man/man1/pinterp.1

.\" RCSid "$Id"
.TH PINTERP 1 1/24/96 RADIANCE
.SH NAME
pinterp - interpolate/extrapolate view from pictures
.SH SYNOPSIS
.B pinterp
[
view options
][
.B "\-t threshold"
][
.B "\-z zout"
][
.B \-f
.I type
][
.B \-B
][
.B \-a|q
][
.B "\-e exposure"
][
.B \-n
]
.B "pictfile zspec .."
.SH DESCRIPTION
.I Pinterp
interpolates or extrapolates a new view from
one or more RADIANCE pictures and
sends the result to the standard output.
The input picture files must contain correct view specifications, as
maintained by
.I rpict(1),
.I rview(1),
.I pfilt(1)
and
.I pinterp.
Specifically,
.I pinterp
will not work on pictures processed by
.I pcompos(1)
or
.I pcomb(1).
Each input file must be accompanied by a z specification, which
gives the distance to each pixel in the image.
If
.I zspec
is an existing file, it is assumed to contain a short floating point
number for each pixel, written in scanline order.
This file is usually generated by the
.I \-z
option of
.I rpict(1).
If
.I zspec
is a positive number rather than a file, it will be used as a
constant value for the corresponding image.
This may be useful for certain transformations on "flat" images or
when the viewpoint remains constant.
.PP
The
.I \-n
option specifies that input and output
z distances are along the view direction,
rather than absolute distances to intersection points.
This option is usually appropriate with a constant z
specification, and should not be used with
.I rpict(1)
z files.
.PP
The
.I \-z
option writes out interpolated z values to the specified file.
Normally, this information is thrown away.
.PP
.I Pinterp
rearranges the pixels from the input pictures to produce a
reasonable estimate of the desired view.
Pixels that map within the
.I \-t
threshold of each other (.02 times the z distance
by default) are considered coincident.
With the
.I \-a
option, image points that coincide will be averaged together, giving
a smooth result.
The
.I \-q
option turns averaging off, which means that the first mapped pixel
for a given point will be used.
This makes the program run faster and
take less memory, but at the expense of image quality.
By default, two or more pictures are averaged together, and a single
picture is treated with the faster algorithm.
This may be undesirable when a quick result is desired from multiple
input pictures in the first case, or a single picture is being
reduced in size (anti-aliased) in the second case.
.PP
Portions which were hidden or missing in the input pictures must be
"filled in" somehow, and a number of methods are provided by the
.I \-f
option.
The default value for this option is
.I \-fa,
which results in both foreground and background filling.
The foreground fill algorithm spreads each input pixel to cover all
output pixels within a parallelogram corresponding to that pixel's
projection in the new view.
Without it, each input pixel contributes to at most one output
pixel.
The background algorithm fills in those areas in the final picture
that have not been filled with foreground pixels.
It does this by looking at the boundary surrounding each blank area
and picking the
farthest pixels to each side, assuming that this will make a suitable
background.
The
.I \-ff
option tells the program to use only the foreground fill, the
.I \-fb
option says use only background fill, and the
.I \-f0
option says not to use either fill algorithm.
.PP
Even when both fill algorithms are used, there may still be some unfilled
pixels.
By default, these pixels are painted black and assigned a z distance
of zero.
The
.I \-fc
option can be used to change the color used for unfilled pixels, and
the
.I \-fz
option can be used to set the z distance (always along the view direction).
Alternatively, the
.I \-fr
option can be used to compute these pixels using
.I rtrace(1).
The argument to this option is a quoted string containing arguments
for
.I rtrace.
It must contain the octree used to generate the input
pictures, along with any other options necessary to match the
calculation used for the input pictures.
The
.I \-fs
option can be used to place a limit on the distance (in pixels) over which
the background fill algorithm is used.
The default value for this option is 0, which is interpreted as no limit.
A value of 1 is equivalent to turning background fill off.
When combined with the
.I \-fr
option, this is roughly equivalent to the 
.I \-ps
option of
.I rpict(1).
.PP
In order of increasing quality and cost, one can use the
.I \-fa
option alone, or the
.I \-fr
option paired with
.I \-fs
or
.I \-ff
or
.I \-f0.
The last combination will result in the recalculation of all pixels
not adequately accounted for in the input pictures, with an
associated computational expense.
It is rare that the
.I \-fs
option results in appreciable image degradation, so it is usually
the second combination that is used when the background fill
algorithm results in objectionable artifacts.
.PP
The
.I \-B
option may be used to average multiple views read from the standard
input into a single, blurred output picture.
This is similar to running
.I pinterp
multiple times and averaging the output together with a program like
.I pcomb(1).
This option is useful for simulating motion blur and depth of field.
(See also
.I pdfblur(1).)\0
The input views are reported in the information header of the output
file, along with the averaged view.
The picture dimensions computed from the first view will be the
ones used, regardless whether or not the subsequent views agree.
(The reported pixel aspect ratio in the output is determined from
these original dimensions and the averaged view.)\0
Note that the expense of the
.I \-fr
option is proportional to the number of views computed, and the
.I \-z
output file will be the z-buffer of the last view interpolated
rather than an averaged distance map.
.PP
In general,
.I pinterp
performs well when the output view is flanked by two nearby input
views, such as might occur in a walk-through animation sequence.
The algorithms start to break down when there is a large difference
between the view desired and the view(s) provided.
Specifically, obscured objects may appear to have holes in them and
large areas at the image borders may not be filled by the
foreground or background algorithms.
Also, specular reflections and highlights will not be interpolated
very well, since their view-dependent appearance will be
incompletely compensated for by the program.
(The
.I \-a
option offers some benefit in this area.)\0
.PP
The
.I \-e
option may be used to adjust the output image exposure, with the
same specification given as for
.I pfilt.
The actual adjustment will be rounded to the nearest integer f-stop
if the
.I \-q
option is in effect (or there is only a single input picture).
.SH EXAMPLE
To interpolate two frames of a walk-through animation, anti-alias to
512x400 and increase the exposure by 2.5 f-stops:
.IP "" .2i
pinterp -vf 27.vf -a -x 512 -y 400 -e +2.5 30.pic 30.z 20.pic 20.z > 27.pic
.PP
To extrapolate a second eyepoint for a stereo pair and recalculate
background regions:
.IP "" .2i
pinterp -vf right.vf -ff -fr "-av .1 .1 .1 scene.oct" left.pic left.z > right.pic
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
getinfo(1), pdfblur(1), pfilt(1), pmblur(1), rpict(1), ranimate(1),
rtrace(1), rview(1)
Revision:	1.1
Committed:	Tue Mar 11 19:20:21 2003 UTC (22 years, 7 months ago) by greg
Branch:	MAIN
CVS Tags:	rad3R5
Log Message:	Added documentation to repository
#	Content
1	.\" RCSid "$Id"
2	.TH PINTERP 1 1/24/96 RADIANCE
3	.SH NAME
4	pinterp - interpolate/extrapolate view from pictures
5	.SH SYNOPSIS
6	.B pinterp
7	[
8	view options
9	][
10	.B "\-t threshold"
11	][
12	.B "\-z zout"
13	][
14	.B \-f
15	.I type
16	][
17	.B \-B
18	][
19	.B \-a\|q
20	][
21	.B "\-e exposure"
22	][
23	.B \-n
24	]
25	.B "pictfile zspec .."
26	.SH DESCRIPTION
27	.I Pinterp
28	interpolates or extrapolates a new view from
29	one or more RADIANCE pictures and
30	sends the result to the standard output.
31	The input picture files must contain correct view specifications, as
32	maintained by
33	.I rpict(1),
34	.I rview(1),
35	.I pfilt(1)
36	and
37	.I pinterp.
38	Specifically,
39	.I pinterp
40	will not work on pictures processed by
41	.I pcompos(1)
42	or
43	.I pcomb(1).
44	Each input file must be accompanied by a z specification, which
45	gives the distance to each pixel in the image.
46	If
47	.I zspec
48	is an existing file, it is assumed to contain a short floating point
49	number for each pixel, written in scanline order.
50	This file is usually generated by the
51	.I \-z
52	option of
53	.I rpict(1).
54	If
55	.I zspec
56	is a positive number rather than a file, it will be used as a
57	constant value for the corresponding image.
58	This may be useful for certain transformations on "flat" images or
59	when the viewpoint remains constant.
60	.PP
61	The
62	.I \-n
63	option specifies that input and output
64	z distances are along the view direction,
65	rather than absolute distances to intersection points.
66	This option is usually appropriate with a constant z
67	specification, and should not be used with
68	.I rpict(1)
69	z files.
70	.PP
71	The
72	.I \-z
73	option writes out interpolated z values to the specified file.
74	Normally, this information is thrown away.
75	.PP
76	.I Pinterp
77	rearranges the pixels from the input pictures to produce a
78	reasonable estimate of the desired view.
79	Pixels that map within the
80	.I \-t
81	threshold of each other (.02 times the z distance
82	by default) are considered coincident.
83	With the
84	.I \-a
85	option, image points that coincide will be averaged together, giving
86	a smooth result.
87	The
88	.I \-q
89	option turns averaging off, which means that the first mapped pixel
90	for a given point will be used.
91	This makes the program run faster and
92	take less memory, but at the expense of image quality.
93	By default, two or more pictures are averaged together, and a single
94	picture is treated with the faster algorithm.
95	This may be undesirable when a quick result is desired from multiple
96	input pictures in the first case, or a single picture is being
97	reduced in size (anti-aliased) in the second case.
98	.PP
99	Portions which were hidden or missing in the input pictures must be
100	"filled in" somehow, and a number of methods are provided by the
101	.I \-f
102	option.
103	The default value for this option is
104	.I \-fa,
105	which results in both foreground and background filling.
106	The foreground fill algorithm spreads each input pixel to cover all
107	output pixels within a parallelogram corresponding to that pixel's
108	projection in the new view.
109	Without it, each input pixel contributes to at most one output
110	pixel.
111	The background algorithm fills in those areas in the final picture
112	that have not been filled with foreground pixels.
113	It does this by looking at the boundary surrounding each blank area
114	and picking the
115	farthest pixels to each side, assuming that this will make a suitable
116	background.
117	The
118	.I \-ff
119	option tells the program to use only the foreground fill, the
120	.I \-fb
121	option says use only background fill, and the
122	.I \-f0
123	option says not to use either fill algorithm.
124	.PP
125	Even when both fill algorithms are used, there may still be some unfilled
126	pixels.
127	By default, these pixels are painted black and assigned a z distance
128	of zero.
129	The
130	.I \-fc
131	option can be used to change the color used for unfilled pixels, and
132	the
133	.I \-fz
134	option can be used to set the z distance (always along the view direction).
135	Alternatively, the
136	.I \-fr
137	option can be used to compute these pixels using
138	.I rtrace(1).
139	The argument to this option is a quoted string containing arguments
140	for
141	.I rtrace.
142	It must contain the octree used to generate the input
143	pictures, along with any other options necessary to match the
144	calculation used for the input pictures.
145	The
146	.I \-fs
147	option can be used to place a limit on the distance (in pixels) over which
148	the background fill algorithm is used.
149	The default value for this option is 0, which is interpreted as no limit.
150	A value of 1 is equivalent to turning background fill off.
151	When combined with the
152	.I \-fr
153	option, this is roughly equivalent to the
154	.I \-ps
155	option of
156	.I rpict(1).
157	.PP
158	In order of increasing quality and cost, one can use the
159	.I \-fa
160	option alone, or the
161	.I \-fr
162	option paired with
163	.I \-fs
164	or
165	.I \-ff
166	or
167	.I \-f0.
168	The last combination will result in the recalculation of all pixels
169	not adequately accounted for in the input pictures, with an
170	associated computational expense.
171	It is rare that the
172	.I \-fs
173	option results in appreciable image degradation, so it is usually
174	the second combination that is used when the background fill
175	algorithm results in objectionable artifacts.
176	.PP
177	The
178	.I \-B
179	option may be used to average multiple views read from the standard
180	input into a single, blurred output picture.
181	This is similar to running
182	.I pinterp
183	multiple times and averaging the output together with a program like
184	.I pcomb(1).
185	This option is useful for simulating motion blur and depth of field.
186	(See also
187	.I pdfblur(1).)\0
188	The input views are reported in the information header of the output
189	file, along with the averaged view.
190	The picture dimensions computed from the first view will be the
191	ones used, regardless whether or not the subsequent views agree.
192	(The reported pixel aspect ratio in the output is determined from
193	these original dimensions and the averaged view.)\0
194	Note that the expense of the
195	.I \-fr
196	option is proportional to the number of views computed, and the
197	.I \-z
198	output file will be the z-buffer of the last view interpolated
199	rather than an averaged distance map.
200	.PP
201	In general,
202	.I pinterp
203	performs well when the output view is flanked by two nearby input
204	views, such as might occur in a walk-through animation sequence.
205	The algorithms start to break down when there is a large difference
206	between the view desired and the view(s) provided.
207	Specifically, obscured objects may appear to have holes in them and
208	large areas at the image borders may not be filled by the
209	foreground or background algorithms.
210	Also, specular reflections and highlights will not be interpolated
211	very well, since their view-dependent appearance will be
212	incompletely compensated for by the program.
213	(The
214	.I \-a
215	option offers some benefit in this area.)\0
216	.PP
217	The
218	.I \-e
219	option may be used to adjust the output image exposure, with the
220	same specification given as for
221	.I pfilt.
222	The actual adjustment will be rounded to the nearest integer f-stop
223	if the
224	.I \-q
225	option is in effect (or there is only a single input picture).
226	.SH EXAMPLE
227	To interpolate two frames of a walk-through animation, anti-alias to
228	512x400 and increase the exposure by 2.5 f-stops:
229	.IP "" .2i
230	pinterp -vf 27.vf -a -x 512 -y 400 -e +2.5 30.pic 30.z 20.pic 20.z > 27.pic
231	.PP
232	To extrapolate a second eyepoint for a stereo pair and recalculate
233	background regions:
234	.IP "" .2i
235	pinterp -vf right.vf -ff -fr "-av .1 .1 .1 scene.oct" left.pic left.z > right.pic
236	.SH AUTHOR
237	Greg Ward
238	.SH "SEE ALSO"
239	getinfo(1), pdfblur(1), pfilt(1), pmblur(1), rpict(1), ranimate(1),
240	rtrace(1), rview(1)