man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.6 2005/06/01 16:11:01 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 "\-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.)\0
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:	1.7
Committed:	Thu Jun 2 04:47:26 2005 UTC (20 years ago) by greg
Branch:	MAIN
Changes since 1.6:	+8 -4 lines
Log Message:	Added binary i/o options to total and piped output to rtcontrib
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.6 2005/06/01 16:11:01 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 "\-e expr"
11	][
12	.B "\-f source"
13	][
14	.B "\-o ospec"
15	][
16	.B "\-b binv"
17	]
18	.B "\-m mod .."
19	[
20	.B $EVAR
21	]
22	[
23	.B @file
24	]
25	[
26	rtrace options
27	]
28	.B octree
29	.br
30	.B "rtcontrib [ options ] \-defaults"
31	.SH DESCRIPTION
32	.I Rtcontrib
33	computes ray contributions (i.e., color coefficients)
34	for objects whose modifiers are named in one or more
35	.I \-m
36	settings.
37	These modifiers are usually materials associated with
38	light sources or sky domes, and must directly modify some geometric
39	primitives to be considered in the output.
40	The output of
41	.I rtcontrib
42	has many potential uses.
43	Source contributions can be used as components in linear combination to
44	reproduce any desired variation, e.g., simulating lighting controls or
45	changing sky conditions via daylight coefficients.
46	More generally,
47	.I rtcontrib
48	can be used to compute arbitrary input-output relationships in optical
49	systems, such as luminaires, light pipes, and shading devices.
50	.PP
51	.I Rtcontrib
52	calls
53	.I rtrace(1)
54	with the -oTW option to calculate the daughter ray
55	contributions for each input ray, and the output tallies
56	are sent to one or more destinations according to the given
57	.I \-o
58	specification.
59	If a destination begins with an exclamation mark ('!'), then
60	a pipe is opened to a command and data is sent to its standard input.
61	Otherwise, the destination is treated as a file.
62	(An existing file of the same name is clobbered.)\0
63	If an output specification contains a "%s" format, this will be
64	replaced by the modifier name.
65	The
66	.I \-b
67	option may be used to further define
68	a "bin number" within each object if finer resolution is needed, and
69	this will be applied to a "%d" format in the output file
70	specification if present.
71	The actual bin number is computed at run time based on ray direction
72	and surface intersection, as described below.
73	The most recent
74	.I \-b
75	and
76	.I \-o
77	options to the left of each
78	.I \-m
79	setting affect only that modifier.
80	(The ordering of other options is unimportant.)\0
81	.PP
82	If a
83	.I \-b
84	expression is defined for a particular modifier,
85	the bin number will be evaluated at run time for each
86	ray contribution from
87	.I rtrace.
88	Specifically, each ray's world intersection point will be assigned to
89	the variables Px, Py, and Pz, and the normalized ray direction
90	will be assigned to Dx, Dy, and Dz.
91	These parameters may be combined with definitions given in
92	.I \-e
93	arguments and files read using the
94	.I \-f
95	option.
96	The computed bin value will be
97	rounded to the nearest whole number.
98	This mechanism allows the user to define precise regions or directions
99	they wish to accumulate, such as the Tregenza sky discretization,
100	which would be otherwise impossible to specify
101	as a set of RADIANCE primitives.
102	The rules and predefined functions available for these expressions are
103	described in the
104	.I rcalc(1)
105	man page.
106	Unlike
107	.I rcalc,
108	.I rtcontrib
109	will search the RADIANCE library directories for each file given in a
110	.I \-f
111	option.
112	(No search takes place if a file name begins with a '.', '/' or '~'
113	character.)\0
114	.PP
115	If no
116	.I \-o
117	specification is given, results are written on the standard output in order
118	of modifier (as given on the command line) then bin number.
119	Concatenated data is also sent to a single destination (i.e., an initial
120	.I \-o
121	specification without formatting strings).
122	If a "%s" format appears but no "%d" in the
123	.I \-o
124	specification, then each modifier will have its own output file, with
125	multiple values per record in the case of a non-zero
126	.I \-b
127	definition.
128	If a "%d" format appears but no "%s", then each bin will get its own
129	output file, with modifiers output in order in each record.
130	For text output, each RGB coefficient triple is separated by a tab,
131	with a newline at the end of each ray record.
132	For binary output formats, there is no such delimiter to mark
133	the end of each record.
134	.PP
135	Input and output format defaults to plain text, where each ray's
136	origin and direction (6 real values) are given on input,
137	and one line is produced per output file per ray.
138	Alternative data representations may be specified by the
139	.I \-f[io]
140	option, which is described in the
141	.I rtrace
142	man page along with the associated
143	.I \-x
144	and
145	.I \-y
146	resolution settings.
147	In particular, the color ('c') output data representation
148	together with positive dimensions for
149	.I \-x
150	and
151	.I \-y
152	will produce an uncompressed RADIANCE picture,
153	suitable for manipulation with
154	.I pcomb(1)
155	and related tools.
156	.PP
157	If the
158	.I \-n
159	option is specified with a value greater than 1, multiple
160	.I rtrace
161	processes will be used to accelerate computation on a shared
162	memory machine.
163	Note that there is no benefit to using more processes
164	than there are local CPUs available to do the work, and the
165	.I rtcontrib
166	process itself may use a considerable amount of CPU time.
167	.PP
168	Options may be given on the command line and/or read from the
169	environment and/or read from a file.
170	A command argument beginning with a dollar sign ('$') is immediately
171	replaced by the contents of the given environment variable.
172	A command argument beginning with an at sign ('@') is immediately
173	replaced by the contents of the given file.
174	.SH EXAMPLES
175	To compute the proportional contributions from sources modified
176	by "light1" vs. "light2" on a set of illuminance values:
177	.IP "" .2i
178	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
179	.PP
180	To generate a pair of images corresponding to these two lights'
181	contributions:
182	.IP "" .2i
183	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
184	rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
185	@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
186	.PP
187	These images may then be recombined using the desired outputs
188	of light1 and light2:
189	.IP "" .2i
190	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
191	.PP
192	To compute an array of illuminance contributions according to a Tregenza sky:
193	.IP "" .2i
194	rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
195	@render.opt -f tregenza.cal scene.oct < test.dat
196	.SH ENVIRONMENT
197	RAYPATH path to search for -f files
198	.SH AUTHOR
199	Greg Ward
200	.SH "SEE ALSO"
201	cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
202	rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)