man/man1/pcomb.1

.\" RCSid "$Id: pcomb.1,v 1.12 2022/03/18 21:09:16 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.)\0
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), rmtxcomb(1), rmtxop(1), rpict(1)
Revision:	1.13
Committed:	Wed Dec 6 01:27:00 2023 UTC (5 months, 4 weeks ago) by greg
Branch:	MAIN
Changes since 1.12:	+5 -4 lines
Log Message:	docs(rmtxcomb): Added man page for new rmtxcomb tool
#	User	Rev	Content
1	greg	1.13	.\" RCSid "$Id: pcomb.1,v 1.12 2022/03/18 21:09:16 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	1.13	(The variable and function definitions in each
46	greg	1.11	.I \-f source
47	greg	1.13	file are read and compiled from the RADIANCE library
48			where it is found.)\0
49	greg	1.1	Negative coefficients and functions are allowed, and
50			.I pcomb
51			will produce color values of zero where they would be negative.
52			.PP
53			The variables
54			.I ro,
55			.I go
56			and
57			.I bo
58			specify the red, green and blue output values, respectively.
59			Alternatively, the single variable
60			.I lo
61			can be used to specify a brightness value for black and white output.
62			The predefined functions
63			.I ri(n),
64			.I gi(n)
65			and
66			.I bi(n)
67			give the red, green and blue input values for
68			picture
69			.I n.
70			To access a pixel that is nearby the current one, these functions
71			also accept optional x and y offsets.
72			For example,
73			.I ri(3,-2,1)
74			would return the red component of the pixel from picture 3
75			that is left 2 and up 1 from the current position.
76			Although x offsets may be as large as width of the picture,
77	greg	1.6	y offsets are limited to a small window (+/- 32 pixels) due to efficiency
78	greg	1.1	considerations.
79			However, it is not usually necessary to worry about this problem --
80			if the requested offset is not available, the next best pixel is
81			returned instead.
82			.PP
83			For additional convenience, the function
84			.I li(n)
85			is defined as the input brightness for picture
86			.I n.
87			This function also accepts x and y offsets.
88			.PP
89			The constant
90			.I nfiles
91			gives the number of input files present,
92			and
93			.I WE
94	greg	1.3	gives the white efficacy (lumens/brightness) for pixel values,
95			which may be used with the
96			.I \-o
97			option or the le(n) values to convert to absolute
98			photometric units (see below).
99	greg	1.1	The variables
100			.I x
101			and
102			.I y
103			give the current output pixel location for use in
104			spatially dependent functions, the constants
105			.I xmax
106			and
107			.I ymax
108			give the input resolution, and the constants
109			.I xres
110			and
111			.I yres
112			give the output resolution (usually the same, but see below).
113			The constant functions
114			.I "re(n), ge(n), be(n),"
115			and
116			.I le(n)
117			give the exposure values for picture
118			.I n,
119			and
120			.I pa(n)
121			gives the corresponding pixel aspect ratio.
122	greg	1.12	Exposure values will be set to 1.0 for inputs with the
123			.I \-o
124			option set.
125	greg	1.1	Finally, for pictures with stored view parameters,
126			the functions
127			.I "Ox(n), Oy(n)"
128			and
129			.I Oz(n)
130			return the ray origin in world coordinates for the current pixel
131			in picture
132			.I n,
133			and
134			.I "Dx(n), Dy(n)"
135			and
136			.I Dz(n)
137			return the normalized ray direction.
138			In addition, the function
139			.I T(n)
140			returns the distance from the origin to the aft clipping plane
141			(or zero if there is no aft plane), and the function
142			.I S(n)
143			returns the solid angle of the current pixel in steradians
144			(always zero for parallel views).
145			If the current pixel is outside the view region,
146			.I T(n)
147			will return a negative value, and
148			.I S(n)
149			will return zero.
150	greg	1.10	The first input picture with a view is assumed to correspond to the
151			view of the output picture, which is written into the header.
152	greg	1.1	.PP
153			The
154	greg	1.7	.I \-h
155			option may be used to reduce the information header size, which
156			can grow disproportionately after multiple runs of
157			.I pcomb
158			and/or
159			.I pcompos(1).
160			The
161	greg	1.1	.I \-w
162			option can be used to suppress warning messages about invalid
163			calculations.
164			The
165			.I \-o
166			option indicates that original pixel values are to be used for the next
167			picture, undoing any previous exposure changes or color correction.
168			.PP
169			The
170			.I \-x
171			and
172			.I \-y
173			options can be used to specify the desired output resolution,
174			.I xres
175			and
176			.I yres,
177			and can be expressions involving other constants such as
178			.I xmax
179			and
180			.I ymax.
181			The constants
182			.I xres
183			and
184			.I yres
185			may also be specified in a file or expression.
186			The default output resolution is the same as the input resolution.
187			.PP
188			The
189			.I \-x
190			and
191			.I \-y
192			options must be present if there are no input files, when
193			the definitions of
194			.I ro,
195			.I go
196			and
197			.I bo
198			will be used to compute each output pixel.
199			This is useful for producing simple test pictures for various
200			purposes.
201			(Theoretically, one could write a complete renderer using just the
202			functional language...)
203			.PP
204			The standard input can be specified with a hyphen ('-').
205			A command that produces a RADIANCE picture can be given in place of a file
206			by preceeding it with an exclamation point ('!').
207			.SH EXAMPLES
208			To produce a picture showing the difference between pic1 and pic2:
209			.IP "" .2i
210	greg	1.8	pcomb \-e 'ro=ri(1)\-ri(2);go=gi(1)\-gi(2);bo=bi(1)\-bi(2)' pic1 pic2 > diff
211	greg	1.1	.PP
212			Or, more efficiently:
213			.IP "" .2i
214	greg	1.8	pcomb pic1 \-s \-1 pic2 > diff
215	greg	1.1	.PP
216			To precompute the gamma correction for a picture:
217			.IP "" .2i
218	greg	1.9	pcomb \-e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' inp.hdr > gam.hdr
219	greg	1.1	.PP
220			To perform some special filtering:
221			.IP "" .2i
222	greg	1.9	pcomb \-f myfilt.cal \-x xmax/2 \-y ymax/2 input.hdr > filtered.hdr
223	greg	1.1	.PP
224			To make a picture of a dot:
225			.IP "" .2i
226	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
227	greg	1.11	.SH ENVIRONMENT
228			RAYPATH the directories to check for auxiliary files.
229	greg	1.1	.SH AUTHOR
230			Greg Ward
231			.SH "SEE ALSO"
232	greg	1.13	getinfo(1), icalc(1), pcompos(1), pfilt(1), rmtxcomb(1), rmtxop(1), rpict(1)