
19	]
20	.B "\-m mod .."
21	[
22	.B $EVAR
23	]
24	[
25	.B @file
26	]
27	[
28	rtrace options
29	]
30	.B octree
31	.br
32	.B "rtcontrib [ options ] \-defaults"
33	.SH DESCRIPTION
34	.I Rtcontrib
35	computes ray contributions (i.e., color coefficients)
36	for objects whose modifiers are named in one or more
37	.I \-m
38	settings.
39	These modifiers are usually materials associated with
40	light sources or sky domes, and must directly modify some geometric
41	primitives to be considered in the output.
42	The output of
43	.I rtcontrib
44	has many potential uses.
45	Source contributions can be used as components in linear combination to
46	reproduce any desired variation, e.g., simulating lighting controls or
47	changing sky conditions via daylight coefficients.
48	More generally,
49	.I rtcontrib
50	can be used to compute arbitrary input-output relationships in optical
51	systems, such as luminaires, light pipes, and shading devices.
52	.PP
53	.I Rtcontrib
54	calls
55	.I rtrace(1)
56	with the -oTW option to calculate the daughter ray
57	contributions for each input ray, and the output tallies
58	are sent to one or more destinations according to the given
59	.I \-o
60	specification.
61	If a destination begins with an exclamation mark ('!'), then
62	a pipe is opened to a command and data is sent to its standard input.
63	Otherwise, the destination is treated as a file.
64	An existing file of the same name is clobbered, unless the
65	.I \-r
66	option is specified, in which case data recovery is attempted.
67	If an output specification contains a "%s" format, this will be
68	replaced by the modifier name.
69	The
70	.I \-b
71	option may be used to further define
72	a "bin number" within each object if finer resolution is needed, and
73	this will be applied to a "%d" format in the output file
74	specification if present.
75	The actual bin number is computed at run time based on ray direction
76	and surface intersection, as described below.
77	The most recent
78	.I \-b
79	and
80	.I \-o
81	options to the left of each
82	.I \-m
83	setting affect only that modifier.
84	(The ordering of other options is unimportant.)\0
85	.PP
86	If a
87	.I \-b
88	expression is defined for a particular modifier,
89	the bin number will be evaluated at run time for each
90	ray contribution from
91	.I rtrace.
92	Specifically, each ray's world intersection point will be assigned to
93	the variables Px, Py, and Pz, and the normalized ray direction
94	will be assigned to Dx, Dy, and Dz.
95	These parameters may be combined with definitions given in
96	.I \-e
97	arguments and files read using the
98	.I \-f
99	option.
100	The computed bin value will be
101	rounded to the nearest whole number.
102	This mechanism allows the user to define precise regions or directions
103	they wish to accumulate, such as the Tregenza sky discretization,
104	which would be otherwise impossible to specify
105	as a set of RADIANCE primitives.
106	The rules and predefined functions available for these expressions are
107	described in the
108	.I rcalc(1)
109	man page.
110	Unlike
111	.I rcalc,
112	.I rtcontrib
113	will search the RADIANCE library directories for each file given in a
114	.I \-f
115	option.
116	(No search takes place if a file name begins with a '.', '/' or '~'
117	character.)\0
118	.PP
119	If no
120	.I \-o
121	specification is given, results are written on the standard output in order
122	of modifier (as given on the command line) then bin number.
123	Concatenated data is also sent to a single destination (i.e., an initial
124	.I \-o
125	specification without formatting strings).
126	If a "%s" format appears but no "%d" in the
127	.I \-o
128	specification, then each modifier will have its own output file, with
129	multiple values per record in the case of a non-zero
130	.I \-b
131	definition.
132	If a "%d" format appears but no "%s", then each bin will get its own
133	output file, with modifiers output in order in each record.
134	For text output, each RGB coefficient triple is separated by a tab,
135	with a newline at the end of each ray record.
136	For binary output formats, there is no such delimiter to mark
137	the end of each record.
138	.PP
139	Input and output format defaults to plain text, where each ray's
140	origin and direction (6 real values) are given on input,
141	and one line is produced per output file per ray.
142	Alternative data representations may be specified by the
143	.I \-f[io]
144	option, which is described in the
145	.I rtrace
146	man page along with the associated
147	.I \-x
148	and
149	.I \-y
150	resolution settings.
151	In particular, the color ('c') output data representation
152	together with positive dimensions for
153	.I \-x
154	and
155	.I \-y
156	will produce an uncompressed RADIANCE picture,
157	suitable for manipulation with
158	.I pcomb(1)
159	and related tools.
160	.PP
161	If the
162	.I \-n
163	option is specified with a value greater than 1, multiple
164	.I rtrace
165	processes will be used to accelerate computation on a shared
166	memory machine.
167	Note that there is no benefit to using more processes
168	than there are local CPUs available to do the work, and the
169	.I rtcontrib
170	process itself may use a considerable amount of CPU time.
171	.PP
172	Options may be given on the command line and/or read from the
173	environment and/or read from a file.
174	A command argument beginning with a dollar sign ('$') is immediately
175	replaced by the contents of the given environment variable.
176	A command argument beginning with an at sign ('@') is immediately
177	replaced by the contents of the given file.
178	.SH EXAMPLES
179	To compute the proportional contributions from sources modified
180	by "light1" vs. "light2" on a set of illuminance values:
181	.IP "" .2i
182	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
183	.PP
184	To generate a pair of images corresponding to these two lights'
185	contributions:
186	.IP "" .2i
187	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
188	rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
189	@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
190	.PP
191	These images may then be recombined using the desired outputs
192	of light1 and light2:
193	.IP "" .2i
194	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
195	.PP
196	To compute an array of illuminance contributions according to a Tregenza sky:
197	.IP "" .2i
198	rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
199	@render.opt -f tregenza.cal scene.oct < test.dat
200	.SH ENVIRONMENT
201	RAYPATH path to search for -f files
202	.SH AUTHOR
203	Greg Ward
204	.SH "SEE ALSO"
205	cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
206	rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)