man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.8 2005/06/09 17:27:27 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 | \-M file"
}
..
[
.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.
A modifier list may also be read from a file using the
.I \-M
option.
.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 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:	1.9
Committed:	Fri Jun 10 16:42:10 2005 UTC (19 years ago) by greg
Branch:	MAIN
Changes since 1.8:	+9 -2 lines
Log Message:	Added rtcontrib -M option to read modifier list from a file
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.8 2005/06/09 17:27:27 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	{
21	.B "\-m mod \| \-M file"
22	}
23	..
24	[
25	.B $EVAR
26	]
27	[
28	.B @file
29	]
30	[
31	rtrace options
32	]
33	.B octree
34	.br
35	.B "rtcontrib [ options ] \-defaults"
36	.SH DESCRIPTION
37	.I Rtcontrib
38	computes ray contributions (i.e., color coefficients)
39	for objects whose modifiers are named in one or more
40	.I \-m
41	settings.
42	These modifiers are usually materials associated with
43	light sources or sky domes, and must directly modify some geometric
44	primitives to be considered in the output.
45	A modifier list may also be read from a file using the
46	.I \-M
47	option.
48	.PP
49	The output of
50	.I rtcontrib
51	has many potential uses.
52	Source contributions can be used as components in linear combination to
53	reproduce any desired variation, e.g., simulating lighting controls or
54	changing sky conditions via daylight coefficients.
55	More generally,
56	.I rtcontrib
57	can be used to compute arbitrary input-output relationships in optical
58	systems, such as luminaires, light pipes, and shading devices.
59	.PP
60	.I Rtcontrib
61	calls
62	.I rtrace(1)
63	with the -oTW option to calculate the daughter ray
64	contributions for each input ray, and the output tallies
65	are sent to one or more destinations according to the given
66	.I \-o
67	specification.
68	If a destination begins with an exclamation mark ('!'), then
69	a pipe is opened to a command and data is sent to its standard input.
70	Otherwise, the destination is treated as a file.
71	An existing file of the same name is clobbered, unless the
72	.I \-r
73	option is specified, in which case data recovery is attempted.
74	If an output specification contains a "%s" format, this will be
75	replaced by the modifier name.
76	The
77	.I \-b
78	option may be used to further define
79	a "bin number" within each object if finer resolution is needed, and
80	this will be applied to a "%d" format in the output file
81	specification if present.
82	The actual bin number is computed at run time based on ray direction
83	and surface intersection, as described below.
84	The most recent
85	.I \-b
86	and
87	.I \-o
88	options to the left of each
89	.I \-m
90	setting affect only that modifier.
91	(The ordering of other options is unimportant.)\0
92	.PP
93	If a
94	.I \-b
95	expression is defined for a particular modifier,
96	the bin number will be evaluated at run time for each
97	ray contribution from
98	.I rtrace.
99	Specifically, each ray's world intersection point will be assigned to
100	the variables Px, Py, and Pz, and the normalized ray direction
101	will be assigned to Dx, Dy, and Dz.
102	These parameters may be combined with definitions given in
103	.I \-e
104	arguments and files read using the
105	.I \-f
106	option.
107	The computed bin value will be
108	rounded to the nearest whole number.
109	This mechanism allows the user to define precise regions or directions
110	they wish to accumulate, such as the Tregenza sky discretization,
111	which would be otherwise impossible to specify
112	as a set of RADIANCE primitives.
113	The rules and predefined functions available for these expressions are
114	described in the
115	.I rcalc(1)
116	man page.
117	Unlike
118	.I rcalc,
119	.I rtcontrib
120	will search the RADIANCE library directories for each file given in a
121	.I \-f
122	option.
123	(No search takes place if a file name begins with a '.', '/' or '~'
124	character.)\0
125	.PP
126	If no
127	.I \-o
128	specification is given, results are written on the standard output in order
129	of modifier (as given on the command line) then bin number.
130	Concatenated data is also sent to a single destination (i.e., an initial
131	.I \-o
132	specification without formatting strings).
133	If a "%s" format appears but no "%d" in the
134	.I \-o
135	specification, then each modifier will have its own output file, with
136	multiple values per record in the case of a non-zero
137	.I \-b
138	definition.
139	If a "%d" format appears but no "%s", then each bin will get its own
140	output file, with modifiers output in order in each record.
141	For text output, each RGB coefficient triple is separated by a tab,
142	with a newline at the end of each ray record.
143	For binary output formats, there is no such delimiter to mark
144	the end of each record.
145	.PP
146	Input and output format defaults to plain text, where each ray's
147	origin and direction (6 real values) are given on input,
148	and one line is produced per output file per ray.
149	Alternative data representations may be specified by the
150	.I \-f[io]
151	option, which is described in the
152	.I rtrace
153	man page along with the associated
154	.I \-x
155	and
156	.I \-y
157	resolution settings.
158	In particular, the color ('c') output data representation
159	together with positive dimensions for
160	.I \-x
161	and
162	.I \-y
163	will produce an uncompressed RADIANCE picture,
164	suitable for manipulation with
165	.I pcomb(1)
166	and related tools.
167	.PP
168	If the
169	.I \-n
170	option is specified with a value greater than 1, multiple
171	.I rtrace
172	processes will be used to accelerate computation on a shared
173	memory machine.
174	Note that there is no benefit to using more processes
175	than there are local CPUs available to do the work, and the
176	.I rtcontrib
177	process itself may use a considerable amount of CPU time.
178	.PP
179	Options may be given on the command line and/or read from the
180	environment and/or read from a file.
181	A command argument beginning with a dollar sign ('$') is immediately
182	replaced by the contents of the given environment variable.
183	A command argument beginning with an at sign ('@') is immediately
184	replaced by the contents of the given file.
185	.SH EXAMPLES
186	To compute the proportional contributions from sources modified
187	by "light1" vs. "light2" on a set of illuminance values:
188	.IP "" .2i
189	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
190	.PP
191	To generate a pair of images corresponding to these two lights'
192	contributions:
193	.IP "" .2i
194	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
195	rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
196	@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
197	.PP
198	These images may then be recombined using the desired outputs
199	of light1 and light2:
200	.IP "" .2i
201	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
202	.PP
203	To compute an array of illuminance contributions according to a Tregenza sky:
204	.IP "" .2i
205	rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
206	@render.opt -f tregenza.cal scene.oct < test.dat
207	.SH ENVIRONMENT
208	RAYPATH path to search for -f files
209	.SH AUTHOR
210	Greg Ward
211	.SH "SEE ALSO"
212	cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
213	rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)