man/man1/pcomb.1

.\" RCSid "$Id: pcomb.1,v 1.13 2023/12/06 01:27:00 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, similar to
.I rcalc(1).
(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), rcalc(1),
rmtxcomb(1), rmtxop(1), rpict(1)
Revision:	1.14
Committed:	Wed Dec 6 17:56:57 2023 UTC (6 months ago) by greg
Branch:	MAIN
Changes since 1.13:	+5 -3 lines
Log Message:	docs(rmtxcomb): Added example and described -h option
#	Content
1	.\" RCSid "$Id: pcomb.1,v 1.13 2023/12/06 01:27:00 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, similar to
45	.I rcalc(1).
46	(The variable and function definitions in each
47	.I \-f source
48	file are read and compiled from the RADIANCE library
49	where it is found.)\0
50	Negative coefficients and functions are allowed, and
51	.I pcomb
52	will produce color values of zero where they would be negative.
53	.PP
54	The variables
55	.I ro,
56	.I go
57	and
58	.I bo
59	specify the red, green and blue output values, respectively.
60	Alternatively, the single variable
61	.I lo
62	can be used to specify a brightness value for black and white output.
63	The predefined functions
64	.I ri(n),
65	.I gi(n)
66	and
67	.I bi(n)
68	give the red, green and blue input values for
69	picture
70	.I n.
71	To access a pixel that is nearby the current one, these functions
72	also accept optional x and y offsets.
73	For example,
74	.I ri(3,-2,1)
75	would return the red component of the pixel from picture 3
76	that is left 2 and up 1 from the current position.
77	Although x offsets may be as large as width of the picture,
78	y offsets are limited to a small window (+/- 32 pixels) due to efficiency
79	considerations.
80	However, it is not usually necessary to worry about this problem --
81	if the requested offset is not available, the next best pixel is
82	returned instead.
83	.PP
84	For additional convenience, the function
85	.I li(n)
86	is defined as the input brightness for picture
87	.I n.
88	This function also accepts x and y offsets.
89	.PP
90	The constant
91	.I nfiles
92	gives the number of input files present,
93	and
94	.I WE
95	gives the white efficacy (lumens/brightness) for pixel values,
96	which may be used with the
97	.I \-o
98	option or the le(n) values to convert to absolute
99	photometric units (see below).
100	The variables
101	.I x
102	and
103	.I y
104	give the current output pixel location for use in
105	spatially dependent functions, the constants
106	.I xmax
107	and
108	.I ymax
109	give the input resolution, and the constants
110	.I xres
111	and
112	.I yres
113	give the output resolution (usually the same, but see below).
114	The constant functions
115	.I "re(n), ge(n), be(n),"
116	and
117	.I le(n)
118	give the exposure values for picture
119	.I n,
120	and
121	.I pa(n)
122	gives the corresponding pixel aspect ratio.
123	Exposure values will be set to 1.0 for inputs with the
124	.I \-o
125	option set.
126	Finally, for pictures with stored view parameters,
127	the functions
128	.I "Ox(n), Oy(n)"
129	and
130	.I Oz(n)
131	return the ray origin in world coordinates for the current pixel
132	in picture
133	.I n,
134	and
135	.I "Dx(n), Dy(n)"
136	and
137	.I Dz(n)
138	return the normalized ray direction.
139	In addition, the function
140	.I T(n)
141	returns the distance from the origin to the aft clipping plane
142	(or zero if there is no aft plane), and the function
143	.I S(n)
144	returns the solid angle of the current pixel in steradians
145	(always zero for parallel views).
146	If the current pixel is outside the view region,
147	.I T(n)
148	will return a negative value, and
149	.I S(n)
150	will return zero.
151	The first input picture with a view is assumed to correspond to the
152	view of the output picture, which is written into the header.
153	.PP
154	The
155	.I \-h
156	option may be used to reduce the information header size, which
157	can grow disproportionately after multiple runs of
158	.I pcomb
159	and/or
160	.I pcompos(1).
161	The
162	.I \-w
163	option can be used to suppress warning messages about invalid
164	calculations.
165	The
166	.I \-o
167	option indicates that original pixel values are to be used for the next
168	picture, undoing any previous exposure changes or color correction.
169	.PP
170	The
171	.I \-x
172	and
173	.I \-y
174	options can be used to specify the desired output resolution,
175	.I xres
176	and
177	.I yres,
178	and can be expressions involving other constants such as
179	.I xmax
180	and
181	.I ymax.
182	The constants
183	.I xres
184	and
185	.I yres
186	may also be specified in a file or expression.
187	The default output resolution is the same as the input resolution.
188	.PP
189	The
190	.I \-x
191	and
192	.I \-y
193	options must be present if there are no input files, when
194	the definitions of
195	.I ro,
196	.I go
197	and
198	.I bo
199	will be used to compute each output pixel.
200	This is useful for producing simple test pictures for various
201	purposes.
202	(Theoretically, one could write a complete renderer using just the
203	functional language...)
204	.PP
205	The standard input can be specified with a hyphen ('-').
206	A command that produces a RADIANCE picture can be given in place of a file
207	by preceeding it with an exclamation point ('!').
208	.SH EXAMPLES
209	To produce a picture showing the difference between pic1 and pic2:
210	.IP "" .2i
211	pcomb \-e 'ro=ri(1)\-ri(2);go=gi(1)\-gi(2);bo=bi(1)\-bi(2)' pic1 pic2 > diff
212	.PP
213	Or, more efficiently:
214	.IP "" .2i
215	pcomb pic1 \-s \-1 pic2 > diff
216	.PP
217	To precompute the gamma correction for a picture:
218	.IP "" .2i
219	pcomb \-e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' inp.hdr > gam.hdr
220	.PP
221	To perform some special filtering:
222	.IP "" .2i
223	pcomb \-f myfilt.cal \-x xmax/2 \-y ymax/2 input.hdr > filtered.hdr
224	.PP
225	To make a picture of a dot:
226	.IP "" .2i
227	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
228	.SH ENVIRONMENT
229	RAYPATH the directories to check for auxiliary files.
230	.SH AUTHOR
231	Greg Ward
232	.SH "SEE ALSO"
233	getinfo(1), icalc(1), pcompos(1), pfilt(1), rcalc(1),
234	rmtxcomb(1), rmtxop(1), rpict(1)