man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.5 2005/05/27 19:15:28 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 fspec"
][
.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 files according to the given
.I \-o
specification.
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 lone output file (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:	1.6
Committed:	Wed Jun 1 16:11:01 2005 UTC (18 years, 11 months ago) by greg
Branch:	MAIN
Changes since 1.5:	+11 -1 lines
Log Message:	Added RAYPATH directory searching to rtcontrib -f option
#	User	Rev	Content
1	greg	1.6	.\" RCSid "$Id: rtcontrib.1,v 1.5 2005/05/27 19:15:28 greg Exp $"
2	greg	1.3	.TH RTCONTRIB 1 5/25/05 RADIANCE
3	greg	1.1	.SH NAME
4	greg	1.5	rtcontrib - compute contribution coefficients in a RADIANCE scene
5	greg	1.1	.SH SYNOPSIS
6			.B rtcontrib
7			[
8			.B "\-n nprocs"
9			][
10			.B "\-e expr"
11			][
12			.B "\-f source"
13			][
14			.B "\-o fspec"
15			][
16			.B "\-b binv"
17			]
18	greg	1.2	.B "\-m mod .."
19	greg	1.1	[
20			.B $EVAR
21			]
22			[
23			.B @file
24			]
25			[
26			rtrace options
27			]
28			.B octree
29	greg	1.4	.br
30			.B "rtcontrib [ options ] \-defaults"
31	greg	1.1	.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	greg	1.2	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	greg	1.3	The output of
41			.I rtcontrib
42			has many potential uses.
43			Source contributions can be used as components in linear combination to
44	greg	1.1	reproduce any desired variation, e.g., simulating lighting controls or
45			changing sky conditions via daylight coefficients.
46			More generally,
47			.I rtcontrib
48	greg	1.3	can be used to compute arbitrary input-output relationships in optical
49			systems, such as luminaires, light pipes, and shading devices.
50	greg	1.1	.PP
51	greg	1.2	.I Rtcontrib
52			calls
53			.I rtrace(1)
54	greg	1.5	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 files according to the given
57	greg	1.1	.I \-o
58			specification.
59	greg	1.2	If an output specification contains a "%s" format, this will be
60	greg	1.1	replaced by the modifier name.
61			The
62			.I \-b
63			option may be used to further define
64	greg	1.2	a "bin number" within each object if finer resolution is needed, and
65			this will be applied to a "%d" format in the output file
66	greg	1.1	specification if present.
67	greg	1.3	The actual bin number is computed at run time based on ray direction
68			and surface intersection, as described below.
69	greg	1.1	The most recent
70			.I \-b
71			and
72			.I \-o
73	greg	1.2	options to the left of each
74	greg	1.1	.I \-m
75	greg	1.2	setting affect only that modifier.
76			(The ordering of other options is unimportant.)\0
77	greg	1.1	.PP
78	greg	1.2	If a
79			.I \-b
80			expression is defined for a particular modifier,
81			the bin number will be evaluated at run time for each
82			ray contribution from
83			.I rtrace.
84			Specifically, each ray's world intersection point will be assigned to
85			the variables Px, Py, and Pz, and the normalized ray direction
86			will be assigned to Dx, Dy, and Dz.
87			These parameters may be combined with definitions given in
88			.I \-e
89	greg	1.3	arguments and files read using the
90	greg	1.2	.I \-f
91	greg	1.3	option.
92			The computed bin value will be
93	greg	1.2	rounded to the nearest whole number.
94			This mechanism allows the user to define precise regions or directions
95			they wish to accumulate, such as the Tregenza sky discretization,
96			which would be otherwise impossible to specify
97			as a set of RADIANCE primitives.
98	greg	1.3	The rules and predefined functions available for these expressions are
99			described in the
100			.I rcalc(1)
101			man page.
102	greg	1.6	Unlike
103			.I rcalc,
104			.I rtcontrib
105			will search the RADIANCE library directories for each file given in a
106			.I \-f
107			option.
108			(No search takes place if a file name begins with a '.', '/' or '~'
109			character.)\0
110	greg	1.1	.PP
111			If no
112			.I \-o
113			specification is given, results are written on the standard output in order
114			of modifier (as given on the command line) then bin number.
115	greg	1.2	Concatenated data is also sent to a lone output file (i.e., an initial
116			.I \-o
117			specification without formatting strings).
118	greg	1.1	If a "%s" format appears but no "%d" in the
119			.I \-o
120			specification, then each modifier will have its own output file, with
121			multiple values per record in the case of a non-zero
122			.I \-b
123			definition.
124			If a "%d" format appears but no "%s", then each bin will get its own
125			output file, with modifiers output in order in each record.
126			For text output, each RGB coefficient triple is separated by a tab,
127			with a newline at the end of each ray record.
128			For binary output formats, there is no such delimiter to mark
129			the end of each record.
130			.PP
131	greg	1.2	Input and output format defaults to plain text, where each ray's
132			origin and direction (6 real values) are given on input,
133			and one line is produced per output file per ray.
134			Alternative data representations may be specified by the
135			.I \-f[io]
136			option, which is described in the
137			.I rtrace
138			man page along with the associated
139			.I \-x
140			and
141			.I \-y
142			resolution settings.
143			In particular, the color ('c') output data representation
144			together with positive dimensions for
145			.I \-x
146			and
147			.I \-y
148			will produce an uncompressed RADIANCE picture,
149			suitable for manipulation with
150			.I pcomb(1)
151			and related tools.
152	greg	1.1	.PP
153			If the
154			.I \-n
155			option is specified with a value greater than 1, multiple
156	greg	1.2	.I rtrace
157	greg	1.1	processes will be used to accelerate computation on a shared
158			memory machine.
159			Note that there is no benefit to using more processes
160	greg	1.2	than there are local CPUs available to do the work, and the
161			.I rtcontrib
162			process itself may use a considerable amount of CPU time.
163	greg	1.1	.PP
164			Options may be given on the command line and/or read from the
165			environment and/or read from a file.
166			A command argument beginning with a dollar sign ('$') is immediately
167			replaced by the contents of the given environment variable.
168			A command argument beginning with an at sign ('@') is immediately
169			replaced by the contents of the given file.
170	greg	1.2	.SH EXAMPLES
171			To compute the proportional contributions from sources modified
172			by "light1" vs. "light2" on a set of illuminance values:
173	greg	1.1	.IP "" .2i
174	greg	1.2	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
175			.PP
176			To generate a pair of images corresponding to these two lights'
177			contributions:
178	greg	1.1	.IP "" .2i
179	greg	1.2	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
180			rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
181			@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
182			.PP
183			These images may then be recombined using the desired outputs
184			of light1 and light2:
185	greg	1.1	.IP "" .2i
186	greg	1.2	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
187	greg	1.1	.PP
188	greg	1.2	To compute an array of illuminance contributions according to a Tregenza sky:
189			.IP "" .2i
190			rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
191			@render.opt -f tregenza.cal scene.oct < test.dat
192	greg	1.6	.SH ENVIRONMENT
193			RAYPATH path to search for -f files
194	greg	1.1	.SH AUTHOR
195			Greg Ward
196			.SH "SEE ALSO"
197			cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
198			rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)