ZXASCII
AUTO -1
PROG demos:graphics/elastic
CHANGED FALSE
10 REM Elastic grid
20 LET cellsizea=20: LET cellsizeb=20: LET grida=SCRw/cellsizea: LET gridb=SCRh/cellsizeb: LET nodesize=4: LET relax=0.99: LET fade=0.99: LET vel=7: LET dist=800: SCREEN LOCK: INK 15
30 PALETTE 1,128,128,128: FOR f=2 TO 255: LET i=128+(f/2): PALETTE f,128,i,i: NEXT f
40 OPTION "base",0
50 DIM origa(): DIM origb(): DIM worka(): DIM workb(): DIM dir1(): DIM vel1(): DIM dir2(): DIM vel2()
60 FOR a=1 TO grida-1: FOR b=1 TO gridb-1: LET origa(a,b)=cellsizea*a: LET origb(a,b)=cellsizeb*b: LET worka(a,b)=cellsizea*a: LET workb(a,b)=cellsizeb*b: LET dir1(a,b)=0: LET vel1(a,b)=0: LET dir2(a,b)=0: LET vel2(a,b)=0: NEXT b: NEXT a
70 LET oldmousex=MOUSEx: LET oldmousey=MOUSEy
80 GO SUB 160
90 CLS 0: LET oldmousex=newMOUSEx: LET oldmousey=newMOUSEy
100 INK 8: FOR a=1 TO grida-2: FOR b=1 TO gridb-2: DRAW worka(a,b),workb(a,b) TO worka(a+1,b),workb(a+1,b): DRAW worka(a,b),workb(a,b) TO worka(a,b+1),workb(a,b+1): NEXT b: NEXT a
110 FOR a=1 TO grida-2: DRAW worka(a,b),workb(a,b) TO worka(a+1,b),workb(a+1,b): NEXT a
120 FOR b=1 TO gridb-2: DRAW worka(a,b),workb(a,b) TO worka(a,b+1),workb(a,b+1): NEXT b
130 FOR a=1 TO grida-1: FOR b=1 TO gridb-1: INK (253/vel)*vel1(a,b)+2: CIRCLE worka(a,b),workb(a,b),4 FILL ""
140 NEXT b: NEXT a
150 WAIT SCREEN: GO TO 80
160 FOR a=1 TO grida-1: FOR b=1 TO gridb-1
170 LET newmousex=MOUSEx: LET newmousey=MOUSEy
180 IF MOUSEBTN=1 THEN 
    LET xb=newmousey-workb(a,b): 
    LET ya=newmousex-worka(a,b): 
    IF xb<>0 THEN 
       LET dir1(a,b)=2*ATN((SQR(POWERTWO ya+POWERTWO xb)-ya)/xb): 
       LET vel1(a,b)=MIN(dist/SQR abs((oldmousey-workb(a,b))^2+(oldmousex-worka(a,b))^2),vel): 
    ELSE 
       LET dir2(a,b)=0
190 LET xb=origb(a,b)-workb(a,b): LET ya=origa(a,b)-worka(a,b)
200 IF xb<>0 THEN LET dir2(a,b)=2*ATN((SQR(POWERTWO ya+POWERTWO xb)-ya)/xb): LET vel2(a,b)=SQR abs((origb(a,b)-workb(a,b))^2+(origa(a,b)-worka(a,b))^2)*.08 ELSE LET dir2(a,b)=0
210 IF MOUSEBTN=1 THEN INC worka(a,b),vel1(a,b)*COS(dir1(a,b))+vel2(a,b)*COS(dir2(a,b)): INC workb(a,b),vel1(a,b)*SIN(dir1(a,b))+vel2(a,b)*SIN(dir2(a,b)) ELSE INC worka(a,b),vel2(a,b)*COS(dir2(a,b))*relax: INC workb(a,b),vel2(a,b)*SIN(dir2(a,b))*relax
220 NEXT b: NEXT a: RETURN