man/man1/pcomb.1

.\" RCSid "$Id"
.TH PCOMB 1 8/31/96 RADIANCE
.SH NAME
pcomb - combine RADIANCE pictures.
.SH SYNOPSIS
.B pcomb
[
.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.
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 (+/- 8 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.
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.
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.
.PP
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' pic > pic.gam
.PP
To perform some special filtering:
.IP "" .2i
pcomb -f myfilt.cal -x xmax/2 -y ymax/2 input.pic > filtered.pic
.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 AUTHOR
Greg Ward
.SH "SEE ALSO"
calc(1), getinfo(1), pcompos(1), pfilt(1), rpict(1)
Revision:	1.1
Committed:	Tue Mar 11 19:20:21 2003 UTC (21 years, 2 months ago) by greg
Branch:	MAIN
CVS Tags:	rad3R5
Log Message:	Added documentation to repository
#	Content
1	.\" RCSid "$Id"
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 -w
9	][
10	.B "\-x xres"
11	][
12	.B "\-y yres"
13	][
14	.B "\-f file"
15	][
16	.B "\-e expr"
17	]
18	[
19	[
20	.B -o
21	][
22	.B "\-s factor"
23	][
24	.B "\-c r g b"
25	]
26	.B "input .."
27	]
28	.SH DESCRIPTION
29	.I Pcomb
30	combines equal-sized RADIANCE pictures and sends the result to the
31	standard output.
32	By default, the result is just a linear combination of
33	the input pictures multiplied by
34	.I \-s
35	and
36	.I \-c
37	coefficients,
38	but an arbitrary mapping can be assigned with the
39	.I \-e
40	and
41	.I \-f
42	options.
43	Negative coefficients and functions are allowed, and
44	.I pcomb
45	will produce color values of zero where they would be negative.
46	.PP
47	The variables
48	.I ro,
49	.I go
50	and
51	.I bo
52	specify the red, green and blue output values, respectively.
53	Alternatively, the single variable
54	.I lo
55	can be used to specify a brightness value for black and white output.
56	The predefined functions
57	.I ri(n),
58	.I gi(n)
59	and
60	.I bi(n)
61	give the red, green and blue input values for
62	picture
63	.I n.
64	To access a pixel that is nearby the current one, these functions
65	also accept optional x and y offsets.
66	For example,
67	.I ri(3,-2,1)
68	would return the red component of the pixel from picture 3
69	that is left 2 and up 1 from the current position.
70	Although x offsets may be as large as width of the picture,
71	y offsets are limited to a small window (+/- 8 pixels) due to efficiency
72	considerations.
73	However, it is not usually necessary to worry about this problem --
74	if the requested offset is not available, the next best pixel is
75	returned instead.
76	.PP
77	For additional convenience, the function
78	.I li(n)
79	is defined as the input brightness for picture
80	.I n.
81	This function also accepts x and y offsets.
82	.PP
83	The constant
84	.I nfiles
85	gives the number of input files present,
86	and
87	.I WE
88	gives the white efficacy (lumens/brightness) for pixel values.
89	The variables
90	.I x
91	and
92	.I y
93	give the current output pixel location for use in
94	spatially dependent functions, the constants
95	.I xmax
96	and
97	.I ymax
98	give the input resolution, and the constants
99	.I xres
100	and
101	.I yres
102	give the output resolution (usually the same, but see below).
103	The constant functions
104	.I "re(n), ge(n), be(n),"
105	and
106	.I le(n)
107	give the exposure values for picture
108	.I n,
109	and
110	.I pa(n)
111	gives the corresponding pixel aspect ratio.
112	Finally, for pictures with stored view parameters,
113	the functions
114	.I "Ox(n), Oy(n)"
115	and
116	.I Oz(n)
117	return the ray origin in world coordinates for the current pixel
118	in picture
119	.I n,
120	and
121	.I "Dx(n), Dy(n)"
122	and
123	.I Dz(n)
124	return the normalized ray direction.
125	In addition, the function
126	.I T(n)
127	returns the distance from the origin to the aft clipping plane
128	(or zero if there is no aft plane), and the function
129	.I S(n)
130	returns the solid angle of the current pixel in steradians
131	(always zero for parallel views).
132	If the current pixel is outside the view region,
133	.I T(n)
134	will return a negative value, and
135	.I S(n)
136	will return zero.
137	.PP
138	The
139	.I \-w
140	option can be used to suppress warning messages about invalid
141	calculations.
142	The
143	.I \-o
144	option indicates that original pixel values are to be used for the next
145	picture, undoing any previous exposure changes or color correction.
146	.PP
147	The
148	.I \-x
149	and
150	.I \-y
151	options can be used to specify the desired output resolution,
152	.I xres
153	and
154	.I yres,
155	and can be expressions involving other constants such as
156	.I xmax
157	and
158	.I ymax.
159	The constants
160	.I xres
161	and
162	.I yres
163	may also be specified in a file or expression.
164	The default output resolution is the same as the input resolution.
165	.PP
166	The
167	.I \-x
168	and
169	.I \-y
170	options must be present if there are no input files, when
171	the definitions of
172	.I ro,
173	.I go
174	and
175	.I bo
176	will be used to compute each output pixel.
177	This is useful for producing simple test pictures for various
178	purposes.
179	(Theoretically, one could write a complete renderer using just the
180	functional language...)
181	.PP
182	The standard input can be specified with a hyphen ('-').
183	A command that produces a RADIANCE picture can be given in place of a file
184	by preceeding it with an exclamation point ('!').
185	.SH EXAMPLES
186	To produce a picture showing the difference between pic1 and pic2:
187	.IP "" .2i
188	pcomb -e 'ro=ri(1)-ri(2);go=gi(1)-gi(2);bo=bi(1)-bi(2)' pic1 pic2 > diff
189	.PP
190	Or, more efficiently:
191	.IP "" .2i
192	pcomb pic1 -s -1 pic2 > diff
193	.PP
194	To precompute the gamma correction for a picture:
195	.IP "" .2i
196	pcomb -e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' pic > pic.gam
197	.PP
198	To perform some special filtering:
199	.IP "" .2i
200	pcomb -f myfilt.cal -x xmax/2 -y ymax/2 input.pic > filtered.pic
201	.PP
202	To make a picture of a dot:
203	.IP "" .2i
204	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
205	.SH AUTHOR
206	Greg Ward
207	.SH "SEE ALSO"
208	calc(1), getinfo(1), pcompos(1), pfilt(1), rpict(1)