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1.1 root 1: .so ../ADM/mac
2: .XX raster 483 "The 10th Edition Raster Graphics System"
3: .fp 5 T CW \" T for Typewriter
4: .de TP \" An indented paragraph describing some command, tagged with the command name
5: .IP "\\fT\\$1\\fR" 8
6: .if \\w'\\fT\\$1\\fR'-7n .br
7: ..
8: .de CI
9: .nr Sf \\n(.f
10: \%\&\\$3\f(CW\\$1\fI\&\\$2\f\\n(Sf
11: ..
12: .TL
13: The 10th Edition Raster Graphics System
14: .AU
15: Tom Duff
16: .AI
17: .MH
18: .AB
19: The current (late 1989) state of generating and displaying raster graphics
20: in Research
21: .UX
22: is described.
23: .AE
24: .2C
25: .NH
26: Introduction
27: .PP
28: The Research
29: .UX
30: system contains a number of commands to capture, manipulate,
31: display and record monochrome and full-color raster images. Three groups of
32: commands may be identified:
33: interactive programs that operate on a frame buffer,
34: commands that operate on images stored in picture
35: files (see
36: .I picfile (5)),
37: and programs that interface to various graphical I/O devices:
38: video cameras, scanners, paper plotters, film cameras and video tape
39: recorders.
40: .NH
41: Video Facilities
42: .PP
43: No discussion of our raster graphics software can ignore the
44: hardware on which it runs. The hardware available at different
45: sites will, of course, vary. For definiteness, and to provide
46: help for the local audience, this section will discuss the
47: hardware available in Center 1127's graphics and image processing
48: laboratory (MH 2C-524) and its neighborhood. Most other environments
49: will have hardware that is similar in spirit if different in detail.
50: .PP
51: There are seven work stations in 2C-528. On the day this was written,
52: four of them had TTY 5620 terminals, two had Gnot terminals and
53: one had a SUN-3 workstation computer. Eventually, most of the 5620's
54: will be replaced with Gnots. Each work station also has
55: a Sony GDM-1901-12 video monitor that displays high-resolution
56: video signals.
57: .PP
58: The room contains other video displays and recorders, including
59: a Barco video projector in the ceiling, a 35-inch Mitsubishi monitor
60: at the front of the room, a 19-inch Barco monitor at work station 6,
61: two small Sony monitors in the video rack next to the audio console,
62: two Panasonic Super-VHS recorders, a Sony 3/4-inch (U-MATIC) video
63: player, a multi-standard (SECAM, NTSC, PAL) VHS player, a
64: Sony BVH-2500 1-inch (SMPTE-C) video tape recorder and a Sony video
65: camera.
66: .PP
67: The video equipment supports at least three incompatible video formats.
68: High-resolution
69: RGB video has 1024 scan lines, a 60 hz non-interlaced vertical scan rate,
70: and transmits red, green and blue information on separate cables with
71: synchronization pulses superimposed on the green channel.
72: Low-resolution RGB video has between 480 and 488 scan lines, 30hz
73: interlaced vertical scan, and separate RGB with sync on green.
74: NTSC (National Television Standards Committee) video has the same timing
75: characteristics as low-resolution RGB video, but encodes red, green, blue
76: and sync into a single signal.
77: NTSC is the encoding used by American, Canadian and Japanese television
78: broadcasters, and by almost all video recording and playback equipment
79: in those countries.
80: .PP
81: Various computer terminals generate video in other formats that our
82: equipment handles with only limited success. Gnots, 630s,
83: 5620s, Sun terminals, IBM-compatible PCs and Macintoshes all generate
84: mutually incompatible video. Their vertical and horizontal scan-rates
85: differ. The voltages and impedances of the signals they produce differ.
86: Their color encodings differ. Monitors that can display video from all
87: of these sources are rare, let alone hardware to convert from one format
88: to another. For example, the only reliable way to record a signal from
89: any of these sources is to place a camera in front of a monitor. The
90: quality of the resulting recordings is often bad. It is a black art
91: to adjust our Barco video projector to handle non-standard signals,
92: but with a few days notice it can often be done. Again, the results
93: are not often as good as one might like \(mi the projector does not
94: focus as tightly as a monitor and its brightness is limited. As better
95: video displays become available our situation will improve.
96: Table 1 summarizes the equipment available and the
97: video formats that each supports.
98: .1C
99: .KF
100: .TS
101: center box;
102: l| c| c| c| c| c| c.
103: Equipment High-res Low-res NTSC Gnot IBM PAL/SECAM
104: RGB RGB
105: =
106: workstation monitors \(bu
107: _
108: Barco projector \(bu \(bu \(bu \(bu maybe maybe
109: _
110: 35-inch Mitsubishi \(bu \(bu \(bu
111: _
112: Barco at work station 6 \(bu \(bu
113: _
114: Sony rack monitors \(bu
115: _
116: Super-VHS recorders \(bu
117: _
118: U-MATIC player \(bu
119: _
120: 1-inch recorder \(bu
121: _
122: multi-standard player \(bu \(bu
123: _
124: camera \(bu \(bu
125: _
126: Metheus frame buffers \(bu
127: _
128: ITI frame buffer \(bu
129: _
130: Pixel Machine \(bu \(bu
131: .TE
132: .sp .3
133: .ce
134: \fBTable 1. \fRVideo devices
135: .SP .5
136: .KE
137: .2C
138: .PP
139: We have several Metheus 3610 frame buffers (seven on
140: .CW pipe ,
141: one on
142: .CW arend ,
143: one on
144: .CW encke )
145: and an Imaging Technology, Inc. (ITI) RGB-512. All of our
146: frame buffers store 32 bits at each pixel, one byte each for red, green
147: blue and alpha. The 3610's generate high-resolution (1280\(mu1024)
148: video. The ITI generates low-resolution (512\(mu480) video that may
149: be recorded on video tape after conversion to NTSC. Connected to
150: .CW pyxis ,
151: a four CPU SGI 4D-240, is an AT&T Pixel Machine with
152: 58 processors. It can generate either high- or low-resolution video
153: under software control; the Pixel Machine documentation can tell you how.
154: .PP
155: Each piece of video equipment may be connected to any other
156: via a video patch bay in 2C-538 (the
157: .CW alice
158: room.) Alternating
159: rows of the patch bay present video outputs and inputs. If
160: an output and the input immediately below it are not plugged
161: into anything, an internal connection routes one to the other.
162: The patch bay has been layed out so that the most useful
163: configurations require no patch cords. The patch bay is carefully
164: labelled so that its proper use ought to be obvious.
165: .PP
166: The Sony BVH-2500 video recorder produces very high
167: quality recordings on 1" video tape. Since it can overwrite
168: arbitrary single frames of the tape, it is an ideal machine
169: on which to record animation.
170: .PP
171: Before using a new tape,
172: you must record (``grind'') time-code on it, numbering
173: each frame of the tape.
174: Time-code values are usually denoted by values
175: of the form
176: .I hh.mm.ss.ff
177: (like
178: .CW 02.43.17.15 ).
179: The 2500's monitor output, available on the video patch bay,
180: displays time-code superimposed on the 2500's
181: output signal.
182: .PP
183: To grind time-code, use
184: the patch bay
185: to connect the color bar generator
186: to the 2500's input, thread up a tape, and manually set the
187: 2500 to record by pushing its
188: .CW REC
189: and
190: .CW PLAY
191: buttons simultaneously. Let it go until the tape runs out.
192: .PP
193: The
194: .I 2500
195: command operates the recorder, reading instructions
196: from its standard input. Its instruction set is
197: moderately complicated; for most uses the following
198: subset is adequate:
199: .TP "cue \fIhh.mm.ss.ff
200: Cue the tape to the given time code. The
201: time-code displayed on the 2500's monitor
202: output may be a few frames off,
203: but the recorder will be cued to the correct point.
204: .TP "still mode on
205: Put the recorder in single-frame record mode.
206: .TP "still mode off\fP
207: Put the recorder out of single-frame record mode.
208: .TP "snap [\fIn\fT]
209: Record
210: .I n
211: frames (default 1) at the current cue point, and
212: advance the cue point by
213: .I n
214: frames. The recorder must be in single frame mode.
215: .TP "play
216: Start playing back from the current cue point.
217: .TP "stop
218: Stop the recorder.
219: .TP "!\fIunix-command
220: Run the given
221: .I unix-command
222: using
223: .CW /bin/sh .
224: .PP
225: We currently have only two sources of digital video that
226: may be recorded on video tape. These are the Pixel Machine
227: and the ITI frame buffer attached to
228: .CW kwee .
229: To use either
230: one, you must patch its output to the NTSC color encoder,
231: and patch the encoder's output to the video recorder.
232: The ITI frame buffer is also useful as a frame-grabber,
233: capturing its video input in its memory whence it may
234: be saved in a picture file or otherwise manipulated.
235: .PP
236: The ITI is served by an ancient software regime whose
237: commands all begin with the letters
238: .CW iti .
239: .TP "itifbinit [-x]
240: Re-initialize the ITI to the state expected by the
241: rest of the software. The ITI is often unused for
242: days at at time, during which its health often
243: decays.
244: .CW itifbinit
245: is its restorative. The
246: .CW -x
247: flag causes its output signal to be synchronized to the
248: sync pulses of its input, instead of running from its
249: internal clock.
250: This is always a good idea.
251: .TP itigamma
252: Load the ITI's color map to correct intensities
253: for display on CRT monitors.
254: .TP "itigrab [-gs]
255: Run the frame-grabber. The
256: .CW -g
257: flag starts the frame-grabber running.
258: The displayed image will track the ITI's input
259: video.
260: .CW -s
261: stops the frame-grabber, freezing the image.
262: Unadorned by flags,
263: .CW grab
264: starts the frame-grabber and stops it one frame
265: later.
266: .TP "itigit \fIpicture-file
267: Copy the image stored in
268: .I picture-file
269: into the ITI.
270: .TP "itisiv \fIpicture-file
271: Save the image in the ITI in
272: .I picture-file .
273: .NH
274: Other output devices
275: .PP
276: Many modern laser printers and typesetters read data in the PostScript format.
277: .TP "pic2ps [-h \fIheight\fP] [\fIpicture\fP]
278: converts a picture file into encapsulated PostScript, suitable for inclusion
279: in any PostScript document. The
280: .CW -h
281: option specifies the height, in inches, of the output image. It is
282: not often required, as document processors usually insert PostScript illustrations
283: in a scale-independent manner.
284: .PP
285: The
286: .CW alice
287: room contains an Imagitex scanner that can be used to
288: convert photographs to digital form. To use it, place the image to be scanned
289: under the hold-down leaves, slide the leaves to make a window around the section
290: you wish to scan, and use the
291: .I imscan
292: command.
293: .TP "imscan [-s\fIscale\fP] [-l\fIlens\fP] file" .
294: The
295: .CW -l
296: option causes the scanner to use a lens of
297: focal length
298: .I lens
299: inches.
300: The possibilities are 5 (754 dots per inch) and 8 (480 dots per inch); 8 is the default.
301: The
302: .CW -s
303: option sets the sub-sampling
304: .I scale ,
305: which can vary from 1 to 9. One pixel in each
306: .I scale
307: by
308: .I scale
309: square will be stored. The default is 4. In conjunction with
310: the default 8-inch lens, this causes scans to be stored at 120 dot-per-inch resolution.
311: .PP
312: There is a high-resolution one-bit-per-pixel Canon document scanner at the back of the graphics lab accessed through the
313: .I cscan
314: command.
315: .TP "cscan [-f\fIx\fP,\fIy\fP] [-fL] [-s\fIseconds\fP] [-v] [\fIfile ...\fP]
316: scans pages into the given files (default, one page onto standard output.)
317: The
318: .CW -f
319: option sets the size of the scan in pixels (400 to the inch);
320: .CW -fL
321: sets double-letter size (11 by 17 inches, the largest possible.)
322: The
323: .CW -s
324: option sets the number of seconds to wait before scanning each page after
325: the first.
326: .PP
327: In the Alice room is a Matrix Instruments QCR digital film recorder.
328: It will record color or black-and-white images in a variety of photographic
329: formats, include 8x10 Polaroid, 4x5 and 35mm. The
330: .I qsnap (1)
331: command will output an image to film.
332: \ \ \ \ \ \ \
333: .NH
334: Frame buffer commands
335: .PP
336: A frame buffer is a large memory organized as a two-dimensional array of
337: pixels. Our Metheus 3610 frame buffers have 1024 scan lines of 1280 pixels
338: each. The ITI frame buffer has 480 lines of 512 pixels. The coordinate
339: system has (0,0) in the upper left-hand corner, with x increasing to
340: the right, and y increasing down. This apparent weirdness is fairly standard,
341: since it makes video output happen in row-major order.
342: .PP
343: Here we will mostly discuss commands for the Metheus displays. The corresponding
344: ITI commands have the same names, but prefixed with the string
345: .CW iti .
346: .PP
347: There are seven Metheus frame buffers attached to pipe, named
348: .CW /dev/om[0-6] .
349: All of the commands discussed below determine which one to use
350: by examining the environment variable
351: .CW FB .
352: It is often hard to tell what frame buffer is displayed on which monitor
353: because of connections in the patch bay. The
354: .CW fbi
355: (frame buffer identification) command displays each frame buffer's name in it.
356: .PP
357: Our frame buffers all have 32 bits per pixel, divided into
358: four 8-bit channels. The channel values are normally thought of
359: as fractions ranging from 0 to 1, although frame buffer commands perversely
360: refer to them as integers between 0 and 255.
361: Three of the channels specify the red, green and
362: blue color components of the image. The fourth channel, called
363: .I alpha ,
364: is used to indicate whether or not the image covers the pixel, and is not
365: normally displayed.
366: .I Alpha
367: is used to control image compositing operations|reference(porter duff compositing digital images).
368: Fractional values of
369: .I alpha
370: describe pixels that the image partly or translucently covers, and
371: facilitate anti-aliased compositing.
372: .PP
373: Each frame buffer contains three 256 entry look-up tables that specify
374: mappings from the values stored in the red, green and blue channels
375: to the voltages supplied at the frame buffers' video outputs.
376: A couple of commands manipulate these mappings.
377: .TP "gamma [\fIpower\fP]
378: command loads these tables with a function that
379: inverts the power-law relation between voltage and luminous flux
380: normally encountered in CRT displays. Thus, pixel values normally
381: correspond directly to displayed intensities.
382: .I Power
383: is the exponent of the power-law. The default of 2.3 is adequate
384: for all our displays.
385: .TP "getmap \fIfile\fP [...]
386: command, whose arguments are a list of files containing color maps.
387: On the ITI, the argument `\fT%\fP' refers
388: to the current content of the frame buffer's color map. (The Metheuses'
389: color maps are write-only.) The functional composition of the specified
390: color maps is loaded into the frame buffer's color map.
391: .I Getmap
392: searches for files in
393: .CW . ,
394: then
395: .CW /fb/cmap ,
396: then
397: .CW /usr/td/2d/cmap/lib .
398: A color map file contains 256 records of 3 bytes each, specifying the output
399: values for the corresponding red, green and blue input values.
400: .TP ranmap
401: command loads random values into the color map.
402: .PP
403: The
404: .I zoom
405: and
406: .I movie
407: commands support magnification and animation of images.
408: .TP "zoom [\fIamount\fP [\fIx y\fP]]
409: magnifies part of the image.
410: With three arguments,
411: .I zoom
412: magnifies by
413: .I amount ,
414: mapping the point
415: .I x,y ) (
416: (default (0,0)) to the upper left-hand corner of the screen.
417: With no arguments,
418: .I amount
419: defaults to 1.
420: The Metheuses can magnify by any integral factor from 1 to 16.
421: The ITI can magnify only by 1 or 2.
422: .TP "movie \fIxsize ysize nx ny\fP [\fIdelay\fP]
423: views an array of images in sequence by zooming and panning.
424: The arguments are the size of the individual
425: frames, the number of frames in the array in each
426: direction, and optionally the number of 60ths of a second
427: to delay between frames. The frames must be arranged
428: boustrophedonically, with alternate rows proceeding from
429: left to right and right to left. (This is because neither
430: Metheus nor ITI frame buffers can pan in x and y simultaneously
431: without glitching.)
432: .PP
433: There are a number of commands to load simple patterns into the frame buffer:
434: .TP "clr [-w \fIx0 y0 x1 y1\fT] [\fIr\fT [\fIg b\fT [\fIalpha\fT]]]
435: sets all pixels to the given value. If only
436: .I r
437: is given,
438: .I g
439: and
440: .I b
441: are set to
442: .I r .
443: If
444: .I alpha
445: is not given, it is set to 255 (completely opaque.)
446: The
447: .CW -w
448: flag restricts attention to pixels inside the window whose upper-left corner is
449: .I x0,y0 ) (
450: and with
451: .I x1,y1 ) (
452: just diagonally outside the lower-right corner.
453: .TP cbars
454: displays a color-bars test pattern. The 8 bars at the top exercise all combinations
455: of the 3 primary colors. The 9 patches at the bottom are a logarithmic
456: (perceptually uniform) grey scale.
457: .TP "ramp [-w \fIx0 y0 x1 y1\fT] [-v] [[\fIc0\fT] \fIc1\fT]
458: displays a horizontal ramp whose color is
459: .I c0
460: at the left
461: and
462: .I c1
463: at the right.
464: Colors are specified as for
465: .CW clr
466: (green and blue default equal to red, alpha defaults to 255).
467: .I C0
468: defaults to
469: .CW "0 0 0 255" .
470: .CW -w
471: restricts
472: .CW ramp
473: to the given window.
474: .CW -v
475: gives a vertical ramp with
476: .I c0
477: at the top
478: and
479: .I c1
480: at the bottom.
481: .TP "colors [-gfr]
482: displays a 16 by 16 array of grey-colored (equal red, green and blue) squares in
483: the middle of the screen with red, green and blue ramps at the top. This is
484: mostly useful for examining color maps. The flags modify the display in small ways.
485: .CW -r
486: suppresses the ramps.
487: .CW -g
488: suppresses the gaps between the squares.
489: .CW -f
490: expands the display to fill the full screen, making the patches non-square and
491: suppressing the ramps.
492: .PP
493: The
494: .I xhair
495: command can be used to examine the contents of the frame buffer.
496: It is named after the cross-hair that it draws on the screen. Single
497: character commands manipulate the cross-hair, magnify the video and
498: print pixel values. The commands are
499: .nf
500: .ta 8n
501: \fTh\fP print the help message
502: \fTlrud\fP move left, right, up or down 1 pixel
503: \fTLRUD\fP move left, right, up or down 16 pixels
504: \fT0\fP move to center of screen (x=256, y=240)
505: \fT1-8\fP magnify \(mu1\-8
506: \fT9\fP magnify \(mu16
507: \fTp\fP print current coordinates and pixel value
508: \fTP\fP print pixel after each command (toggle)
509: \fTm\fP type coordinates to move to
510: \fTx\fP type x coordinate to move to
511: \fTy\fP type y coordinate to move to
512: \fTc\fP change the crosshair display to a rectangle
513: \fTs\fP manipulate other corner of rectangle
514: \fT^D,q\fP exit xhair and run command
515: \fTQ\fP exit xhair, don't demagnify or run command
516: \fTX\fP exit and don't run command
517: .PP
518: If
519: .I xhair
520: is given arguments, they represent a command to be executed before exiting,
521: after making substitutions for any argument whose first character is
522: .CW % .
523: The substitutions made are:
524: .ta 8n
525: .nf
526: \fT%r\fP the current rectangle
527: \fT%w\fP the current rectangle
528: \fT%p\fP the upper-left corner of the rectangle
529: \fT%o\fP the upper-left corner of the rectangle
530: \fT%c\fP the lower-right corner of the rectangle
531: \fT%x\fP the x coordinate of the upper-left corner
532: \fT%y\fP the y coordinate of the upper-left corner
533: \fT%X\fP the x coordinate of the lower-right corner
534: \fT%Y\fP the y coordinate of the lower-right corner
535: .PP
536: The
537: .I mplot
538: command is a version of the standard UNIX
539: .I plot (1)
540: filter that produces output in a Metheus frame buffer.
541: .NH
542: Picture file commands
543: .PP
544: Most of our raster graphics commands require no special hardware. They synthesize
545: images in picture files from textual or other descriptions, they modify images
546: in picture files, producing results in picture files, or they combine the contents
547: of several picture files to produce composite images, again storing the result in
548: a picture file.
549: .PP
550: The
551: .I pcp
552: command takes two names of picture files or frame buffers and copies the first onto the second.
553: As with all picture file commands, the special names
554: .CW IN
555: and
556: .CW OUT
557: refer to standard input and standard output.
558: Frame buffers are designated by names that begin with \fT%\fP:
559: .ta 8n
560: .nf
561: \fT%0\fP Metheus frame buffer #0.
562: \&...
563: \fT%9\fP Metheus frame buffer #9.
564: .fi
565: .PP
566: .I Pcp
567: has a number of options that alter the copied picture:
568: .TP "-o\ \fIx y
569: Add
570: .I x,y ) (
571: to the picture's window coordinates.
572: .TP "-w \fIx0\ y0\ x1\ y1
573: Clip the input picture's window to the given coordinates.
574: If
575: .CW -o
576: and
577: .CW -w
578: are both given, the window is clipped before being offset.
579: .TP "-t\ \fItype
580: The output picture will have
581: .CW "TYPE= \fItype" .
582: .TP "-c\ \fIchannels
583: The output picture will be assembled from the given
584: channels of the input picture. In many cases, a request
585: for a channel not found in the input picture will be
586: satisfied by standard conversions.
587: For example, if
588: .I channels
589: includes
590: .CW m ,
591: but the input picture has only
592: .CW rgb ,
593: a monochrome channel is synthesized by computing
594: NTSC luminance (\fTm=.299r+.587g+.114b\fP).
595: Conversely,
596: .CW rgb
597: will be synthesized from
598: .CW m
599: by lookup in the input's color map, if it has one, or by
600: .CW r=g=b
601: otherwise.
602: If
603: .I channels
604: mentions
605: .CW a
606: and the input has none, 255 is used.
607: If
608: .I channels
609: mentions
610: .CW z...
611: and the input has none, 1.0 (floating point) is used.
612: Any other channel missing in the input is set to zero.
613: .TP "-C\ \fIchannels"
614: Put
615: .CW CHAN=\fIchannels
616: in the output's header. Without this option, the
617: output's
618: .CW CHAN
619: attribute is taken from the
620: .CW -c
621: option, or failing that from the input's
622: .CW CHAN
623: attribute.
624: .CW -C
625: is useful, for example, to create a monochrome (\fTCHAN=m\fP)
626: image from the red channel of a color image using
627: .CW "pcp -cr -Cm" .
628: .PP
629: The
630: .I lam
631: command combines any number of images, writing a picture file whose window
632: is large enough to contain all the windows of its inputs. The input files
633: are combined with pixels of later images overwriting earlier ones.
634: This is only really useful if the windows of the input images differ.
635: .CI -o " file
636: specifies the output file name (standard output by default).
637: All input images must have the same
638: .CW NCHAN .
639: .PP
640: The
641: .I posit
642: and
643: .I 3matte
644: commands combine images using the two- and three-dimensional compositing
645: operations described in |reference(porter duff compositing digital images)
646: and |reference(duff composite3d).
647: Each takes a list of picture file names as arguments, producing a composite
648: on standard output. The
649: .CW -a
650: option will cause either program to output only the
651: .CW rgb
652: channels, suppressing
653: .CW a
654: (and
655: .CW z...
656: in the case of
657: .I 3matte ).
658: .PP
659: There is an army of commands to read an image and, under the control of a few
660: parameters, write a modified image on standard output. Those that read
661: a single picture file by default use standard input, so they are usable
662: in a pipeline.
663: They include:
664: .TP "lum [\fIpicture\fP]
665: File
666: .I picture
667: (default standard input) contains a color image or a monochrome image with a color map.
668: A gray-level image is written on standard output,
669: using the NTSC luminance formula.
670: .TP "clip [-o \fIx y\fP] \fIx0 y0 x1 y1\fP [\fIpicture\fP]
671: Clip an image to have
672: .CW "WINDOW=\fIx0 y0 x1 y1" .
673: A picture that does not fill out the window is filled with black pixels.
674: .TP "xpand [-s] [\fIpicture\fP] [\fIlo hi\fP [\fIinlo inhi\fP]]
675: The input picture has its dynamic range adjusted so that pixels in the
676: range
677: .I inlo
678: to
679: inhi
680: are mapped to the range
681: .I lo
682: to
683: .I hi
684: (default 0 to 255).
685: The default values for
686: .I inlo
687: and
688: .I inhi
689: are determined per channel by examining the input picture.
690: The
691: .CW -s
692: option causes all channels to be examined together.
693: .I Lo ,
694: .I hi ,
695: .I inlo
696: and
697: .I inhi
698: may have any values whatsoever. If
699: .I hi
700: is smaller than
701: .I lo ,
702: pixel values will be inverted, producing a negative image.
703: Any output pixel that would be mapped outside the range
704: 0\-255 is set to 0 or 255.
705: .TP "dither [\fIpicture\fP]
706: Convert a full-color (3 channel) picture to one channel with a color map
707: by dithering.
708: .TP "floyd [\fIpicture\fP]
709: Convert an 8-bit gray-scale picture to one bit per pixel using a version of the Floyd-Steinberg
710: error-diffusion method.
711: .TP "halftone \fIscreen\fP [\fIpicture\fP]
712: Convert an 8-bit gray-scale picture to one bit using a given half-tone
713: .I screen .
714: A description of the screen is read from a file in
715: .CW /usr/td/lib/screens .
716: The available screens include (among others)
717: .KS
718: .in 2n
719: .TS
720: lFCW l.
721: ALLEBACH Allebach's ordered-dither
722: BAYER Standard ordered-dither
723: BLUENOISE A pebble-screen pattern
724: CLASSIC A 3-pixel-wide dot screen
725: CLASSIC2 Another 3-pixel-wide dot screen
726: CLASSIC3 A 4-pixel-wide dot screen
727: CLASSIC4 An 8-pixel-wide dot screen
728: DIAMOND Rao and Arce's ordered-dither
729: LINE Ulichney's line screen
730: RING A concentric ring screen
731: TILT18 A tilted dot screen
732: .TE
733: .KE
734: .TP "he [\fIpicture\fP]
735: Histogram equalization: the intensity histogram
736: of the input image is measured. The output image
737: has its contrast altered for maximum use of the
738: output range, equalizing the histogram
739: as much as possible.
740: .TP "hysteresis \fIlow high\fP [\fIpicture\fP]
741: Pixel values of
742: .I picture
743: below
744: .I low
745: are mapped to zero.
746: Those above
747: .I high
748: are mapped to 255.
749: If
750: .I low
751: and
752: .I high
753: are not equal, any region
754: below
755: .I high
756: that has any 8-connected neighbors below
757: .I low
758: is mapped to zero.
759: .TP "picaverage \fIweight picture1 picture2
760: The output picture is a weighted average of
761: .I picture1
762: and
763: .I picture2 .
764: .I Weight
765: determines the fraction of the average contributed by
766: .I picture1 .
767: .TP "piccat \fIpicture ...
768: The input
769: .I picture s
770: are concatenated one atop another. The
771: output has the width of the widest input.
772: .TP "picjoin \fIpicture ...
773: The input
774: .I picture s
775: are concatenated side by side. The
776: output has the height of the highest input.
777: .TP "adapt [\fIpicture\fP]
778: Adaptive contrast enhancement: a 7 by 7 neighborhood around each pixel
779: is examined for its minimum and maximum values. The center pixel is
780: remapped linearly in a way that would send the neighborhood's maximum to
781: 255 and its minimum to 0. That is,
782: .CW "cen=255*(cen-min)/(max-min)" .
783: .TP "ahe [\fIpicture\fP]
784: Adaptive histogram equalization: each pixel of the output image
785: is the histogram-equalized value of the center of a 17\(mu17 pixel
786: window surrounding it in the input image.
787: .TP "clean [\fIpicture\fP]
788: Bayer-Powell noise removal filter. If the center pixel of each 3\(mu3
789: window in the input differs from the average of the other 8 pixels by
790: more than 64, it is replaced by the periphery-average. This has the
791: effect of flattening isolated noise pixels.
792: .TP "crispen [\fIpicture\fP]
793: 3\(mu3 linear crispening filter. Convolves the input image with
794: the kernel
795: .P1 20n
796: -1 -1 -1
797: -1 9 -1
798: -1 -1 -1
799: .P2
800: This is a mild high-pass filter.
801: .TP "edge [\fIpicture\fP]
802: 3\(mu3 linear edge-detection filter.
803: Convolves the input image with
804: the kernel
805: .P1 20n
806: -1 -1 -1
807: -1 8 -1
808: -1 -1 -1
809: .P2
810: This is just the difference between the original image and the output of
811: .CW crispen .
812: .TP "edge2 [\fIpicture\fP]
813: 3\(mu3 non-linear edge-detection (Sobel operator) filter.
814: .TP "extremum [\fIpicture\fP]
815: 3\(mu3 extremum filter. Replaces the center pixel of each
816: by the value in the 3\(mu3 window surrounding it that most
817: differs from it.
818: .TP "laplace [\fIpicture\fP]
819: 3\(mu3 Laplacian filter.
820: Convolves the input image with
821: the kernel
822: .P1 20n
823: 0 -1 0
824: -1 5 -1
825: 0 -1 0
826: .P2
827: This is a fairly extreme high-pass filter.
828: .TP "median [\fIpicture\fP]
829: 3\(mu3 median filter. Each pixel is replaced by the
830: median of the 3\(mu3 window surrounding it.
831: .TP "smooth [\fIpicture\fP]
832: 3\(mu3 Bartlett filter.
833: Convolves the input image with
834: the kernel
835: .P1 20n
836: 1/16 2/16 1/16
837: 2/16 4/16 2/16
838: 1/16 2/16 1/16
839: .P2
840: This is a moderately strong low-pass filter.
841: .TP "3to1 [-e] \fIcolormap\fP [\fIpicture\fP]
842: Converts the input picture from full-color (\fTrgb\fP) to a single
843: channel mapping each pixel to the closest entry of
844: .I colormap .
845: .TP "mcut [\fIpicture\fP]
846: Reads a picture, and writes a color map on standard output suitable for use by
847: .I 3to1 .
848: .I Mcut
849: uses Heckbert's median-cut algorithm to pick a color map that
850: matches
851: .I picture 's
852: colors pretty well.
853: .TP "improve \fIcolormap\fP [\fIpicture\fP]
854: Given a color map and a picture file, this outputs a new color map
855: that better represents the colors of the picture. The algorithm
856: is to output the centroid of those pixel values that are closest
857: to each input color map entry. Running
858: .I improve
859: several times may produce better and better color maps.
860: .TP "quantize [\fIpicture\fP]
861: Convert a full-color picture to an 8-bit picture with color map.
862: This is just a command file that calls
863: .I mcut ,
864: .I improve
865: and
866: .I 3to1 .
867: It does a much better job than
868: .I dither .
869: .TP "remap \fIcolormap\fP [\fIpicture\fP]
870: The input picture should be full color (\fTCHAN=rgb\fP).
871: The output will have its pixel values will be altered
872: so that when mapped through the given
873: .I colormap
874: they will be as close as possible to the input's pixel
875: values.
876: .TP "resample \fIwidth\fP [\fIpicture\fP] [\fIB C\fP]
877: Resample the input image to be
878: .I width
879: pixels wide.
880: The default filter used in resampling minimizes both
881: pre- and post-aliasing.
882: Numeric parameters
883: .I B
884: and
885: .I C
886: (both default to 1/3)
887: pick the resampling kernel from a Mitchell and Netravali's two-parameter
888: family of piecewise cubic kernels.
889: .TP "transpose [-vhadrlui] [-o \fIx y\fP] [\fIpicture\fP]
890: Transpose the input picture. This is useful in conjunction with
891: commands that operate on scan-lines, like
892: .I resample ,
893: to perform operations on columns instead of rows.
894: Under control of its options,
895: .I transpose
896: can perform any symmetry operation of the integer lattice.
897: The
898: .CW -v
899: option reflects through a vertical line.
900: The
901: .CW -h
902: option reflects through a horizontal line.
903: The
904: .CW -a
905: option reflects through an ascending diagonal line.
906: The
907: .CW -d
908: option reflects through a descending diagonal line
909: (the default).
910: The
911: .CW -r
912: option rotates right (clockwise 90 degrees).
913: The
914: .CW -l
915: option rotates left (counterclockwise 90 degrees).
916: The
917: .CW -u
918: option flips the image upside down (180 degree rotation.)
919: For completeness, the
920: .CW -i
921: option does the identity transformation.
922: The
923: .CW -o
924: option translates the picture, adding
925: .I x,y ) (
926: to all coordinates. Without this option, the upper-left
927: corner of the image's window does not change.
928: .TP "shear \fIangle\fP [\fIpicture\fP]
929: Rotate the input image by the given
930: .I angle
931: (in degrees). It's called
932: .I shear
933: because it operates by shearing the image 3 times
934: (horizontally, then vertically, then horizontally).
935: .TP "lx [-o\fIfile\fP] [-A\fIaspect\fP] [-a] [-s\fIscale\fP] [-r\fIrot\fP] [-x\fIxscale\fP] [-y\fIyscale\fP] [\fIpicture\fP]
936: Perform a linear transformation on the input image.
937: The
938: .CW -o
939: option specifies the output file name. The default is standard output.
940: The
941: .CW -A
942: option specifies the aspect ratio of the pixels. The default is 1.
943: The ITI frame-grabber produces images whose pixel aspect-ratio is 1.25.
944: The
945: .CW -a
946: option suppresses the writing of an alpha channel. Normally
947: an alpha channel is computed even for input images that don't have one,
948: since the output picture is often rotated and thus doesn't completely
949: cover its window.
950: .IP
951: The transformation is specified by a sequence of options. The specified
952: transformations are combined in the order given to yield a composite transformation.
953: The relevant options are:
954: .nf
955: .ta 8n
956: \fT-s\fIscale\fR scale by \fIscale\fR.
957: \fT-r\fIrot\fR rotate by \fIrot\fR degrees clockwise.
958: \fT-x\fIxscale\fR scale in x by \fIxscale\fR.
959: \fT-y\fIyscale\fR scale in y by \fIyscale\fR.
960: .PP
961: There are several commands to generate images from
962: three-dimensional geometric descriptions of various sorts.
963: Most of these produce
964: .CW CHAN=rgbaz...
965: images that may be combined using
966: .I 3matte .
967: In their output files, points at the near clipping plane will be mapped to
968: points having
969: .I z=0 ,
970: and points at the far clipping plane will have
971: .I z=1 .
972: .TP "ncpr [-a \fIaspect\fT] [-w \fIx0 y0 x1 y1\fT] [-c \fIrgbaz\fT] \fIinput\fT [\fIoutput\fT]
973: New Cheezy Polygon Renderer.
974: .I Output
975: (default standard output) is the name of the picture file that will contain the rendered
976: version of the scene described in
977: .I input ,
978: a text file specifying a polygonal scene.
979: The
980: .CW -a
981: option sets the pixel aspect-ratio (default 1.)
982: The
983: .CW -w
984: option sets the window of the output picture.
985: The
986: .CW -c
987: option specifies which channels should be written to the output picture.
988: .IP
989: The input file contains a sequence of single-letter commands, each with several
990: numeric parameters. The commands are:
991: .IP
992: \fTv \fIfov near far ex ey ez lx ly lz ux uy uz\fR
993: .br
994: Set viewing parameters.
995: .I Fov
996: is the angle subtended vertically by the screen at the eye point.
997: Points whose distance from the eye is not between
998: .I near
999: and
1000: .I far
1001: will be clipped away before drawing. However tempted, do not set
1002: .I near
1003: to zero, lest underflow or divide-check occur.
1004: .I ex,ey,ez ) (
1005: is the coordinate of the eye, the point from which the scene is viewed
1006: and the center of perspective.
1007: .I lx,ly,lz ) (
1008: is a vector pointing from the eye toward the center of the scene.
1009: The point
1010: .I lx+ex,ly+ey,lz+ez ) (
1011: is mapped into the center of the screen.
1012: .I ux,uy,uz ) (
1013: is the up vector, the direction of the zenith. The point
1014: .I lx+ux,ly+uy,lz+uz ) (
1015: is mapped into a point somewhere above the center of the screen.
1016: .IP
1017: \fTl \fIx y z\fR
1018: .br
1019: Set the direction of the light source to
1020: .I x,y,z ). (
1021: The light source is ``at infinity'' in the given direction.
1022: .IP
1023: \fTb \fIred green blue alpha\fR
1024: Clear the screen to the given color.
1025: .I Red ,
1026: .I green ,
1027: .I blue
1028: and
1029: .I alpha
1030: should all be between 0 and 255.
1031: .IP
1032: \fTc \fIindex red green blue alpha\fR
1033: Set a color table entry. Indices into the color table are used
1034: to specify the colors of polygons (see below.)
1035: The table has 500 entries. Unless reloaded by the
1036: .CW c
1037: command, the first 256 entries contain the 256 shades of gray,
1038: the following 12 entries (256-267) are set to 12 logarithmically
1039: spaced (perceptually equal) gray shades, and the next 20 entries
1040: (268-287) to 20 logarithmically spaced gray shades.
1041: .IP
1042: \fTt \fIx0 y0 z0 x1 y1 z1 x2 y2 z2 c0 c1\fR
1043: .br
1044: Render a triangle with vertices
1045: .I x0,y0,z0 ), (
1046: .I x1,y1,z1 ) (
1047: and
1048: .I x2,y2,z2 ). (
1049: The side the normal (calculated using the right hand rule) out of has color
1050: .I c0 ,
1051: on the other it is
1052: .I c1 .
1053: If
1054: .I c0
1055: or
1056: .I c1
1057: is positive, the polygon's color is found in the corresponding color
1058: table entry. If negative, the color is found by modifying the color
1059: table entry as though the surface were illuminated by a light source
1060: whose direction was specified by the
1061: .CW l
1062: command.
1063: .IP
1064: \fTp \fIc0 c1 x0 y0 z0 x1 y1 z1 ... xn yn zn \fT;\fR
1065: .br
1066: Render a polygon whose color is
1067: .I c0
1068: on one side and
1069: .I c1
1070: on the other.
1071: The polygon's vertices are
1072: .I x0,y0,z0 ), (
1073: .I x1,y1,z1 ), (
1074: \&...,
1075: .I xn,yn,zn ). (
1076: .in -8n
1077: .TP "quad [-a] [-z] [-w \fIx0 y0 x1 y1\fP] \fIin out
1078: .br
1079: Compute an image of a quadric surface. The
1080: .CW -a
1081: option suppresses writing out the alpha channel.
1082: The
1083: .CW -z
1084: option suppresses writing out the z channel.
1085: The
1086: .CW -w
1087: option specifies the output window.
1088: The input file should contain 34 floating point numbers.
1089: The first ten numbers are the upper triangle of the symmetric
1090: matrix describing the quadratic form (in screen coordinates.)
1091: The next 16 numbers are a matrix that converts screen-space
1092: coordinates into world-space normals for illumination computations.
1093: The next three numbers are the direction of the light source.
1094: The next four numbers are the red, green, blue and alpha of the
1095: surface's color. The last number is the amount of ambient light
1096: in the environment.
1097: .TP "terrain \fIin out ex ey ez lx ly fov near far
1098: Render a terrain image.
1099: The input file
1100: is a 2-channel picture file containing 16-bit elevation data on a regular grid.
1101: .I ex,ey,ez ) (
1102: is the eye position.
1103: .I lx,ly,0 ) (
1104: is a vector pointing from the eye to the center of the scene.
1105: The up direction is
1106: .I 0,0,1 ). (
1107: .I Fov
1108: is the vertical field-of-view angle.
1109: .I Near
1110: and
1111: .I far
1112: are the distances from the eye to the near and far clipping planes.
1113: .TP "bg \fIr0 g0 b0 r1 g1 b1 out
1114: Generate a background card whose color varies smoothly
1115: from
1116: .I r0,g0,b0 ) (
1117: at the top to
1118: .I r1,g1,b1 ) (
1119: at the top.
1120: Its z coordinate is set to 2, which is beyond the far clipping plane.
1121: .TP "aplot [-t \fItype\fP] [-r \fIrange\fP] [-w \fIx0 y0 x1 y1\fP] \fIinput
1122: Produces an anti-aliased isometric plot of a square array of binary data, read from
1123: its input file.
1124: The
1125: .CW -r
1126: option specifies the maximum absolute value of the data.
1127: This may be adjusted to affect the height of the highest peaks in the plot.
1128: By default, the input is examined to find its range.
1129: The
1130: .CW -w
1131: option specifies the window in which the plot will be drawn.
1132: The data file is just a binary dump of a square array.
1133: It has no header, and in particular is not a picture file.
1134: The
1135: .CW -t
1136: option (default
1137: .CW -tf)
1138: specifies the type of data in the array.
1139: .KS
1140: .TS
1141: center;
1142: c c
1143: aFCW a.
1144: _
1145: option type
1146: =
1147: -tf float
1148: -ts short int
1149: -ti int
1150: -tl long int
1151: -td double
1152: -tc char
1153: -tu unsigned char
1154: _
1155: .TE
1156: .KE
1157: .NH
1158: Animation
1159: .PP
1160: To use a command-based raster graphics system as described here to
1161: for animation requires writing command files to create and record
1162: long sequences of images. Typical command files contain long sequences
1163: of repeated commands with slowly changing numeric parameters. Several
1164: sequences starting and ending at different times may be interleaved
1165: to describe overlapping motion. They are at best tedious and at worst
1166: tricky to generate by hand or using the usual tools.
1167: .PP
1168: .I Moto
1169: is a command generator tailored for an animator's needs. Its input is
1170: a concise description of the animation to be performed; its output is
1171: a command file suitable for input to
1172: .I sh ,
1173: .I rc
1174: or some other command interpreter.
1175: Its arguments are an optional file name containing a
1176: .I moto
1177: program (default standard input) and list of numeric parameters
1178: that are made available to the program.
1179: .PP
1180: A
1181: .I moto
1182: program consists of a list of groups of commands. Each block is
1183: guarded by a range of frames. Here is an example:
1184: .P1
1185: 1,5: pcp this %0
1186: pcp %0 that
1187: .P2
1188: This generates
1189: .P1
1190: pcp this %0
1191: pcp %0 that
1192: pcp this %0
1193: pcp %0 that
1194: pcp this %0
1195: pcp %0 that
1196: pcp this %0
1197: pcp %0 that
1198: pcp this %0
1199: pcp %0 that
1200: .P2
1201: The command group is repeated for each of frames 1 to 5.
1202: .PP
1203: Groups may contain parameter ranges enclosed in brackets
1204: .CW [] :
1205: .P1
1206: 1,5: pcp frame.[1,5] %0
1207: echo snap|2500
1208: .P2
1209: This generates:
1210: .P1
1211: pcp frame.1 %0
1212: echo snap|2500
1213: pcp frame.2 %0
1214: echo snap|2500
1215: pcp frame.3 %0
1216: echo snap|2500
1217: pcp frame.4 %0
1218: echo snap|2500
1219: pcp frame.5 %0
1220: echo snap|2500
1221: .P2
1222: .PP
1223: Programs may have multiple groups, each guarded by
1224: a separate range of frames. For each frame,
1225: .I moto
1226: checks each group and processes those
1227: whose guards include the current frame number.
1228: .PP
1229: Two special guards,
1230: .CW BEGIN
1231: and
1232: .CW END ,
1233: specify actions to be taken before an after processing frames:
1234: .P1
1235: BEGIN: clr
1236: 1,5: pcp section[1,5] %0
1237: END: pcp %0 composite
1238: .P2
1239: This generates
1240: .P1
1241: clr
1242: pcp section1 %0
1243: pcp section2 %0
1244: pcp section3 %0
1245: pcp section4 %0
1246: pcp section5 %0
1247: pcp %0 composite
1248: .P2
1249: .LP
1250: .I Moto
1251: allows complex computations inside parameter brackets:
1252: .P1 0
1253: 1,10: clr [127.5*(1-cos([0,360]))]
1254: .P2
1255: This generates
1256: .P1
1257: clr 0
1258: clr 29.82933350233
1259: clr 105.35985734747
1260: clr 191.25
1261: clr 247.3108091502
1262: clr 247.3108091502
1263: clr 191.25
1264: clr 105.35985734747
1265: clr 29.82933350233
1266: clr 0
1267: .P2
1268: .PP
1269: Expressions may include constants and variables.
1270: All values are double-precision floating point numbers.
1271: The operators
1272: .CW = ,
1273: .CW / ,
1274: .CW + ,
1275: .CW -
1276: (both unary and binary),
1277: .CW < ,
1278: .CW > ,
1279: .CW <= ,
1280: .CW >= ,
1281: .CW == ,
1282: .CW != ,
1283: .CW "? :"
1284: and
1285: .CW ! ,
1286: all with their meanings as in C, except that all results
1287: are coerced to
1288: .CW double .
1289: The result of
1290: .CW a%b
1291: is
1292: .CW a-b*(int)(a/b) .
1293: The result of
1294: .CW "a && b
1295: is
1296: .CW "a?b:a .
1297: The result of
1298: .CW "a || b
1299: is
1300: .CW "a?a:b .
1301: The exponentiation operator is
1302: .CW ^ ,
1303: also written
1304: .CW ** .
1305: The expression
1306: .CW [a,b]
1307: varies from
1308: .CW a
1309: to
1310: .CW b ,
1311: linearly as the frame number varies between the guards of the
1312: group containing the expression.
1313: The expression
1314: .CW a[b,c]
1315: has the value
1316: .CW a*b+(1-a)*c .
1317: Its value varies from
1318: .CW b
1319: to
1320: .CW c
1321: as
1322: .CW a
1323: varies from 0 to 1.
1324: The expression
1325: .CW $i
1326: has the value of the
1327: .CW i 'th
1328: parameter following the file name on
1329: .I moto 's
1330: command line.
1331: .PP
1332: The precedence of operators is, from lowest to highest:
1333: .P1
1334: =
1335: ? :
1336: ||
1337: &&
1338: < <= == != > >=
1339: + -
1340: * / %
1341: [ ]
1342: ^ **
1343: - \fR(unary)\fP ! $
1344: .P2
1345: Expressions may be parenthesized to alter precedence.
1346: .SP 10
1347: ...........
1348: .PP
1349: The following math functions are available:
1350: .KS
1351: .TS
1352: center;
1353: lFCW lFCW lFCW lFCW.
1354: acos besy0 exp log10
1355: asin besy1 fabs sin
1356: atan besyn floor sinh
1357: besj0 ceil gamma sqrt
1358: besj1 cos hypot tan
1359: besjn cosh log tanh
1360: .TE
1361: .KE
1362: All math functions are as described in the C library,
1363: except that angles are measured in degrees rather than
1364: radians for the trig and inverse trig functions.
1365: In addition
1366: .I hypot
1367: may have two or three arguments,
1368: .I atan
1369: may take two arguments instead of one,
1370: and may also be spelled
1371: .I atan2 .
1372: .PP
1373: For parameterization, and to allow even more complex
1374: computations,
1375: .I moto
1376: has variables, assignment and computation groups.
1377: A computation group is distinguished from a command group
1378: by having a double colon separating its guard from the
1379: expressions to be computed:
1380: .P1 0
1381: BEGIN:: n=5
1382: 1,n:: x=512*sin([0,90])
1383: 1,n: pcp -w 0 0 [x] 488 pic.[1,n] %0
1384: .P2
1385: This generates
1386: .P1 0
1387: pcp -w 0 0 0 488 pic.1 %0
1388: pcp -w 0 0 195.93391737093 488 pic.2 %0
1389: pcp -w 0 0 362.03867196751 488 pic.3 %0
1390: pcp -w 0 0 473.02632064578 488 pic.4 %0
1391: pcp -w 0 0 512 488 pic.5 %0
1392: .P2
1393: .1C
1394: .KF bottom
1395: .sp 4
1396: .P1
1397: BEGIN:: nchase=108
1398: nrun=195
1399: d1=12
1400: d2=32
1401: end=nrun+d2
1402: chase=end-nchase+1
1403: 1,end: inputs= # empty the input list
1404: 1,nrun: inputs="$inputs run.[1,nrun]" # add the first saucer to the input list
1405: 1+d1,nrun+d1:
1406: inp="$inputs run.[1,nrun]" # add the second saucer
1407: chase,end:
1408: inp="$inputs chase.[1,nchase]" # add the chasing saucer
1409: 1,end:
1410: 3matte -a $inp bg frame.[1,end] # create the composite
1411: .P2
1412: .SP
1413: .ce
1414: \fBFigure 1.\fP Flying saucer script
1415: .KE
1416: .2C
1417: .PP
1418: Upon occasion it is useful to split
1419: .I moto 's
1420: output into several files, under program control.
1421: A group that is separated from its guards by an at-sign
1422: .CW @
1423: instead of a colon names a file into which
1424: subsequent output is to be written. For example,
1425: .P1
1426: 1,5@ file.[1,5]
1427: 1,5: This is file.[1,5].
1428: .P2
1429: creates 5 files, with names
1430: \fTfile.1\fR,...,\fTfile.5\fR.
1431: Each file's contents will announce its name.
1432: .PP
1433: As is true for all sufficiently large programs,
1434: .I moto
1435: has a shell escape. A group separated from its
1436: guards by an exclamation point
1437: .CW !
1438: instead of a colon has its result text interpreted
1439: by a subshell.
1440: .PP
1441: Finally, Figure 1 shows an example taken from a real application.
1442: This
1443: .I moto
1444: program composites the frames of a short movie showing
1445: two flying saucers, flying in formation, chased by a third,
1446: racing over New Jersey. The flying
1447: saucer images (files
1448: .CW run.*
1449: and
1450: .CW chase.* )
1451: and the background (file
1452: .CW bg )
1453: have been computed in advance. In the composite, the
1454: .CW run.*
1455: images are re-used, staggered in time, to do the
1456: first two saucers.
1457: .NH
1458: References
1459: .PP
1460: |reference_placement
1461: .BP
1462: photo page
1463: .BP
1464: divider with title
1465: .sp
1466: .ce
1467: Implementation and Maintenance
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