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Revision 1.18 by greg, Fri Apr 18 18:06:29 2008 UTC

#	Line 1 | Line 1
1		.\" RCSid "$Id$"
2	<	.TH RPIECE 1 5/25/05 RADIANCE
2	>	.TH RTCONTRIB 1 5/25/05 RADIANCE
3		.SH NAME
4	<	rtcontrib - compute contributions in a RADIANCE scene
4	>	rtcontrib - compute contribution coefficients in a RADIANCE scene
5		.SH SYNOPSIS
6		.B rtcontrib
7		[
8		.B "\-n nprocs"
9		][
10	+	.B \-V
11	+	][
12	+	.B "\-c count"
13	+	][
14	+	.B \-fo
15	+	|
16	+	.B \-r
17	+	][
18		.B "\-e expr"
19		][
20		.B "\-f source"
21		][
22	<	.B "\-o fspec"
22	>	.B "\-o ospec"
23		][
24		.B "\-b binv"
25	+	][
26	+	.B "\-bn nbins"
27		]
28	+	{
29	+	.B "\-m mod | \-M file"
30	+	}
31	+	..
32		[
33		.B $EVAR
34		]
#	Line 24 | Line 38 | rtcontrib - compute contributions in a RADIANCE scene
38		[
39		rtrace options
40		]
27	–	.B "\-m mod .."
41		.B octree
42	+	.br
43	+	.B "rtcontrib [ options ] \-defaults"
44		.SH DESCRIPTION
45		.I Rtcontrib
46	<	computes ray contributions (i.e., color coefficients)
46	>	computes ray coefficients
47		for objects whose modifiers are named in one or more
48		.I \-m
49		settings.
50	<	These modifiers are usually materials associated with specific
51	<	light sources, though they could correspond to intermediate objects as well.
52	<	The resulting contributions may then be used in linear combination to
50	>	These modifiers are usually materials associated with
51	>	light sources or sky domes, and must directly modify some geometric
52	>	primitives to be considered in the output.
53	>	A modifier list may also be read from a file using the
54	>	.I \-M
55	>	option.
56	>	The RAYPATH environment variable determines directories to search for
57	>	this file.
58	>	(No search takes place if a file name begins with a '.', '/' or '~'
59	>	character.)\0
60	>	.PP
61	>	If the
62	>	.I \-n
63	>	option is specified with a value greater than 1, multiple
64	>	.I rtrace
65	>	processes will be used to accelerate computation on a shared
66	>	memory machine.
67	>	Note that there is no benefit to using more processes
68	>	than there are local CPUs available to do the work, and the
69	>	.I rtcontrib
70	>	process itself may use a considerable amount of CPU time.
71	>	.PP
72	>	By setting the boolean
73	>	.I \-V
74	>	option, you may instruct
75	>	.I rtcontrib
76	>	to report the contribution from each material rather than the ray
77	>	coefficient.
78	>	This is particularly useful for light sources with directional output
79	>	distributions, whose value would otherwise be lost in the shuffle.
80	>	With the default
81	>	.I -V-
82	>	setting, the output of rtcontrib is a coefficient that must be multiplied
83	>	by the radiance of each material to arrive at a final contribution.
84	>	This is more convenient for computing daylight coefficeints, or cases
85	>	where the actual radiance is not desired.
86	>	Use the
87	>	.I -V+
88	>	setting when you wish to simply sum together contributions
89	>	(with possible adjustment factors) to obtain a final radiance value.
90	>	Combined with the
91	>	.I \-i
92	>	or
93	>	.I \-I
94	>	option, irradiance contributions are reported by
95	>	.I \-V+
96	>	rather than radiance, and
97	>	.I \-V-
98	>	coefficients contain an additonal factor of PI.
99	>	.PP
100	>	The
101	>	.I \-c
102	>	option tells
103	>	.I rtcontrib
104	>	how many rays to accumulate for each record.
105	>	The default value is 1, meaning a full record will be produced for
106	>	each input ray.
107	>	For values greater than 1, contributions will be averaged together
108	>	over the given number of input rays.
109	>	If set to zero, only a single record will be produced at the very
110	>	end, corresponding to the sum of all rays given on the input
111	>	(rather than the average).
112	>	This is equivalent to passing all the output records through a program like
113	>	.I total(1)
114	>	to sum RGB values together, but is much more efficient.
115	>	Using this option, it is possible to reverse sampling, sending rays from
116	>	a parallel source such as the sun to a diffuse surface, for example.
117	>	Note that output flushing via zero-direction rays is disabled
118	>	for accumulated evaluations.
119	>	.PP
120	>	The output of
121	>	.I rtcontrib
122	>	has many potential uses.
123	>	Source contributions can be used as components in linear combination to
124		reproduce any desired variation, e.g., simulating lighting controls or
125		changing sky conditions via daylight coefficients.
126		More generally,
127		.I rtcontrib
128	<	can compute general input-output relationships in optical
129	<	systems, such as light pipes and shading devices.
128	>	can be used to compute arbitrary input-output relationships in optical
129	>	systems, such as luminaires, light pipes, and shading devices.
130		.PP
131	<	.I Rtrace(1)
132	<	is called to calculate the contributions for each input ray,
133	<	and the output tallies are sent to one or more files according to the
131	>	.I Rtcontrib
132	>	calls
133	>	.I rtrace(1)
134	>	with the \-oTW (or \-oTV) option to calculate the daughter ray
135	>	contributions for each input ray, and the output tallies
136	>	are sent to one or more destinations according to the given
137		.I \-o
138		specification.
139	<	If the output file specification contains a "%s" format, this will be
139	>	If a destination begins with an exclamation mark ('!'), then
140	>	a pipe is opened to a command and data is sent to its standard input.
141	>	Otherwise, the destination is treated as a file.
142	>	An existing file of the same name will not be clobbered, unless the
143	>	.I \-fo
144	>	option is given.
145	>	If instead the
146	>	.I \-r
147	>	option is specified, data recovery is attempted on existing files.
148	>	(If
149	>	.I "\-c 0"
150	>	is used together with the
151	>	.I \-r
152	>	option, existing files are read in and new ray evaluations are added
153	>	to the previous results, providing a convenient means for
154	>	progressive simulation.)\0
155	>	If an output specification contains a "%s" format, this will be
156		replaced by the modifier name.
157		The
158		.I \-b
159		option may be used to further define
160	<	a "bin number" within each object if finer resolution is desired, and
161	<	will be applied to a "%d" format in the output file
160	>	a "bin number" within each object if finer resolution is needed, and
161	>	this will be applied to a "%d" format in the output file
162		specification if present.
163	<	(The actual bin number is computed at run time based on ray direction
164	<	and surface intersection, as described below.)\0
163	>	The actual bin number is computed at run time based on ray direction
164	>	and surface intersection, as described below.
165	>	If the number of bins is known in advance, it should be specified with the
166	>	.I \-bn
167	>	option, and this is critical for output files containing multiple values
168	>	per record.
169	>	Since bin numbers start from 0, the bin count is always equal to
170	>	the last bin plus 1.
171	>	Set the this value to 0 if the bin count is unknown (the default).
172		The most recent
173	<	.I \-b
173	>	.I \-b,
174	>	.I \-bn
175		and
176		.I \-o
177	<	options (to the left) of each
177	>	options to the left of each
178		.I \-m
179	<	setting affect only that modifier, and the ordering
180	<	of other options is unimportant.
68	<	.PP
69	<	Input and output format defaults to plain text, where each ray's
70	<	origin and direction (6 real values) must appear together per
71	<	line of input, and one line of output is produced per output file
72	<	file per ray.
73	<	Alternative input and output formats may be specified using the
74	<	.I \-f[io]
75	<	option, which is explained in the
76	<	.I rtrace
77	<	man page along with the associated
179	>	setting affect only that modifier.
180	>	The ordering of other options is unimportant, except for
181		.I \-x
182		and
183		.I \-y
184	<	resolution settings.
185	<	In particular, the 'c' output setting
186	<	together with positive dimensions for
187	<	.I \-x
85	<	and
86	<	.I \-y
87	<	will produce an uncompressed RADIANCE picture,
88	<	suitable for manipulation with
89	<	.I pcomb(1)
90	<	and related tools.
184	>	if the
185	>	.I \-c
186	>	is present, when they control the resolution string
187	>	produced in the corresponding output.
188		.PP
189	+	If a
190	+	.I \-b
191	+	expression is defined for a particular modifier,
192	+	the bin number will be evaluated at run time for each
193	+	ray contribution from
194	+	.I rtrace.
195	+	Specifically, each ray's world intersection point will be assigned to
196	+	the variables Px, Py, and Pz, and the normalized ray direction
197	+	will be assigned to Dx, Dy, and Dz.
198	+	These parameters may be combined with definitions given in
199	+	.I \-e
200	+	arguments and files read using the
201	+	.I \-f
202	+	option.
203	+	The computed bin value will be
204	+	rounded to the nearest whole number.
205	+	This mechanism allows the user to define precise regions or directions
206	+	they wish to accumulate, such as the Tregenza sky discretization,
207	+	which would be otherwise impossible to specify
208	+	as a set of RADIANCE primitives.
209	+	The rules and predefined functions available for these expressions are
210	+	described in the
211	+	.I rcalc(1)
212	+	man page.
213	+	Unlike
214	+	.I rcalc,
215	+	.I rtcontrib
216	+	will search the RADIANCE library directories for each file given in a
217	+	.I \-f
218	+	option.
219	+	.PP
220		If no
221		.I \-o
222		specification is given, results are written on the standard output in order
223		of modifier (as given on the command line) then bin number.
224	<	The same format is used for a simple file name specification
225	<	without any embedded "%s" or "%d" formats.
224	>	Concatenated data is also sent to a single destination (i.e., an initial
225	>	.I \-o
226	>	specification without formatting strings).
227		If a "%s" format appears but no "%d" in the
228		.I \-o
229		specification, then each modifier will have its own output file, with
#	Line 108 | Line 237 | with a newline at the end of each ray record.
237		For binary output formats, there is no such delimiter to mark
238		the end of each record.
239		.PP
240	<	If a
241	<	.I \-b
242	<	expression is defined for a particular modifier,
243	<	the bin number will be evaluated at run time for each
244	<	ray contribution from
245	<	.I rtrace.
246	<	Specifically, each ray's world intersection point will be assigned to
247	<	the variables Px, Py, and Pz, and the normalized ray direction
248	<	will be assigned to Dx, Dy, and Dz.
249	<	These ray parameters may be combined with any definitions given in
250	<	.I \-e
251	<	options, or any files read in from
252	<	.I \-f
253	<	options, to compute the bin, which will be
254	<	rounded to the closest whole number.
255	<	This mechanism allows the user to define precise regions (or directions)
256	<	they wish to accumulate, such as the Tregenza sky grid, which would be
257	<	otherwise impossible to specify as a set of RADIANCE primitives.
240	>	Input and output format defaults to plain text, where each ray's
241	>	origin and direction (6 real values) are given on input,
242	>	and one line is produced per output file per ray.
243	>	Alternative data representations may be specified by the
244	>	.I \-f[io]
245	>	option, which is described in the
246	>	.I rtrace
247	>	man page along with the associated
248	>	.I \-x
249	>	and
250	>	.I \-y
251	>	resolution settings.
252	>	In particular, the color ('c') output data representation
253	>	together with positive dimensions for
254	>	.I \-x
255	>	and
256	>	.I \-y
257	>	will produce an uncompressed RADIANCE picture,
258	>	suitable for manipulation with
259	>	.I pcomb(1)
260	>	and related tools.
261		.PP
130	–	If the
131	–	.I \-n
132	–	option is specified with a value greater than 1, multiple
133	–	.I rtrace(1)
134	–	processes will be used to accelerate computation on a shared
135	–	memory machine.
136	–	Note that there is no benefit to using more processes
137	–	than there are local CPUs available to do the work.
138	–	.PP
262		Options may be given on the command line and/or read from the
263		environment and/or read from a file.
264		A command argument beginning with a dollar sign ('$') is immediately
265		replaced by the contents of the given environment variable.
266		A command argument beginning with an at sign ('@') is immediately
267		replaced by the contents of the given file.
268	<	.SH EXAMPLE
269	<	First
270	<	.I rpiece
148	<	process is started on the machine "goober":
268	>	.SH EXAMPLES
269	>	To compute the proportional contributions from sources modified
270	>	by "light1" vs. "light2" on a set of illuminance values:
271		.IP "" .2i
272	<	goober% echo 1 8 > syncfile
151	<	.br
152	<	goober% echo -F syncfile -x 1024 -y 1024 -vf view -o picture octree > args
153	<	.br
154	<	goober% rpiece @args &
272	>	rtcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat
273		.PP
274	<	Second
275	<	.I rpiece
158	<	processes is started on the machine "sucker":
274	>	To generate a pair of images corresponding to these two lights'
275	>	contributions:
276		.IP "" .2i
277	<	sucker% rpiece @args &
278	<	.SH NOTES
279	<	Due to NFS file buffering, the network lock manager is employed to
163	<	guarantee consistency in the output file even though non-overlapping
164	<	writes are used.
165	<	This would tend to slow the process down if
166	<	.I rpiece
167	<	were to wait for this I/O to complete before starting on the next
168	<	piece, so
169	<	.I rpiece
170	<	forks separate processes to hang around waiting for I/O completion.
171	<	The number of processes thus designated is set by the MAXFORK macro
172	<	in the program (compiled in the src/util directory).
173	<	If the fork call is slow on a system, it may actually be better to
174	<	set MAXFORK to zero.
175	<	In other cases, the network lock manager may be so slow that this
176	<	value should be increased to get the best utilization.
277	>	vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf |
278	>	rtcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf`
279	>	@render.opt \-o c_%s.pic \-m light1 \-m light2 scene.oct
280		.PP
281	<	The output picture is not run-length encoded, and can be quite
282	<	large.
180	<	The approximate size (in kilobytes) can be computed by the simple
181	<	formula:
281	>	These images may then be recombined using the desired outputs
282	>	of light1 and light2:
283		.IP "" .2i
284	<	filesize = xres*yres/256
284	>	pcomb \-c 100 90 75 c_light1.pic \-c 50 55 57 c_light2.pic > combined.pic
285		.PP
286	<	Make sure that there is enough space on the filesystem to hold the
287	<	entire picture before beginning.
288	<	Once the picture is finished, the
289	<	.I ra_rgbe(1)
290	<	program with the -r option may be used to convert to a run-length
291	<	encoded picture for more efficient storage, although
191	<	.I pfilt(1)
192	<	or any of the other Radiance picture filters will do the same
193	<	thing.
194	<	.PP
195	<	The ALRM signal may be used to gracefully terminate an
196	<	.I rpiece
197	<	process after it finishes the current piece.
198	<	This permits other currently running or subsequently started
199	<	.I rpiece
200	<	process(es) to continue rendering the picture without loss.
201	<	The
202	<	.I \-T
203	<	option will send the ALRM signal to
204	<	.I rpiece
205	<	after the specified number of (decimal) hours.
206	<	This is the best way to force a time limit on the computation,
207	<	since information will not be lost, though the process may continue
208	<	for some time afterwards to finish its current piece.
209	<	.SH BUGS
210	<	This program may not work on some systems whose NFS lock manager is
211	<	unreliable.
212	<	In particular, some System V derivative UNIX systems often have
213	<	problems with the network lock manager.
214	<	If the output is scrambled or rpict aborts with some ambient file
215	<	related problem, you should just remove the ambient file and go
216	<	back to normal rendering.
286	>	To compute an array of illuminance contributions according to a Tregenza sky:
287	>	.IP "" .2i
288	>	rtcontrib \-I+ \-b tbin \-o sky.dat \-m skyglow \-b 0 \-o ground.dat \-m groundglow
289	>	@render.opt \-f tregenza.cal scene.oct < test.dat
290	>	.SH ENVIRONMENT
291	>	RAYPATH         path to search for \-f and \-M files
292		.SH AUTHOR
293		Greg Ward
294		.SH "SEE ALSO"
295		cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1),
296	<	rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1)
296	>	rcalc(1), rpict(1), rtrace(1), total(1), vwrays(1), ximage(1)

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