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 (19 years ago) by greg
Branch:	MAIN
Changes since 1.4:	+5 -4 lines
Log Message:	Wording tweaks
#	Content
1	.\" RCSid "$Id: rtcontrib.1,v 1.4 2005/05/26 21:03:22 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 fspec"
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 files according to the given
57	.I \-o
58	specification.
59	If an output specification contains a "%s" format, this will be
60	replaced by the modifier name.
61	The
62	.I \-b
63	option may be used to further define
64	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	specification if present.
67	The actual bin number is computed at run time based on ray direction
68	and surface intersection, as described below.
69	The most recent
70	.I \-b
71	and
72	.I \-o
73	options to the left of each
74	.I \-m
75	setting affect only that modifier.
76	(The ordering of other options is unimportant.)\0
77	.PP
78	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	arguments and files read using the
90	.I \-f
91	option.
92	The computed bin value will be
93	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	The rules and predefined functions available for these expressions are
99	described in the
100	.I rcalc(1)
101	man page.
102	.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	Concatenated data is also sent to a lone output file (i.e., an initial
108	.I \-o
109	specification without formatting strings).
110	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	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	.PP
145	If the
146	.I \-n
147	option is specified with a value greater than 1, multiple
148	.I rtrace
149	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	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	.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	.SH EXAMPLES
163	To compute the proportional contributions from sources modified
164	by "light1" vs. "light2" on a set of illuminance values:
165	.IP "" .2i
166	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	.IP "" .2i
171	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	.IP "" .2i
178	pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic
179	.PP
180	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	.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)