man/man1/pcomb.1

.\" RCSid "$Id: pcomb.1,v 1.11 2018/05/04 23:56:49 greg Exp $"
.TH PCOMB 1 8/31/96 RADIANCE
.SH NAME
pcomb - combine RADIANCE pictures
.SH SYNOPSIS
.B pcomb
[
.B -h
][
.B -w
][
.B "\-x xres"
][
.B "\-y yres"
][
.B "\-f file"
][
.B "\-e expr"
]
[
[
.B -o
][
.B "\-s factor"
][
.B "\-c r g b"
]
.B "input .."
]
.SH DESCRIPTION
.I Pcomb
combines equal-sized RADIANCE pictures and sends the result to the
standard output.
By default, the result is just a linear combination of
the input pictures multiplied by
.I \-s
and
.I \-c
coefficients,
but an arbitrary mapping can be assigned with the
.I \-e
and
.I \-f
options.
The variable and function definitions in each
.I \-f source
file are read and compiled from the RADIANCE library where it is found.
Negative coefficients and functions are allowed, and
.I pcomb
will produce color values of zero where they would be negative.
.PP
The variables
.I ro,
.I go
and
.I bo
specify the red, green and blue output values, respectively.
Alternatively, the single variable
.I lo
can be used to specify a brightness value for black and white output.
The predefined functions
.I ri(n),
.I gi(n)
and
.I bi(n)
give the red, green and blue input values for
picture
.I n.
To access a pixel that is nearby the current one, these functions
also accept optional x and y offsets.
For example,
.I ri(3,-2,1)
would return the red component of the pixel from picture 3
that is left 2 and up 1 from the current position.
Although x offsets may be as large as width of the picture,
y offsets are limited to a small window (+/- 32 pixels) due to efficiency
considerations.
However, it is not usually necessary to worry about this problem --
if the requested offset is not available, the next best pixel is
returned instead.
.PP
For additional convenience, the function
.I li(n)
is defined as the input brightness for picture
.I n.
This function also accepts x and y offsets.
.PP
The constant
.I nfiles
gives the number of input files present,
and
.I WE
gives the white efficacy (lumens/brightness) for pixel values,
which may be used with the
.I \-o
option or the le(n) values to convert to absolute
photometric units (see below).
The variables
.I x
and
.I y
give the current output pixel location for use in
spatially dependent functions, the constants
.I xmax
and
.I ymax
give the input resolution, and the constants
.I xres
and 
.I yres
give the output resolution (usually the same, but see below).
The constant functions
.I "re(n), ge(n), be(n),"
and
.I le(n)
give the exposure values for picture
.I n,
and
.I pa(n)
gives the corresponding pixel aspect ratio.
Exposure values will be set to 1.0 for inputs with the
.I \-o
option set.
Finally, for pictures with stored view parameters,
the functions
.I "Ox(n), Oy(n)"
and
.I Oz(n)
return the ray origin in world coordinates for the current pixel
in picture
.I n,
and
.I "Dx(n), Dy(n)"
and
.I Dz(n)
return the normalized ray direction.
In addition, the function
.I T(n)
returns the distance from the origin to the aft clipping plane
(or zero if there is no aft plane), and the function
.I S(n)
returns the solid angle of the current pixel in steradians
(always zero for parallel views).
If the current pixel is outside the view region,
.I T(n)
will return a negative value, and
.I S(n)
will return zero.
The first input picture with a view is assumed to correspond to the
view of the output picture, which is written into the header.
.PP
The
.I \-h
option may be used to reduce the information header size, which
can grow disproportionately after multiple runs of
.I pcomb
and/or
.I pcompos(1).
The
.I \-w
option can be used to suppress warning messages about invalid
calculations.
The
.I \-o
option indicates that original pixel values are to be used for the next
picture, undoing any previous exposure changes or color correction.
.PP
The
.I \-x
and
.I \-y
options can be used to specify the desired output resolution,
.I xres
and
.I yres,
and can be expressions involving other constants such as
.I xmax
and
.I ymax.
The constants
.I xres
and
.I yres
may also be specified in a file or expression.
The default output resolution is the same as the input resolution.
.PP
The
.I \-x
and
.I \-y
options must be present if there are no input files, when
the definitions of
.I ro,
.I go
and
.I bo
will be used to compute each output pixel.
This is useful for producing simple test pictures for various
purposes.
(Theoretically, one could write a complete renderer using just the
functional language...)
.PP
The standard input can be specified with a hyphen ('-').
A command that produces a RADIANCE picture can be given in place of a file 
by preceeding it with an exclamation point ('!').
.SH EXAMPLES
To produce a picture showing the difference between pic1 and pic2:
.IP "" .2i
pcomb \-e 'ro=ri(1)\-ri(2);go=gi(1)\-gi(2);bo=bi(1)\-bi(2)' pic1 pic2 > diff
.PP
Or, more efficiently:
.IP "" .2i
pcomb pic1 \-s \-1 pic2 > diff
.PP
To precompute the gamma correction for a picture:
.IP "" .2i
pcomb \-e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' inp.hdr > gam.hdr
.PP
To perform some special filtering:
.IP "" .2i
pcomb \-f myfilt.cal \-x xmax/2 \-y ymax/2 input.hdr > filtered.hdr
.PP
To make a picture of a dot:
.IP "" .2i
pcomb \-x 100 \-y 100 \-e 'ro=b;go=b;bo=b;b=if((x-50)^2+(y-50)^2\-25^2,0,1)' > dot
.SH ENVIRONMENT
RAYPATH         the directories to check for auxiliary files.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
getinfo(1), icalc(1), pcompos(1), pfilt(1), rpict(1)
Revision:	1.12
Committed:	Fri Mar 18 21:09:16 2022 UTC (2 years, 2 months ago) by greg
Branch:	MAIN
CVS Tags:	rad5R4
Changes since 1.11:	+4 -1 lines
Log Message:	docs(pcomb, pcompos): Added remarks about EXPOSURE settings
#	Content
1	.\" RCSid "$Id: pcomb.1,v 1.11 2018/05/04 23:56:49 greg Exp $"
2	.TH PCOMB 1 8/31/96 RADIANCE
3	.SH NAME
4	pcomb - combine RADIANCE pictures
5	.SH SYNOPSIS
6	.B pcomb
7	[
8	.B -h
9	][
10	.B -w
11	][
12	.B "\-x xres"
13	][
14	.B "\-y yres"
15	][
16	.B "\-f file"
17	][
18	.B "\-e expr"
19	]
20	[
21	[
22	.B -o
23	][
24	.B "\-s factor"
25	][
26	.B "\-c r g b"
27	]
28	.B "input .."
29	]
30	.SH DESCRIPTION
31	.I Pcomb
32	combines equal-sized RADIANCE pictures and sends the result to the
33	standard output.
34	By default, the result is just a linear combination of
35	the input pictures multiplied by
36	.I \-s
37	and
38	.I \-c
39	coefficients,
40	but an arbitrary mapping can be assigned with the
41	.I \-e
42	and
43	.I \-f
44	options.
45	The variable and function definitions in each
46	.I \-f source
47	file are read and compiled from the RADIANCE library where it is found.
48	Negative coefficients and functions are allowed, and
49	.I pcomb
50	will produce color values of zero where they would be negative.
51	.PP
52	The variables
53	.I ro,
54	.I go
55	and
56	.I bo
57	specify the red, green and blue output values, respectively.
58	Alternatively, the single variable
59	.I lo
60	can be used to specify a brightness value for black and white output.
61	The predefined functions
62	.I ri(n),
63	.I gi(n)
64	and
65	.I bi(n)
66	give the red, green and blue input values for
67	picture
68	.I n.
69	To access a pixel that is nearby the current one, these functions
70	also accept optional x and y offsets.
71	For example,
72	.I ri(3,-2,1)
73	would return the red component of the pixel from picture 3
74	that is left 2 and up 1 from the current position.
75	Although x offsets may be as large as width of the picture,
76	y offsets are limited to a small window (+/- 32 pixels) due to efficiency
77	considerations.
78	However, it is not usually necessary to worry about this problem --
79	if the requested offset is not available, the next best pixel is
80	returned instead.
81	.PP
82	For additional convenience, the function
83	.I li(n)
84	is defined as the input brightness for picture
85	.I n.
86	This function also accepts x and y offsets.
87	.PP
88	The constant
89	.I nfiles
90	gives the number of input files present,
91	and
92	.I WE
93	gives the white efficacy (lumens/brightness) for pixel values,
94	which may be used with the
95	.I \-o
96	option or the le(n) values to convert to absolute
97	photometric units (see below).
98	The variables
99	.I x
100	and
101	.I y
102	give the current output pixel location for use in
103	spatially dependent functions, the constants
104	.I xmax
105	and
106	.I ymax
107	give the input resolution, and the constants
108	.I xres
109	and
110	.I yres
111	give the output resolution (usually the same, but see below).
112	The constant functions
113	.I "re(n), ge(n), be(n),"
114	and
115	.I le(n)
116	give the exposure values for picture
117	.I n,
118	and
119	.I pa(n)
120	gives the corresponding pixel aspect ratio.
121	Exposure values will be set to 1.0 for inputs with the
122	.I \-o
123	option set.
124	Finally, for pictures with stored view parameters,
125	the functions
126	.I "Ox(n), Oy(n)"
127	and
128	.I Oz(n)
129	return the ray origin in world coordinates for the current pixel
130	in picture
131	.I n,
132	and
133	.I "Dx(n), Dy(n)"
134	and
135	.I Dz(n)
136	return the normalized ray direction.
137	In addition, the function
138	.I T(n)
139	returns the distance from the origin to the aft clipping plane
140	(or zero if there is no aft plane), and the function
141	.I S(n)
142	returns the solid angle of the current pixel in steradians
143	(always zero for parallel views).
144	If the current pixel is outside the view region,
145	.I T(n)
146	will return a negative value, and
147	.I S(n)
148	will return zero.
149	The first input picture with a view is assumed to correspond to the
150	view of the output picture, which is written into the header.
151	.PP
152	The
153	.I \-h
154	option may be used to reduce the information header size, which
155	can grow disproportionately after multiple runs of
156	.I pcomb
157	and/or
158	.I pcompos(1).
159	The
160	.I \-w
161	option can be used to suppress warning messages about invalid
162	calculations.
163	The
164	.I \-o
165	option indicates that original pixel values are to be used for the next
166	picture, undoing any previous exposure changes or color correction.
167	.PP
168	The
169	.I \-x
170	and
171	.I \-y
172	options can be used to specify the desired output resolution,
173	.I xres
174	and
175	.I yres,
176	and can be expressions involving other constants such as
177	.I xmax
178	and
179	.I ymax.
180	The constants
181	.I xres
182	and
183	.I yres
184	may also be specified in a file or expression.
185	The default output resolution is the same as the input resolution.
186	.PP
187	The
188	.I \-x
189	and
190	.I \-y
191	options must be present if there are no input files, when
192	the definitions of
193	.I ro,
194	.I go
195	and
196	.I bo
197	will be used to compute each output pixel.
198	This is useful for producing simple test pictures for various
199	purposes.
200	(Theoretically, one could write a complete renderer using just the
201	functional language...)
202	.PP
203	The standard input can be specified with a hyphen ('-').
204	A command that produces a RADIANCE picture can be given in place of a file
205	by preceeding it with an exclamation point ('!').
206	.SH EXAMPLES
207	To produce a picture showing the difference between pic1 and pic2:
208	.IP "" .2i
209	pcomb \-e 'ro=ri(1)\-ri(2);go=gi(1)\-gi(2);bo=bi(1)\-bi(2)' pic1 pic2 > diff
210	.PP
211	Or, more efficiently:
212	.IP "" .2i
213	pcomb pic1 \-s \-1 pic2 > diff
214	.PP
215	To precompute the gamma correction for a picture:
216	.IP "" .2i
217	pcomb \-e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' inp.hdr > gam.hdr
218	.PP
219	To perform some special filtering:
220	.IP "" .2i
221	pcomb \-f myfilt.cal \-x xmax/2 \-y ymax/2 input.hdr > filtered.hdr
222	.PP
223	To make a picture of a dot:
224	.IP "" .2i
225	pcomb \-x 100 \-y 100 \-e 'ro=b;go=b;bo=b;b=if((x-50)^2+(y-50)^2\-25^2,0,1)' > dot
226	.SH ENVIRONMENT
227	RAYPATH the directories to check for auxiliary files.
228	.SH AUTHOR
229	Greg Ward
230	.SH "SEE ALSO"
231	getinfo(1), icalc(1), pcompos(1), pfilt(1), rpict(1)