man/man1/pinterp.1

.\" RCSid "$Id: pinterp.1,v 1.6 2008/11/10 19:08:17 greg Exp $"
.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 rvu(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
.I pmdblur(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.hdr 30.z 20.hdr 20.z > 27.hdr
.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.hdr left.z > right.hdr
.PP
To convert an angular fisheye to a hemispherical fisheye:
.IP "" .2i
pinterp \-vf fish.hdr \-vth -ff fish.hdr 1 > hemi.hdr
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
getinfo(1), pdfblur(1), pfilt(1), pmblur(1), pmdblur(1), rpict(1),
ranimate(1), rtrace(1), rvu(1)
Revision:	1.7
Committed:	Sat Feb 21 00:06:05 2009 UTC (16 years, 8 months ago) by greg
Branch:	MAIN
CVS Tags:	rad5R2, rad5R0, rad5R1, rad4R2, rad4R1, rad4R0, rad4R2P1, rad4R2P2
Changes since 1.6:	+5 -1 lines
Log Message:	Added example for converting view type
#	User	Rev	Content
1	greg	1.7	.\" RCSid "$Id: pinterp.1,v 1.6 2008/11/10 19:08:17 greg Exp $"
2	greg	1.1	.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	greg	1.3	.I rvu(1),
35	greg	1.1	.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	greg	1.4	(See
187			.I pmdblur(1).)\0
188	greg	1.1	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	greg	1.6	pinterp \-vf 27.vf \-a \-x 512 \-y 400 \-e +2.5 30.hdr 30.z 20.hdr 20.z > 27.hdr
231	greg	1.1	.PP
232			To extrapolate a second eyepoint for a stereo pair and recalculate
233			background regions:
234			.IP "" .2i
235	greg	1.6	pinterp \-vf right.vf \-ff \-fr "\-av .1 .1 .1 scene.oct" left.hdr left.z > right.hdr
236	greg	1.7	.PP
237			To convert an angular fisheye to a hemispherical fisheye:
238			.IP "" .2i
239			pinterp \-vf fish.hdr \-vth -ff fish.hdr 1 > hemi.hdr
240	greg	1.1	.SH AUTHOR
241			Greg Ward
242			.SH "SEE ALSO"
243	greg	1.4	getinfo(1), pdfblur(1), pfilt(1), pmblur(1), pmdblur(1), rpict(1),
244			ranimate(1), rtrace(1), rvu(1)