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
#	User	Rev	Content
1	greg	1.12	.\" RCSid "$Id: pcomb.1,v 1.11 2018/05/04 23:56:49 greg Exp $"
2	greg	1.1	.TH PCOMB 1 8/31/96 RADIANCE
3			.SH NAME
4	greg	1.2	pcomb - combine RADIANCE pictures
5	greg	1.1	.SH SYNOPSIS
6			.B pcomb
7			[
8	greg	1.7	.B -h
9			][
10	greg	1.1	.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	greg	1.11	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	greg	1.1	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	greg	1.6	y offsets are limited to a small window (+/- 32 pixels) due to efficiency
77	greg	1.1	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	greg	1.3	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	greg	1.1	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	greg	1.12	Exposure values will be set to 1.0 for inputs with the
122			.I \-o
123			option set.
124	greg	1.1	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	greg	1.10	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	greg	1.1	.PP
152			The
153	greg	1.7	.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	greg	1.1	.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	greg	1.8	pcomb \-e 'ro=ri(1)\-ri(2);go=gi(1)\-gi(2);bo=bi(1)\-bi(2)' pic1 pic2 > diff
210	greg	1.1	.PP
211			Or, more efficiently:
212			.IP "" .2i
213	greg	1.8	pcomb pic1 \-s \-1 pic2 > diff
214	greg	1.1	.PP
215			To precompute the gamma correction for a picture:
216			.IP "" .2i
217	greg	1.9	pcomb \-e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' inp.hdr > gam.hdr
218	greg	1.1	.PP
219			To perform some special filtering:
220			.IP "" .2i
221	greg	1.9	pcomb \-f myfilt.cal \-x xmax/2 \-y ymax/2 input.hdr > filtered.hdr
222	greg	1.1	.PP
223			To make a picture of a dot:
224			.IP "" .2i
225	greg	1.8	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	greg	1.11	.SH ENVIRONMENT
227			RAYPATH the directories to check for auxiliary files.
228	greg	1.1	.SH AUTHOR
229			Greg Ward
230			.SH "SEE ALSO"
231	greg	1.5	getinfo(1), icalc(1), pcompos(1), pfilt(1), rpict(1)