Video on Oscilloscope (Easy!)

Here is the easiest way to put video on an old analog oscilloscope that has "Z axis" inputs (usually on the back of the scope:

It uses an LM1881 integrated chip and nine other little components to display live video on an oscilloscope screen.

You'll need the following:

(3) 0.1uF caps

(1) 4.7Uf cap

(1) 1000pF cap

(1) 680k resistor

(2) 100k resistors

(1) LM1881 chip

(2) IN4148 diodes

Plus: an oscilloscope with a Z input; a video camera with a composite video out (usually a yellow RCA plug); two thin wires to go to Z input; a DC power supply that can be adjustable to +5vDC (you'll probably need around 3-4vDC); a composite RCA cable to run from camera to circuit; a breadboard or soldering iron; breadboard jumper cables; wires from power supply.

Here's my version on a breadboard. It's only 10 components but I used a lot of jumper cables to keep things simpler for me to see.

Below is a drawing of the end of the RCA cable coming from the video camera (or TV or VCR or DVD player or videogame console, etc.). The pointy tip is the positive signal. When you're all done you could run a ground wire from the ring/barrel negative part of the RCA plug--but I found it made zero difference on or off, so I'd leave it off.

You'll see nothing until you hook up the wires to the Z axis (intensity) of the oscilloscope. The picture was black and green, upside down and mirror-image flipped. I pointed the video camera at a TV set. Here is a Voltoren medicine commercial.

This photo is of a episode of The Three Stooges. It's hard to see in the photo, but it's the episode where Larry dresses in lady's clothing and tries to seduce members of the Nazi Upper Eschelon. Shown is "Admiral Boring" (Goering) giving the Hitler-salute to Reich's-Fuhrer Moe! It was a weird episode.

User caveats:

1. Use XY mode on the oscilloscope. 

2. The black (negative) bands of the diodes should be closer to the LM1881 in the circuit path.

3. Z axis are not reversed, like other versions of this circuit in books. Z Axis + goes to the center pin tip of the RCA plug. Z Axis - goes to the ring/barrel/negative/ground of the RCA plug. When I reversed them I got no picture.

4. The camera (mine was a 1980s JVC) had to be "zoomed in" for this to work. I don't know why! If I zoomed out to wide-angle the circuit stopped working.

5. You only get a small portion of the video that the video camera sees!

6. I set the video camera exposure control to "+" for a brighter image.

7. With 3.6vDC to 4.1vDC I had much less noise in the video than running at 5vDC. Fiddle with the voltage.

8. The oscilloscope probes I used are newer ones that have 1x and 10x. Use the 1x setting, it got a much better signal for this usage. If your probes don't have a switch on them--they're probably 1x anyway.

Some random shots of my self-assembled Elenco kit power supply (from Amazon or eBay). My $5 HP analog oscilloscope from an antiques store/resale shop. The settings on the scope aren't exactly what I ended up using, but they're in the ballpark. As you can see my X and Y are actually A and B on the scope! There's also an unused horizontal input. The "Z axis" is in the back of this scope: so I ran two wires to the two screws in the back and have them wrapped around the front handle for easy access (instead of reaching behind this super heavy scope all the time).

I set the inputs to "DC" which gave a better image. I think "AC" worked by spread out the the signal and made it way worse. The "BW limit" was off (made a small difference). X vs Y setting. Scope was set to "CONV" which is the normal display setting on this scope (your scope probably won't even have that option). In the end my X and Y (or A and B) were BOTH set to ".2" on the knobs.

In the end I realized my dream of watching an episode of Columbo in Black and Green on an oscilloscope. My bucket list (other buying a new 2021 Ford Bronco) is pretty much complete.

This is one of the chickens that rampaged all over the neighborhood:

                                                                           Delicious!

STRANGE ATTRACTORS + BASIC CODING

 

More fun with BASIC and Strange Attractors...

 

This combines two things I’ve been playing with: Strange Attractors (previously via oscilloscopes and oscillating circuits); and BASIC computer language (via a download of Rob Hagemans’ awaesome PC-BASIC emulator, which loaded on my 2020 HP Prodesk just fine: https://robhagemans.github.io/pcbasic/ ).

 

The first program, which comes from Julien Sprott’s “Strange Attractors” book (1993) wouldn’t work at all for me, because it had no callouts in the BASIC programming for video display. I solved that by FINALLY figuring out/remembering I needed to set the display to something my modern computer could use while using an emulator.

 

If you run this program and get an error code about line 1350 make sure to set your video to something the emulator can deal with. So, run the program. Did you get the error code? Type in “SCREEN 9” which will change the screen resolution in the BASIC emulator and all of a sudden it works! You can try lower numbers than 9.

If you find a number that works you could actually add it to the program AFTER line 1010. So it would be like “1011 SCREEN 9”. I didn’t add it to the program below so you could play around and see what video mode works for your setup. I tried adding it before the DEFDBL A-Z statement and it didn’t work (make it a number after 1010 but before 1020).

 

Remember, after cutting and pasting the code into your emulator (using ctrl+c to copy off of here, but using F11+V to paste in the emulator) you must type SCREEN 9 if you get a “1350 error”. Then just type "run" again.

 

1010 DEFDBL A-Z

1020 DIM XS(499)

1030 SM% = 12

1040 PREV% = 2

1050 NMAX = 11000

1160 RANDOMIZE TIMER

1190 GOSUB 1300

1200 GOSUB 1500

1210 GOSUB 1700

1220 GOSUB 2100

1230 GOSUB 2400

1240 ON T% GOTO 1190, 1200, 1210

1250 CLS

1260 END

1300 REM INITIALIZE

1350 WINDOW (-.1, -.1)-(1.1, 1.1)

1360 CLS : LOCATE 13, 44: PRINT "MIKE LOGUSZ"

1420 RETURN

1500 REM SET PARAMETERS

1510 X = .05

1560 R = 4

1570 T% = 3

1580 P% = 0

1590 LINE (-.1, -.1)-(1.1, 1.1),,B

1630 RETURN

1700 REM ITERATE EQUATIONS

1720 XNEW = R * X * (1 - X)

2030 RETURN

2100 REM DISPLAY RESULTS

2210 XS(P%) = X

2220 P% = (P% + 1) MOD 500

2230 I% = (P% + 500 - PREV%) MOD 500

2300 PSET (XS(I%), XNEW)

2320 RETURN

2400 REM TEST RESULTS

2490 IF LEN (INKEY$) THEN T% = O

2510 X = XNEW

2550 RETURN

The 1040 PREV% = 2 line is the iterations (humps) in the wave. You can use 1-10. Starting here is 2, you should try 5 next. The higher you go the slower everything is. It gets boring. The photo shows line 1040 set to "5".

 

The 1360 can be changed to put your name on the screen. The "44" number on that line is what makes the name over to the right. Try making it a "34" and center it better if you like.

 

In the program above I've already made changes that incorporate the following caveats from author Julein Sprott:

"Line 1010: Be sure your version of BASIC supports double-precision (four-byte) floating-point variables. If it doesn't you may omit this line but you will then probably have to change the 4 in line 1560 to 3.99999 to avoid overflow resulting from round-off errors. With modern versions of BASIC and a computer with a math coprocessor there is no penalty and considerable advantage in using double precision. Because of the finite precision of computer arithmetic all cases will eventually repeat but with double precision the average number of iterations required before this happens is acceptably large.

Line 1320: Either your version of BASIC doesn't require this command or your computer or compiler doesn't support VGA graphics. Try reducing the 12 in line 1030 to a lower number until you find one that works. If none work try eliminating line 1320 altogether.

Line 1350: The WINDOW command defines the coordinates of the lower-left and upper-right corners of the graphics window for subsequent PSET and LINE commands. If your version of BASIC doesn't support this command you will have to delete this line and convert all the parameters in the PSET and LINE commands to address screen pixels. In such a case try replacing line 2300 with PSET (200 * X 200 - 200 * XNEW). One advantage of using the WINDOW command is that when a version of BASIC comes along that supports higher screen resolutions the program can be easily recompiled to take advantage of it."

You can do/undo these if you wish. Search "Strange Attractors" by Sprott for a cool author's website with html, word Doc and PDF versions of the book for free! Ebay also has copies of this book with the original (floppy) discs included--that also has other versions besides BASIC! Or just check out the word Doc from the author's site. The html has scanning errors/omissions and the PDF might too. I found fixes at the Word Doc versions. Check all three!

In the above I've done program 1 + program 2 + the fixes + my own little fix to the book's coding. Program 1 would give you just a single parabola instead of awesome chaos without the iterations of the 1040 line (introduced as program 2).

More Chaos!!! Even Stranger Attractors!!!!

Here is the program for up to fourth-dimension attractors with colors and different map surfaces (plane, sphere, torus, etc.). It seems to work just fine graphically without having to mess with anything like SCREEN 9 because the 1020 line is better and works with other lines of code to make the screen OK, at least in my emulator on my machine.

 

The additional lines of code (a lot) bring into the search for chaos quadratic equations, fractals, Henon maps, cubic and quartic and quintic maps, project onto various planes and surfaces, and can even use sound to express the results (see line of code 3500)! 

1010 DEFDBL A-Z                 'Use double precision

1020 DIM XS(499), YS(499), ZS(499), WS(499), A(504), V(99), XY(4), XN(4), COLR%(15)

1030 SM% = 12                   'Assume VGA graphics

1040 PREV% = 5                  'Plot versus fifth previous iterate

1050 NMAX = 11000               'Maximum number of iterations

1060 OMAX% = 5                  'Maximum order of polynomial

1070 D% = 2                     'Dimension of system

1080 EPS = .1                   'Step size for ODE

1090 ODE% = 0                   'System is map

1100 SND% = 0                   'Turn sound off

1110 PJT% = 0                   'Projection is planar

1120 TRD% = 1                   'Display third dimension as shadow

1130 FTH% = 2                   'Display fourth dimension as colors

1140 SAV% = 0                   'Don't save any data

1150 TWOPI = 6.28318530717959#  'A useful constant (2 pi)

1160 RANDOMIZE TIMER            'Reseed random number generator

1170 GOSUB 4200                 'Display menu screen

1180 IF Q$ = "X" THEN GOTO 1250 'Exit immediately on command

1190 GOSUB 1300                 'Initialize

1200 GOSUB 1500                 'Set parameters

1210 GOSUB 1700                 'Iterate equations

1220 GOSUB 2100                 'Display results

1230 GOSUB 2400                 'Test results

1240 ON T% GOTO 1190, 1200, 1210

1250 CLS

1260 END

 

1300 REM Initialize

1310 ON ERROR GOTO 6600         'Find legal graphics mode

1320 SCREEN SM%                 'Set graphics mode

1330 ON ERROR GOTO 0            'Resume default error trapping

1340 DEF SEG = 64: WID% = PEEK(74)  'Number of text columns

1350 WINDOW (-.1, -.1)-(1.1, 1.1)

1360 CLS : LOCATE 13, WID% / 2 - 6: PRINT "Searching Logusz..."

1370 GOSUB 5600                 'Set colors

1380 IF QM% <> 2 THEN GOTO 1420

1390    NE = 0: CLOSE

1400    OPEN "SA.DIC" FOR APPEND AS #1: CLOSE

1410    OPEN "SA.DIC" FOR INPUT AS #1

1420 RETURN

 

1500 REM Set parameters

1510 X = .05                    'Initial condition

1520 Y = .05

1530 Z = .05

1540 W = .05

1550 XE = X + .000001: YE = Y: ZE = Z: WE = W

1560 GOSUB 2600                 'Get coefficients

1570 T% = 3

1580 P% = 0: LSUM = 0: N = 0: NL = 0: N1 = 0: N2 = 0

1590 XMIN = 1000000!: XMAX = -XMIN: YMIN = XMIN: YMAX = XMAX

1600 ZMIN = XMIN: ZMAX = XMAX

1610 WMIN = XMIN: WMAX = XMAX

1620 TWOD% = 2 ^ D%

1630 RETURN

 

1700 REM Iterate equations

1710 IF ODE% > 1 THEN GOSUB 6200: GOTO 2020     'Special function

1720 M% = 1: XY(1) = X: XY(2) = Y: XY(3) = Z: XY(4) = W

1730 FOR I% = 1 TO D%

1740 XN(I%) = A(M%)

1750 M% = M% + 1

1760 FOR I1% = 1 TO D%

1770 XN(I%) = XN(I%) + A(M%) * XY(I1%)

1780 M% = M% + 1

1790 FOR I2% = I1% TO D%

1800 XN(I%) = XN(I%) + A(M%) * XY(I1%) * XY(I2%)

1810 M% = M% + 1

1820 IF O% = 2 THEN GOTO 1970

1830 FOR I3% = I2% TO D%

1840 XN(I%) = XN(I%) + A(M%) * XY(I1%) * XY(I2%) * XY(I3%)

1850 M% = M% + 1

1860 IF O% = 3 THEN GOTO 1960

1870 FOR I4% = I3% TO D%

1880 XN(I%) = XN(I%) + A(M%) * XY(I1%) * XY(I2%) * XY(I3%) * XY(I4%)

1890 M% = M% + 1

1900 IF O% = 4 THEN GOTO 1950

1910 FOR I5% = I4% TO D%

1920 XN(I%) = XN(I%) + A(M%) * XY(I1%) * XY(I2%) * XY(I3%) * XY(I4%) * XY(I5%)

1930 M% = M% + 1

1940 NEXT I5%

1950 NEXT I4%

1960 NEXT I3%

1970 NEXT I2%

1980 NEXT I1%

1990 IF ODE% = 1 THEN XN(I%) = XY(I%) + EPS * XN(I%)

2000 NEXT I%

2010 M% = M% - 1: XNEW = XN(1): YNEW = XN(2): ZNEW = XN(3): WNEW = XN(4)

2020 N = N + 1

2030 RETURN

 

2100 REM Display results

2110 IF N < 100 OR N > 1000 THEN GOTO 2200

2120    IF X < XMIN THEN XMIN = X

2130    IF X > XMAX THEN XMAX = X

2140    IF Y < YMIN THEN YMIN = Y

2150    IF Y > YMAX THEN YMAX = Y

2160    IF Z < ZMIN THEN ZMIN = Z

2170    IF Z > ZMAX THEN ZMAX = Z

2180    IF W < WMIN THEN WMIN = W

2190    IF W > WMAX THEN WMAX = W

2200 IF N = 1000 THEN GOSUB 3100        'Resize the screen

2210 XS(P%) = X: YS(P%) = Y: ZS(P%) = Z: WS(P%) = W

2220 P% = (P% + 1) MOD 500

2230 I% = (P% + 500 - PREV%) MOD 500

2240 IF D% = 1 THEN XP = XS(I%): YP = XNEW ELSE XP = X: YP = Y

2250 IF N < 1000 OR XP <= XL OR XP >= XH OR YP <= YL OR YP >= YH THEN GOTO 2320

2260    IF PJT% = 1 THEN GOSUB 4100     'Project onto a sphere

2270    IF PJT% = 2 THEN GOSUB 6700     'Project onto a horizontal cylinder

2280    IF PJT% = 3 THEN GOSUB 6800     'Project onto a vertical cylinder

2290    IF PJT% = 4 THEN GOSUB 6900     'Project onto a torus

2300    GOSUB 5000                      'Plot point on screen

2310    IF SND% = 1 THEN GOSUB 3500     'Produce sound

2320 RETURN

 

2400 REM Test results

2410 IF ABS(XNEW) + ABS(YNEW) + ABS(ZNEW) + ABS(WNEW) > 1000000! THEN T% = 2

2420 IF QM% = 2 THEN GOTO 2490  'Speed up evaluation mode

2430 GOSUB 2900                 'Calculate Lyapunov exponent

2440 GOSUB 3900                 'Calculate fractal dimension

2450 IF QM% > 0 THEN GOTO 2490  'Skip tests when not in search mode

2460 IF N >= NMAX THEN T% = 2: GOSUB 4900   'Strange attractor found

2470 IF ABS(XNEW - X) + ABS(YNEW - Y) + ABS(ZNEW - Z) + ABS(WNEW - W) < .000001 THEN T% = 2

2480 IF N > 100 AND L < .005 THEN T% = 2    'Limit cycle

2490 Q$ = INKEY$: IF LEN(Q$) THEN GOSUB 3600        'Respond to user command

2500 IF SAV% > 0 THEN IF N > 1000 AND N < 17001 THEN GOSUB 7000 'Save data

2510 X = XNEW                   'Update value of X

2520 Y = YNEW

2530 Z = ZNEW

2540 W = WNEW

2550 RETURN

 

2600 REM Get coefficients

2610 IF QM% <> 2 THEN GOTO 2640 'Not in evaluate mode

2620    IF EOF(1) THEN QM% = 0: GOSUB 6000: GOTO 2640

2630    IF EOF(1) = 0 THEN LINE INPUT #1, CODE$: GOSUB 4700: GOSUB 5600

2640 IF QM% > 0 THEN GOTO 2730  'Not in search mode

2650    O% = 2 + INT((OMAX% - 1) * RND)

2660    CODE$ = CHR$(59 + 4 * D% + O% + 8 * ODE%)

2670    IF ODE% > 1 THEN CODE$ = CHR$(87 + ODE%)

2680    GOSUB 4700              'Get value of M%

2690    FOR I% = 1 TO M%        'Construct CODE$

2700        GOSUB 2800          'Shuffle random numbers

2710        CODE$ = CODE$ + CHR$(65 + INT(25 * RAN))

2720    NEXT I%

2730 FOR I% = 1 TO M%           'Convert CODE$ to coefficient values

2740    A(I%) = (ASC(MID$(CODE$, I% + 1, 1)) - 77) / 10

2750 NEXT I%

2760 RETURN

 

2800 REM Shuffle random numbers

2810 IF V(0) = 0 THEN FOR J% = 0 TO 99: V(J%) = RND: NEXT J%

2820 J% = INT(100 * RAN)

2830 RAN = V(J%)

2840 V(J%) = RND

2850 RETURN

 

2900 REM Calculate Lyapunov exponent

2910 XSAVE = XNEW: YSAVE = YNEW: ZSAVE = ZNEW: WSAVE = WNEW

2920 X = XE: Y = YE: Z = ZE: W = WE: N = N - 1

2930 GOSUB 1700                 'Reiterate equations

2940 DLX = XNEW - XSAVE: DLY = YNEW - YSAVE

2950 DLZ = ZNEW - ZSAVE: DLW = WNEW - WSAVE

2960 DL2 = DLX * DLX + DLY * DLY + DLZ * DLZ + DLW * DLW

2970 IF CSNG(DL2) <= 0 THEN GOTO 3070       'Don't divide by zero

2980    DF = 1000000000000# * DL2

2990    RS = 1 / SQR(DF)

3000    XE = XSAVE + RS * (XNEW - XSAVE): YE = YSAVE + RS * (YNEW - YSAVE)

3010    ZE = ZSAVE + RS * (ZNEW - ZSAVE): WE = WSAVE + RS * (WNEW - WSAVE)

3020    XNEW = XSAVE: YNEW = YSAVE: ZNEW = ZSAVE: WNEW = WSAVE

3030    LSUM = LSUM + LOG(DF): NL = NL + 1

3040    L = .721347 * LSUM / NL

3050    IF ODE% = 1 OR ODE% = 7 THEN L = L / EPS

3060    IF N > 1000 AND N MOD 10 = 0 THEN LOCATE 1, WID% - 4: PRINT USING "##.##"; L;

3070 RETURN

 

3100 REM Resize the screen

3110 IF D% = 1 THEN YMIN = XMIN: YMAX = XMAX

3120 IF XMAX - XMIN < .000001 THEN XMIN = XMIN - .0000005: XMAX = XMAX + .0000005

3130 IF YMAX - YMIN < .000001 THEN YMIN = YMIN - .0000005: YMAX = YMAX + .0000005

3140 IF ZMAX - ZMIN < .000001 THEN ZMIN = ZMIN - .0000005: ZMAX = ZMAX + .0000005

3150 IF WMAX - WMIN < .000001 THEN WMIN = WMIN - .0000005: WMAX = WMAX + .0000005

3160 MX = .1 * (XMAX - XMIN): MY = .1 * (YMAX - YMIN)

3170 XL = XMIN - MX: XH = XMAX + MX: YL = YMIN - MY: YH = YMAX + 1.5 * MY

3180 WINDOW (XL, YL)-(XH, YH): CLS

3190 YH = YH - .5 * MY

3200 XA = (XL + XH) / 2: YA = (YL + YH) / 2

3210 IF D% < 3 THEN GOTO 3310

3220    ZA = (ZMAX + ZMIN) / 2

3230    IF TRD% = 1 THEN LINE (XL, YL)-(XH, YH), COLR%(1), BF: GOSUB 5400

3240    IF TRD% = 4 THEN LINE (XL, YL)-(XH, YH), WH%, BF

3250    IF TRD% = 5 THEN LINE (XA, YL)-(XA, YH)

3260    IF TRD% <> 6 THEN GOTO 3310

3270        FOR I% = 1 TO 3

3280            XP = XL + I% * (XH - XL) / 4: LINE (XP, YL)-(XP, YH)

3290            YP = YL + I% * (YH - YL) / 4: LINE (XL, YP)-(XH, YP)

3300        NEXT I%

3310 IF PJT% <> 1 THEN LINE (XL, YL)-(XH, YH), , B

3320 IF PJT% = 1 AND TRD% < 5 THEN CIRCLE (XA, YA), .36 * (XH - XL)

3330 TT = 3.1416 / (XMAX - XMIN): PT = 3.1416 / (YMAX - YMIN)

3340 IF QM% <> 2 THEN GOTO 3400         'Not in evaluate mode

3350    LOCATE 1, 1: PRINT "<Space Bar>: Discard       <Enter>: Save";

3360    IF WID% < 80 THEN GOTO 3390

3370    LOCATE 1, 49: PRINT "<Esc>: Exit";

3380    LOCATE 1, 69: PRINT CINT((LOF(1) - 128 * LOC(1)) / 1024); "K left";

3390    GOTO 3430

3400 LOCATE 1, 1: IF LEN(CODE$) < WID% - 18 THEN PRINT CODE$

3410 IF LEN(CODE$) >= WID% - 18 THEN PRINT LEFT$(CODE$, WID% - 23) + "..."

3420 LOCATE 1, WID% - 17: PRINT "F =": LOCATE 1, WID% - 7: PRINT "L ="

3430 TIA = .05               'Tangent of illumination angle

3440 XZ = -TIA * (XMAX - XMIN) / (ZMAX - ZMIN)

3450 YZ = TIA * (YMAX - YMIN) / (ZMAX - ZMIN)

3460 RETURN

 

3500 REM Produce sound

3510 FREQ% = 220 * 2 ^ (CINT(36 * (XNEW - XL) / (XH - XL)) / 12)

3520 DUR = 1

3530 IF D% > 1 THEN DUR = 2 ^ INT(.5 * (YH - YL) / (YNEW - 9 * YL / 8 + YH / 8))

3540 SOUND FREQ%, DUR: IF PLAY(0) THEN PLAY "MF"

3550 RETURN

 

3600 REM Respond to user command

3610 IF ASC(Q$) > 96 THEN Q$ = CHR$(ASC(Q$) - 32)   'Convert to upper case

3620 IF QM% = 2 THEN GOSUB 5800                 'Process evaluation command

3630 IF INSTR("ACDEHINPRSVX", Q$) = 0 THEN GOSUB 4200   'Display menu screen

3640 IF Q$ = "A" THEN T% = 1: QM% = 0

3650 IF ODE% > 1 THEN D% = ODE% + 5

3660 IF ODE% = 1 THEN D% = D% + 2

3670 IF Q$ = "C" THEN IF N > 999 THEN N = 999

3680 IF Q$ = "D" THEN D% = 1 + (D% MOD 12): T% = 1

3690 IF D% > 6 THEN ODE% = D% - 5: D% = 4: GOTO 3710

3700 IF D% > 4 THEN ODE% = 1: D% = D% - 2 ELSE ODE% = 0

3710 IF Q$ = "E" THEN T% = 1: QM% = 2

3720 IF Q$ = "H" THEN FTH% = (FTH% + 1) MOD 3: T% = 3: IF N > 999 THEN N = 999: GOSUB 5600

3730 IF Q$ = "I" THEN IF T% <> 1 THEN SCREEN 0: WIDTH 80: COLOR 15, 1: CLS : LINE INPUT "Code? "; CODE$: IF CODE$ = "" THEN Q$ = " ": CLS :  ELSE T% = 1: QM% = 1: GOSUB 4700

3740 IF Q$ = "N" THEN NMAX = 10 * (NMAX - 1000) + 1000: IF NMAX > 10 ^ 10 THEN NMAX = 2000

3750 IF Q$ = "P" THEN PJT% = (PJT% + 1) MOD 5: T% = 3: IF N > 999 THEN N = 999

3760 IF Q$ = "R" THEN TRD% = (TRD% + 1) MOD 7: T% = 3: IF N > 999 THEN N = 999: GOSUB 5600

3770 IF Q$ = "S" THEN SND% = (SND% + 1) MOD 2: T% = 3

3780 IF Q$ = "V" THEN SAV% = (SAV% + 1) MOD 5: FAV$ = CHR$(87 + SAV% MOD 4): T% = 3: IF N > 999 THEN N = 999

3790 IF Q$ = "X" THEN T% = 0

3800 RETURN

 

3900 REM Calculate fractal dimension

3910 IF N < 1000 THEN GOTO 4010         'Wait for transient to settle

3920 IF N = 1000 THEN D2MAX = (XMAX - XMIN) ^ 2 + (YMAX - YMIN) ^ 2 + (ZMAX - ZMIN) ^ 2 + (WMAX - WMIN) ^ 2

3930 J% = (P% + 1 + INT(480 * RND)) MOD 500

3940 DX = XNEW - XS(J%): DY = YNEW - YS(J%): DZ = ZNEW - ZS(J%): DW = WNEW - WS(J%)

3950 D2 = DX * DX + DY * DY + DZ * DZ + DW * DW

3960 IF D2 < .001 * TWOD% * D2MAX THEN N2 = N2 + 1

3970 IF D2 > .00001 * TWOD% * D2MAX THEN GOTO 4010

3980    N1 = N1 + 1

3990    F = .434294 * LOG(N2 / (N1 - .5))

4000    LOCATE 1, WID% - 14: PRINT USING "##.##"; F;

4010 RETURN

 

4100 REM Project onto a sphere

4110 TH = TT * (XMAX - XP)

4120 PH = PT * (YMAX - YP)

4130 XP = XA + .36 * (XH - XL) * COS(TH) * SIN(PH)

4140 YP = YA + .5 * (YH - YL) * COS(PH)

4150 RETURN

 

4200 REM Display menu screen

4210 SCREEN 0: WIDTH 80: COLOR 15, 1: CLS

4220 WHILE Q$ = "" OR INSTR("AEIX", Q$) = 0

4230    LOCATE 1, 27: PRINT "STRANGE ATTRACTOR PROGRAM"

4240    PRINT TAB(27); "IBM PC BASIC Version 2.0"

4250    PRINT TAB(27); "(c) 1993 by J. C. Sprott"

4260    PRINT : PRINT

4270    PRINT TAB(27); "A: Search for attractors"

4280    PRINT TAB(27); "C: Clear screen and restart"

4290    IF ODE% > 1 THEN PRINT TAB(27); "D: System is 4-D special map "; CHR$(87 + ODE%); " ": GOTO 4320

4300    PRINT TAB(27); "D: System is"; STR$(D%); "-D polynomial ";

4310    IF ODE% = 1 THEN PRINT "ODE" ELSE PRINT "map"

4320    PRINT TAB(27); "E: Evaluate attractors"

4330    PRINT TAB(27); "H: Fourth dimension is ";

4340        IF FTH% = 0 THEN PRINT "projection"

4350        IF FTH% = 1 THEN PRINT "bands     "

4360        IF FTH% = 2 THEN PRINT "colors    "

4370    PRINT TAB(27); "I: Input code from keyboard"

4380    PRINT TAB(27); "N: Number of iterations is 10^";

4390    PRINT USING "#"; CINT(LOG(NMAX - 1000) / LOG(10))

4400    PRINT TAB(27); "P: Projection is ";

4410        IF PJT% = 0 THEN PRINT "planar   "

4420        IF PJT% = 1 THEN PRINT "spherical"

4430        IF PJT% = 2 THEN PRINT "horiz cyl"

4440        IF PJT% = 3 THEN PRINT "vert cyl "

4450        IF PJT% = 4 THEN PRINT "toroidal "

4460    PRINT TAB(27); "R: Third dimension is ";

4470        IF TRD% = 0 THEN PRINT "projection"

4480        IF TRD% = 1 THEN PRINT "shadow    "

4490        IF TRD% = 2 THEN PRINT "bands     "

4500        IF TRD% = 3 THEN PRINT "colors    "

4510        IF TRD% = 4 THEN PRINT "anaglyph  "

4520        IF TRD% = 5 THEN PRINT "stereogram"

4530        IF TRD% = 6 THEN PRINT "slices    "

4540    PRINT TAB(27); "S: Sound is ";

4550        IF SND% = 0 THEN PRINT "off"

4560        IF SND% = 1 THEN PRINT "on "

4570    PRINT TAB(27); "V: ";

4580        IF SAV% = 0 THEN PRINT "No data will be saved       "

4590        IF SAV% > 0 THEN PRINT FAV$; " will be saved in "; FAV$; "DATA.DAT"

4600    PRINT TAB(27); "X: Exit program"

4610    Q$ = INKEY$

4620    IF Q$ <> "" THEN GOSUB 3600     'Respond to user command

4630 WEND

4640 RETURN

 

4700 REM Get dimension and order

4710 D% = 1 + INT((ASC(LEFT$(CODE$, 1)) - 65) / 4)

4720 IF D% > 6 THEN ODE% = ASC(LEFT$(CODE$, 1)) - 87: D% = 4: GOSUB 6200: GOTO 4770

4730 IF D% > 4 THEN D% = D% - 2: ODE% = 1 ELSE ODE% = 0

4740 O% = 2 + (ASC(LEFT$(CODE$, 1)) - 65) MOD 4

4750 M% = 1: FOR I% = 1 TO D%: M% = M% * (O% + I%): NEXT I%

4760 IF D% > 2 THEN FOR I% = 3 TO D%: M% = M% / (I% - 1): NEXT I%

4770 IF LEN(CODE$) = M% + 1 OR QM% <> 1 THEN GOTO 4810

4780    BEEP        'Illegal code warning

4790    WHILE LEN(CODE$) < M% + 1: CODE$ = CODE$ + "M": WEND

4800    IF LEN(CODE$) > M% + 1 THEN CODE$ = LEFT$(CODE$, M% + 1)

4810 RETURN

 

4900 REM Save attractor to disk file SA.DIC

4910 OPEN "SA.DIC" FOR APPEND AS #1

4920 PRINT #1, CODE$; : PRINT #1, USING "##.##"; F; L

4930 CLOSE #1

4940 RETURN

 

5000 REM Plot point on screen

5010 C4% = WH%

5020 IF D% < 4 THEN GOTO 5050

5030    IF FTH% = 1 THEN IF INT(30 * (W - WMIN) / (WMAX - WMIN)) MOD 2 THEN GOTO 5330

5040    IF FTH% = 2 THEN C4% = 1 + INT(NC% * (W - WMIN) / (WMAX - WMIN) + NC%) MOD NC%

5050 IF D% < 3 THEN PSET (XP, YP): GOTO 5330    'Skip 3-D stuff

5060 IF TRD% = 0 THEN PSET (XP, YP), C4%

5070 IF TRD% <> 1 THEN GOTO 5130

5080    IF D% > 3 AND FTH% = 2 THEN PSET (XP, YP), C4%: GOTO 5110

5090    C% = POINT(XP, YP)

5100    IF C% = COLR%(2) THEN PSET (XP, YP), COLR%(3) ELSE IF C% <> COLR%(3) THEN PSET (XP, YP), COLR%(2)

5110    XP = XP - XZ * (Z - ZMIN): YP = YP - YZ * (Z - ZMIN)

5120    IF POINT(XP, YP) = COLR%(1) THEN PSET (XP, YP), 0

5130 IF TRD% <> 2 THEN GOTO 5160

5140    IF D% > 3 AND FTH% = 2 AND (INT(15 * (Z - ZMIN) / (ZMAX - ZMIN) + 2) MOD 2) = 1 THEN PSET (XP, YP), C4%

5150    IF D% < 4 OR FTH% <> 2 THEN C% = COLR%(INT(60 * (Z - ZMIN) / (ZMAX - ZMIN) + 4) MOD 4): PSET (XP, YP), C%

5160 IF TRD% = 3 THEN PSET (XP, YP), COLR%(INT(NC% * (Z - ZMIN) / (ZMAX - ZMIN) + NC%) MOD NC%)

5170 IF TRD% <> 4 THEN GOTO 5240

5180    XRT = XP + XZ * (Z - ZA): C% = POINT(XRT, YP)

5190    IF C% = WH% THEN PSET (XRT, YP), RD%

5200    IF C% = CY% THEN PSET (XRT, YP), BK%

5210    XLT = XP - XZ * (Z - ZA): C% = POINT(XLT, YP)

5220    IF C% = WH% THEN PSET (XLT, YP), CY%

5230    IF C% = RD% THEN PSET (XLT, YP), BK%

5240 IF TRD% <> 5 THEN GOTO 5280

5250    HSF = 2                 'Horizontal scale factor

5260    XRT = XA + (XP + XZ * (Z - ZA) - XL) / HSF: PSET (XRT, YP), C4%

5270    XLT = XA + (XP - XZ * (Z - ZA) - XH) / HSF: PSET (XLT, YP), C4%

5280 IF TRD% <> 6 THEN GOTO 5330

5290    DZ = (15 * (Z - ZMIN) / (ZMAX - ZMIN) + .5) / 16

5300    XP = (XP - XL + (INT(16 * DZ) MOD 4) * (XH - XL)) / 4 + XL

5310    YP = (YP - YL + (3 - INT(4 * DZ) MOD 4) * (YH - YL)) / 4 + YL

5320    PSET (XP, YP), C4%

5330 RETURN

 

5400 REM Plot background grid

5410 FOR I% = 0 TO 15           'Draw 15 vertical grid lines

5420    XP = XMIN + I% * (XMAX - XMIN) / 15

5430    LINE (XP, YMIN)-(XP, YMAX), 0

5440 NEXT I%

5450 FOR I% = 0 TO 10           'Draw 10 horizontal grid lines

5460    YP = YMIN + I% * (YMAX - YMIN) / 10

5470    LINE (XMIN, YP)-(XMAX, YP), 0

5480 NEXT I%

5490 RETURN

 

5600 REM Set colors

5610 NC% = 15                   'Number of colors

5620 COLR%(0) = 0: COLR%(1) = 8: COLR%(2) = 7: COLR%(3) = 15

5630 IF TRD% = 3 OR (D% > 3 AND FTH% = 2 AND TRD% <> 1) THEN FOR I% = 0 TO NC%: COLR%(I%) = I% + 1: NEXT I%

5640 WH% = 15: BK% = 8: RD% = 12: CY% = 11

5650 IF SM% > 2 THEN GOTO 5720  'Not in CGA mode

5660    WID% = 80: IF D% < 3 THEN SCREEN 2: GOTO 5720

5670    IF (TRD% = 0 OR TRD% > 4) AND (D% = 3 OR FTH% <> 2) THEN SCREEN 2: GOTO 5720

5680    WID% = 40: SCREEN 1

5690    COLR%(0) = 0: COLR%(1) = 2: COLR%(2) = 1: COLR%(3) = 3

5700    WH% = 3: BK% = 0: RD% = 2: CY% = 1

5710    FOR I% = 4 TO NC%: COLR%(I%) = COLR%(I% MOD 4 + 1): NEXT I%

5720 RETURN

 

5800 REM Process evaluation command

5810 IF Q$ = " " THEN T% = 2: NE = NE + 1: CLS

5820 IF Q$ = CHR$(13) THEN T% = 2: NE = NE + 1: CLS : GOSUB 5900

5830 IF Q$ = CHR$(27) THEN CLS : GOSUB 6000: Q$ = " ": QM% = 0: GOTO 5850

5840 IF Q$ <> CHR$(27) AND INSTR("CHNPRVS", Q$) = 0 THEN Q$ = ""

5850 RETURN

 

5900 REM Save favorite attractors to disk file FAVORITE.DIC

5910 OPEN "FAVORITE.DIC" FOR APPEND AS #2

5920 PRINT #2, CODE$

5930 CLOSE #2

5940 RETURN

 

6000 REM Update SA.DIC file

6010 LOCATE 11, 9: PRINT "Evaluation complete"

6020 LOCATE 12, 8: PRINT NE; "cases evaluated"

6030 OPEN "SATEMP.DIC" FOR OUTPUT AS #2

6040 IF QM% = 2 THEN PRINT #2, CODE$

6050 WHILE NOT EOF(1): LINE INPUT #1, CODE$: PRINT #2, CODE$: WEND

6060 CLOSE

6070 KILL "SA.DIC"

6080 NAME "SATEMP.DIC" AS "SA.DIC"

6090 RETURN

 

6200 REM Special function definitions

6210 ZNEW = X * X + Y * Y       'Default 3rd and 4th dimension

6220 WNEW = (N - 100) / 900: IF N > 1000 THEN WNEW = (N - 1000) / (NMAX - 1000)

6230 IF ODE% <> 2 THEN GOTO 6270

6240    M% = 10

6250    XNEW = A(1) + A(2) * X + A(3) * Y + A(4) * ABS(X) + A(5) * ABS(Y)

6260    YNEW = A(6) + A(7) * X + A(8) * Y + A(9) * ABS(X) + A(10) * ABS(Y)

6270 IF ODE% <> 3 THEN GOTO 6310

6280    M% = 14

6290    XNEW = A(1) + A(2) * X + A(3) * Y + (CINT(A(4) * X) AND CINT(A(5) * Y)) + (CINT(A(6) * X) OR CINT(A(7) * Y))

6300    YNEW = A(8) + A(9) * X + A(10) * Y + (CINT(A(11) * X) AND CINT(A(12) * Y)) + (CINT(A(13) * X) OR CINT(A(14) * Y))

6310 IF ODE% <> 4 THEN GOTO 6350

6320    M% = 14

6330    XNEW = A(1) + A(2) * X + A(3) * Y + A(4) * ABS(X) ^ A(5) + A(6) * ABS(Y) ^ A(7)

6340    YNEW = A(8) + A(9) * X + A(10) * Y + A(11) * ABS(X) ^ A(12) + A(13) * ABS(Y) ^ A(14)

6350 IF ODE% <> 5 THEN GOTO 6390

6360    M% = 18

6370    XNEW = A(1) + A(2) * X + A(3) * Y + A(4) * SIN(A(5) * X + A(6)) + A(7) * SIN(A(8) * Y + A(9))

6380    YNEW = A(10) + A(11) * X + A(12) * Y + A(13) * SIN(A(14) * X + A(15)) + A(16) * SIN(A(17) * Y + A(18))

6390 IF ODE% <> 6 THEN GOTO 6450

6400    M% = 6

6410    IF N < 2 THEN AL = TWOPI / (13 + 10 * A(6)): SINAL = SIN(AL): COSAL = COS(AL)

6420    DUM = X + A(2) * SIN(A(3) * Y + A(4))

6430    XNEW = 10 * A(1) + DUM * COSAL + Y * SINAL

6440    YNEW = 10 * A(5) - DUM * SINAL + Y * COSAL

6450 IF ODE% <> 7 THEN GOTO 6500

6460    M% = 9

6470    XNEW = X + EPS * A(1) * Y

6480    YNEW = Y + EPS * (A(2) * X + A(3) * X * X * X + A(4) * X * X * Y + A(5) * X * Y * Y + A(6) * Y + A(7) * Y * Y * Y + A(8) * SIN(Z))

6490    ZNEW = Z + EPS * (A(9) + 1.3): IF ZNEW > TWOPI THEN ZNEW = ZNEW - TWOPI

6500 RETURN

 

6600 REM Find legal graphics mode

6610 SM% = SM% - 1

6620 IF SM% = 0 THEN PRINT "This program requires a graphics monitor": STOP

6630 RESUME

 

6700 REM Project onto a horizontal cylinder

6710 PH = PT * (YMAX - YP)

6720 YP = YA + .5 * (YH - YL) * COS(PH)

6730 RETURN

 

6800 REM Project onto a vertical cylinder

6810 TH = TT * (XMAX - XP)

6820 XP = XA + .5 * (XH - XL) * COS(TH)

6830 RETURN

 

6900 REM Project onto a torus (unity aspect ratio)

6910 TH = TT * (XMAX - XP)

6920 PH = 2 * PT * (YMAX - YP)

6930 XP = XA + .18 * (XH - XL) * (1 + COS(TH)) * SIN(PH)

6940 YP = YA + .25 * (YH - YL) * (1 + COS(TH)) * COS(PH)

6950 RETURN

 

7000 REM Save data

7010 IF N = 1001 THEN CLOSE #3: OPEN FAV$ + "DATA.DAT" FOR OUTPUT AS #3

7020 IF SAV% = 1 THEN DUM = XNEW

7030 IF SAV% = 2 THEN DUM = YNEW

7040 IF SAV% = 3 THEN DUM = ZNEW

7050 IF SAV% = 4 THEN DUM = WNEW

7060 PRINT #3, CSNG(DUM)

7070 RETURN

 

Phew! That was fun!