man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.10 2005/06/10 20:53:55 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.
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
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.
.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:	1.11
Committed:	Sat Jul 23 19:53:36 2005 UTC (19 years, 3 months ago) by greg
Branch:	MAIN
CVS Tags:	rad3R7P1, rad3R7P2
Changes since 1.10:	+2 -2 lines
Log Message:	Minor fix in example
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.10 2005/06/10 20:53:55 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	The RAYPATH environment variable determines directories to search for
49	this file.
50	(No search takes place if a file name begins with a '.', '/' or '~'
51	character.)\0
52	.PP
53	The output of
54	.I rtcontrib
55	has many potential uses.
56	Source contributions can be used as components in linear combination to
57	reproduce any desired variation, e.g., simulating lighting controls or
58	changing sky conditions via daylight coefficients.
59	More generally,
60	.I rtcontrib
61	can be used to compute arbitrary input-output relationships in optical
62	systems, such as luminaires, light pipes, and shading devices.
63	.PP
64	.I Rtcontrib
65	calls
66	.I rtrace(1)
67	with the -oTW option to calculate the daughter ray
68	contributions for each input ray, and the output tallies
69	are sent to one or more destinations according to the given
70	.I \-o
71	specification.
72	If a destination begins with an exclamation mark ('!'), then
73	a pipe is opened to a command and data is sent to its standard input.
74	Otherwise, the destination is treated as a file.
75	An existing file of the same name is clobbered, unless the
76	.I \-r
77	option is specified, in which case data recovery is attempted.
78	If an output specification contains a "%s" format, this will be
79	replaced by the modifier name.
80	The
81	.I \-b
82	option may be used to further define
83	a "bin number" within each object if finer resolution is needed, and
84	this will be applied to a "%d" format in the output file
85	specification if present.
86	The actual bin number is computed at run time based on ray direction
87	and surface intersection, as described below.
88	The most recent
89	.I \-b
90	and
91	.I \-o
92	options to the left of each
93	.I \-m
94	setting affect only that modifier.
95	(The ordering of other options is unimportant.)\0
96	.PP
97	If a
98	.I \-b
99	expression is defined for a particular modifier,
100	the bin number will be evaluated at run time for each
101	ray contribution from
102	.I rtrace.
103	Specifically, each ray's world intersection point will be assigned to
104	the variables Px, Py, and Pz, and the normalized ray direction
105	will be assigned to Dx, Dy, and Dz.
106	These parameters may be combined with definitions given in
107	.I \-e
108	arguments and files read using the
109	.I \-f
110	option.
111	The computed bin value will be
112	rounded to the nearest whole number.
113	This mechanism allows the user to define precise regions or directions
114	they wish to accumulate, such as the Tregenza sky discretization,
115	which would be otherwise impossible to specify
116	as a set of RADIANCE primitives.
117	The rules and predefined functions available for these expressions are
118	described in the
119	.I rcalc(1)
120	man page.
121	Unlike
122	.I rcalc,
123	.I rtcontrib
124	will search the RADIANCE library directories for each file given in a
125	.I \-f
126	option.
127	.PP
128	If no
129	.I \-o
130	specification is given, results are written on the standard output in order
131	of modifier (as given on the command line) then bin number.
132	Concatenated data is also sent to a single destination (i.e., an initial
133	.I \-o
134	specification without formatting strings).
135	If a "%s" format appears but no "%d" in the
136	.I \-o
137	specification, then each modifier will have its own output file, with
138	multiple values per record in the case of a non-zero
139	.I \-b
140	definition.
141	If a "%d" format appears but no "%s", then each bin will get its own
142	output file, with modifiers output in order in each record.
143	For text output, each RGB coefficient triple is separated by a tab,
144	with a newline at the end of each ray record.
145	For binary output formats, there is no such delimiter to mark
146	the end of each record.
147	.PP
148	Input and output format defaults to plain text, where each ray's
149	origin and direction (6 real values) are given on input,
150	and one line is produced per output file per ray.
151	Alternative data representations may be specified by the
152	.I \-f[io]
153	option, which is described in the
154	.I rtrace
155	man page along with the associated
156	.I \-x
157	and
158	.I \-y
159	resolution settings.
160	In particular, the color ('c') output data representation
161	together with positive dimensions for
162	.I \-x
163	and
164	.I \-y
165	will produce an uncompressed RADIANCE picture,
166	suitable for manipulation with
167	.I pcomb(1)
168	and related tools.
169	.PP
170	If the
171	.I \-n
172	option is specified with a value greater than 1, multiple
173	.I rtrace
174	processes will be used to accelerate computation on a shared
175	memory machine.
176	Note that there is no benefit to using more processes
177	than there are local CPUs available to do the work, and the
178	.I rtcontrib
179	process itself may use a considerable amount of CPU time.
180	.PP
181	Options may be given on the command line and/or read from the
182	environment and/or read from a file.
183	A command argument beginning with a dollar sign ('$') is immediately
184	replaced by the contents of the given environment variable.
185	A command argument beginning with an at sign ('@') is immediately
186	replaced by the contents of the given file.
187	.SH EXAMPLES
188	To compute the proportional contributions from sources modified
189	by "light1" vs. "light2" on a set of illuminance values:
190	.IP "" .2i
191	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
192	.PP
193	To generate a pair of images corresponding to these two lights'
194	contributions:
195	.IP "" .2i
196	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
197	rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
198	@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
199	.PP
200	These images may then be recombined using the desired outputs
201	of light1 and light2:
202	.IP "" .2i
203	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
204	.PP
205	To compute an array of illuminance contributions according to a Tregenza sky:
206	.IP "" .2i
207	rtcontrib -I+ -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
208	@render.opt -f tregenza.cal scene.oct < test.dat
209	.SH ENVIRONMENT
210	RAYPATH path to search for -f and -M files
211	.SH AUTHOR
212	Greg Ward
213	.SH "SEE ALSO"
214	cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
215	rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)