flow.bas

100 ' Flow
110 ' Gilbert Francois Duivesteijn
120 '
200 COLOR 15,1,1: CLS
210 ' setup perlin noise
220 NX=2: NY=8
230 OX=0: OY=0
231 NP=20: ' nr of particles
232 ST=5.3: ' step size
233 NC=3: ' nr of colors
234 NS=29: ' nr of steps
238 ' setup noise
239 GOSUB 16000
240 ' setup fast sin/cos
250 GOSUB 18000
260 ' setup particles
270 DIM PA(NP,2)
271 ' setup palette
272 DIM CO(NC)
273 CO(0)=4
274 CO(1)=5
275 CO(2)=7
276 CO(3)=14
280 ' init particles
281 FOR I=0 TO NP
290 GOSUB 1600
310 NEXT I
315 SCREEN 2
316 FC=0
320 ' update
330 FOR I=0 TO NP
331 IF PA(I,0)<1 OR PA(I,0)>254 GOTO 332 ELSE 335
332 GOSUB 1600
335 IF PA(I,1)<1 OR PA(I,1)>191 GOTO 336 ELSE 340
336 GOSUB 1600
340 X=PA(I,0)
350 Y=PA(I,1)
360 GOSUB 16600
370 TH=4*180*Z+180
371 IF TH<0 THEN TH=TH+360
380 PA(I,0)=PA(I,0)+ST*FN FC(TH)
390 PA(I,1)=PA(I,1)+ST*FN FS(TH)
391 CP=POINT(PA(I,0),PA(I,1)): ' prev color
392 CN=CO(INT(FC/NS*(NC))): 'new color
393 IF CN>CP GOTO 400 ELSE 410
400 PSET(PA(I,0),PA(I,1)),CN
410 NEXT I
411 FC=FC+1
412 IF FC>NS GOTO 414 ELSE 420
414 FOR I=0 TO NP
415 GOSUB 1600
416 NEXT I
417 FC=0
420 GOTO 320
1600 '
1610 ' init particle
1620 ' in: PA, I
1630 '
1640 PA(I,0)=INT(RND(1)*255)
1650 PA(I,1)=INT(RND(1)*191)
1660 RETURN
16000 ' libnoise
16010 ' Perlin noise generator
16020 ' Gilbert Francois Duivesteijn
16030 '
16040 ' init: 16000
16050 ' run: 16600
16060 '
16070 ' Init Perlin noise
16080 ' in: NX,NY: nr of cells
16090 '     OX,OY: offset in pxls
16100 ' out: GX,GY: grad in nodes
16110 '      PX,PY: pxls per cell
16120 '
16130 PRINT "[i] Generating random gradient."
16140 T0=TIME
16150 PX=(256-2*OX)/NX
16160 PY=(192-2*OY)/NY
16170 PRINT "[i] px: " + STR$(PX)
16180 PRINT "[i] py: " + STR$(PY)
16190 DIM GX(NX,NY): ' grad dv/dx
16200 DIM GY(NX,NY): ' grad dv/dy
16210 FOR I=0 TO NX
16220 FOR J=0 TO NY
16230 GX(I,J) = 2*RND(TIME)-1
16240 GY(I,J) = 2*RND(TIME)-1
16250 NEXT J
16260 NEXT I
16270 T1=TIME
16280 PRINT "    Done, " + STR$((T1-T0)/50) + " sec."
16290 RETURN
16300 '
16310 ' Dot gradient
16320 ' in:  x,ix,y,iy,gx,gy
16330 ' out: dg
16340 '
16350 DX=XP-IX
16360 DY=YP-IY
16370 DG=GX(IX,IY)*DX + GY(IX,IY)*DY
16380 RETURN
16390 '
16400 ' Interpolate
16410 ' in:  n0,n1,w
16420 ' out: n2
16430 '
16440 A2=(A1-A0)*W+A0
16450 RETURN
16600 '
16610 ' Perlin noise
16620 ' in: X, Y
16630 ' out: Z
16640 '
16650 XP=(X-OX)/PX
16660 YP=(Y-OY)/PY
16670 IX=INT(XP)
16680 IY=INT(YP)
16690 GOSUB 16300
16700 Z0=DG: DG=0
16710 IX=INT(XP)+1
16720 IY=INT(YP)
16730 GOSUB 16300
16740 Z1=DG: DG=0
16750 ' point(ix0,iy1)
16760 IX=INT(XP)
16770 IY=INT(YP)+1
16780 GOSUB 16300
16790 Z2=DG: DG=0
16800 ' point(ix1,iy1)
16810 IX=INT(XP)+1
16820 IY=INT(YP)+1
16830 GOSUB 16300
16840 Z3=DG: DG=0
16850 ' interpolate
16860 A0=Z0: A1=Z1: W=XP-INT(XP)
16870 GOSUB 16390
16880 Z4=A2: A2=0
16890 A0=Z2: A1=Z3: W=XP-INT(XP)
16900 GOSUB 16390
16910 Z5=A2: A2=0
16920 A0=Z4: A1=Z5: W=YP-INT(YP)
16930 GOSUB 16390
16940 Z=A2: A2=0
16950 RETURN
18000 ' libsin
18010 ' Library for fast goniometric
18020 ' functions.
18030 ' Gilbert Francois Duivesteijn
18040 '
18050 ' init: 18000
18060 ' run: fn fs(x)
18070 ' run: fn fc(x)
18080 PI=ATN(1)*4
18090 DIM TS(360): ' table sin
18100 PRINT "[i] Building lookup table..."
18110 ' Fast sin(x) function
18120 DEF FN FS(X)=TS((X+.5) MOD 360)
18130 ' Fast cos(x) function
18140 DEF FN FC(X)=TS((X+90.5) MOD 360)
18150 ' Create lookup table
18160 ' out: ts, fn fs, fn fc, pi
18170 FOR I=0 TO 359
18180 READ TS(I)
18190 NEXT I
18200 RETURN
18210 END
18220 DATA 0.000000000000000, 0.017452406437284
18230 DATA 0.034899496702501, 0.052335956242944
18240 DATA 0.069756473744125, 0.087155742747658
18250 DATA 0.104528463267653, 0.121869343405147
18260 DATA 0.139173100960065, 0.156434465040231
18270 DATA 0.173648177666930, 0.190808995376545
18280 DATA 0.207911690817759, 0.224951054343865
18290 DATA 0.241921895599668, 0.258819045102521
18300 DATA 0.275637355816999, 0.292371704722737
18310 DATA 0.309016994374947, 0.325568154457157
18320 DATA 0.342020143325669, 0.358367949545300
18330 DATA 0.374606593415912, 0.390731128489274
18340 DATA 0.406736643075800, 0.422618261740699
18350 DATA 0.438371146789077, 0.453990499739547
18360 DATA 0.469471562785891, 0.484809620246337
18370 DATA 0.500000000000000, 0.515038074910054
18380 DATA 0.529919264233205, 0.544639035015027
18390 DATA 0.559192903470747, 0.573576436351046
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18410 DATA 0.615661475325658, 0.629320391049837
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18850 DATA 0.809016994374947, 0.798635510047293
18860 DATA 0.788010753606722, 0.777145961456971
18870 DATA 0.766044443118978, 0.754709580222772
18880 DATA 0.743144825477394, 0.731353701619171
18890 DATA 0.719339800338651, 0.707106781186548
18900 DATA 0.694658370458997, 0.681998360062498
18910 DATA 0.669130606358858, 0.656059028990507
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18940 DATA 0.587785252292473, 0.573576436351046
18950 DATA 0.559192903470747, 0.544639035015027
18960 DATA 0.529919264233205, 0.515038074910054
18970 DATA 0.500000000000000, 0.484809620246337
18980 DATA 0.469471562785891, 0.453990499739547
18990 DATA 0.438371146789077, 0.422618261740699
19000 DATA 0.406736643075800, 0.390731128489274
19010 DATA 0.374606593415912, 0.358367949545300
19020 DATA 0.342020143325669, 0.325568154457157
19030 DATA 0.309016994374948, 0.292371704722737
19040 DATA 0.275637355816999, 0.258819045102521
19050 DATA 0.241921895599668, 0.224951054343865
19060 DATA 0.207911690817759, 0.190808995376545
19070 DATA 0.173648177666930, 0.156434465040231
19080 DATA 0.139173100960065, 0.121869343405148
19090 DATA 0.104528463267654, 0.087155742747658
19100 DATA 0.069756473744126, 0.052335956242944
19110 DATA 0.034899496702501, 0.017452406437283
19120 DATA 0.000000000000000, -0.017452406437284
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