man/man1/rtcontrib.1

.\" RCSid "$Id: rtcontrib.1,v 1.4 2005/05/26 21:03:22 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.
.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 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:	1.5
Committed:	Fri May 27 19:15:28 2005 UTC (18 years, 11 months ago) by greg
Branch:	MAIN
Changes since 1.4:	+5 -4 lines
Log Message:	Wording tweaks
#	User	Rev	Content
1	greg	1.5	.\" RCSid "$Id: rtcontrib.1,v 1.4 2005/05/26 21:03:22 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	1.1	.PP
103			If no
104			.I \-o
105			specification is given, results are written on the standard output in order
106			of modifier (as given on the command line) then bin number.
107	greg	1.2	Concatenated data is also sent to a lone output file (i.e., an initial
108			.I \-o
109			specification without formatting strings).
110	greg	1.1	If a "%s" format appears but no "%d" in the
111			.I \-o
112			specification, then each modifier will have its own output file, with
113			multiple values per record in the case of a non-zero
114			.I \-b
115			definition.
116			If a "%d" format appears but no "%s", then each bin will get its own
117			output file, with modifiers output in order in each record.
118			For text output, each RGB coefficient triple is separated by a tab,
119			with a newline at the end of each ray record.
120			For binary output formats, there is no such delimiter to mark
121			the end of each record.
122			.PP
123	greg	1.2	Input and output format defaults to plain text, where each ray's
124			origin and direction (6 real values) are given on input,
125			and one line is produced per output file per ray.
126			Alternative data representations may be specified by the
127			.I \-f[io]
128			option, which is described in the
129			.I rtrace
130			man page along with the associated
131			.I \-x
132			and
133			.I \-y
134			resolution settings.
135			In particular, the color ('c') output data representation
136			together with positive dimensions for
137			.I \-x
138			and
139			.I \-y
140			will produce an uncompressed RADIANCE picture,
141			suitable for manipulation with
142			.I pcomb(1)
143			and related tools.
144	greg	1.1	.PP
145			If the
146			.I \-n
147			option is specified with a value greater than 1, multiple
148	greg	1.2	.I rtrace
149	greg	1.1	processes will be used to accelerate computation on a shared
150			memory machine.
151			Note that there is no benefit to using more processes
152	greg	1.2	than there are local CPUs available to do the work, and the
153			.I rtcontrib
154			process itself may use a considerable amount of CPU time.
155	greg	1.1	.PP
156			Options may be given on the command line and/or read from the
157			environment and/or read from a file.
158			A command argument beginning with a dollar sign ('$') is immediately
159			replaced by the contents of the given environment variable.
160			A command argument beginning with an at sign ('@') is immediately
161			replaced by the contents of the given file.
162	greg	1.2	.SH EXAMPLES
163			To compute the proportional contributions from sources modified
164			by "light1" vs. "light2" on a set of illuminance values:
165	greg	1.1	.IP "" .2i
166	greg	1.2	rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat
167			.PP
168			To generate a pair of images corresponding to these two lights'
169			contributions:
170	greg	1.1	.IP "" .2i
171	greg	1.2	vwrays -ff -x 1024 -y 1024 -vf best.vf \|
172			rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf`
173			@render.opt -o c_%s.pic -m light1 -m light2 scene.oct
174			.PP
175			These images may then be recombined using the desired outputs
176			of light1 and light2:
177	greg	1.1	.IP "" .2i
178	greg	1.2	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
179	greg	1.1	.PP
180	greg	1.2	To compute an array of illuminance contributions according to a Tregenza sky:
181			.IP "" .2i
182			rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow
183			@render.opt -f tregenza.cal scene.oct < test.dat
184	greg	1.1	.SH AUTHOR
185			Greg Ward
186			.SH "SEE ALSO"
187			cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
188			rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)