08

Fans, Bars and Noise

This is the second half of ALL.PAS. These are all still pure palette cycling, with no pixels drawn after initial setup, but wandering outside the circle theme.
the 256 DAC registers. Every pattern here animates this and nothing else.

P10

Two overlapping fans, one anchored on the top and bottom edges, one on the left and right. The color index is a triangle wave of period 120, so each index recurs at three or four separate places in the fan, which is what turns a moving palette band into several moving bands at once. Two chasers here; P15 is this exact drawing with four. P12 is a third fan through the same center but drawn from two separate loops over a wider span, so it is a cousin rather than a twin.

P11

draw_line(x,0,x,480,x) for x=0..359, but the color parameter is taken as a byte, so columns 256..359 repeat indices 0..103. The seam is at x=256, and the blue ramp scrolls through it. This is WIGGLE six months early, without the triangle table.

P12

Another centered fan but drawn differently from P10/P15. Note that the version saved in the archive had a bug that breaks the effect; uncheck the "index the ramp" toggle to see the buggy version. I absolutely remember the fixed version running back then, so this seems like a work in progress issue that snuck into the archive.

P13

The random(abs(180-x)+abs(240-c)+5) makes the RANGE of the noise grow with Manhattan distance from center, so the middle stays dark and calm and the corners go wild. Mirrored into four quadrants. The argument can reach 425, past a byte, so the far corners wrap through the palette and band.

P14

A fan radiating from (180,1) down to the bottom edge. The palette starts black, but only for an instant: p and s are BYTES, so 50+p and 150+s run past their banks and wrap at 255, scribbling values across all 256 registers. All four writes land in the visible 50..110 range, at four different phases and two different rates (p steps 1, period 256; s steps 2, period 128). Four sweeps beating against each other in time, over a triangle-wave index that repeats in space, give the moiré effect. The values written wrap too: 3+p exceeds 63 and 60-p goes negative, so the gradients themselves are sawtooths. Back then, I think I was mostly excited about the weird patterns that emerged from code that is only drawing straight lines.

P15

P10's geometry with P14's four chasers instead of two, and both banks pre-filled rather than black. Twice the interference sources over a picture whose line density climbs steeply toward the center, so the pattern is finest exactly where the eye goes. But back then, I was probably just thinking it looked cool.

ALL.PAS

1996-08-08 05:19 · 6,490 bytes · Fifteen patterns, all enabled.

Uses Crt,jmodex;Var X:Integer;a:char;

Procedure i;begin IF SET_VGA_MODEX(7,360,480,1)=0 THEN halt(0);
CLEAR_VGA_SCREEN(0);end;

Procedure circ(x,y,r,l:integer);var b,c:integer;a:real;begin if r=0then b:=0
else b:=round(sqrt(r*r-1));a:=b;for c:=0to round(r/sqrt(2))do begin if a=0then
a:=1;a:=(a-(c/a));b:=round(a);draw_line(x+b,y+c,x-b,y+c,l);draw_line(x+b,y-c,
x-b,y-c,l);draw_line(x+c,y+b,x-c,y+b,l);draw_line(x+c,y-b,x-c,y-b,l);end;end;

Procedure P0;Var s:string;Begin i;s:=
'Circle Demos: Press any key for next pattern';set_dac_register(255,50,50,50);
TPrint_Str(s,45,-5,460,255);s:='Please wait... Initializing';TPrint_Str(s,28,
70,0,255);End;
Procedure P1;var r,s,t:integer;begin for x:=1to 254do set_dac_register(x,0,
0,0);for x:=1to 180do circ(180,240,180-x,x-1);fill_block(70,0,292,7,0);
s:=0;t:=0;r:=1;repeat repeat
until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;for x:=1to 180do
set_dac_register(x,(x+s)*r,x+t,x+t);s:=s+r;inc(t);if(s=63)or(s=0)then r:=-r;
until keypressed;a:=readkey;end;
Procedure P2;var s,t,u:integer;d:array[1..180]of record r,g,b:byte;end;begin
for x:=1to 180do begin d[x].r:=0;d[x].g:=0;d[x].b:=0;end;s:=1;t:=1;u:=1;repeat
repeat until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;for x:=1to
180do set_dac_register(x,d[x].r,d[x].g,d[x].b);for x:=1to 179do d[x]:=d[x+1];
with d[180]do begin r:=d[179].r+s;g:=d[179].g+t;b:=d[179].b+u;if(r>(63-abs(s))
)or(r<abs(s))then s:=-s;if(g>(63-abs(t)))or(g<abs(t))then t:=-t;if(b>(63-abs
(u)))or(b<abs(u))then u:=-u;end;until keypressed;a:=readkey;end;
Procedure P3;var s,t,u:integer;d:array[0..179]of record r,g,b:byte;end;begin
for x:=0to 179do begin d[x].r:=0;d[x].g:=0;d[x].b:=0;
end;repeat repeat until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;
for x:=0to 179do set_dac_register(x+1,d[x].r,d[x].g,d[x].b);for x:=0to 178do
d[x]:=d[x+1];d[179].r:=random(63);d[179].g:=random(63);d[179].b:=random(63);
until keypressed;a:=readkey;end;
Procedure P4;var s,t,u:integer;d:array[1..180]of record r,g,b:byte;end;
begin for x:=1to 180do begin d[x].r:=0;d[x].g:=0;
d[x].b:=0;end;s:=1;t:=1;u:=1;repeat repeat until(port[$3da]and 8)=0;repeat
until(port[$3da]and 8)<>0;for x:=1to 180do set_dac_register(x,d[x].r,d[x].g,
d[x].b);for x:=1to 179do d[x]:=d[x+1];with d[180]do begin r:=d[179].r+s;g:=
d[179].g+t;b:=d[179].b+u;if(r>(64-s))or(r<s)then s:=-s;if(g>(64-t))or(g<t)then
t:=-t;if(b>(64-u))or(b<u)then u:=-u;end;until keypressed;a:=readkey;end;
Procedure P5;var q,r,g,b,s,t,u:integer;begin s:=34;t:=11;u:=10;r:=1;g:=1;b:=1;
repeat repeat until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;for
q:=1to 180do begin set_dac_register(q,s,t,u);s:=s+r;t:=t+g;u:=u+b;if(s=63)or(s
=0)then r:=-r;if(t=63)or(t=0)then g:=-g;if(u=63)or(u=0)then b:=-b;end;until
keypressed;a:=readkey;end;
Procedure P6;var q:byte;e:array[1..180]of record r,g,b:byte;end;s,t,u:record
m,d:shortint;end;begin s.m:=1;t.m:=1;u.m:=1;s.d:=1;t.d:=1;u.d:=1;repeat repeat
until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;for q:=1to 180do
set_dac_register(q,e[q].r,e[q].g,e[q].b);for q:=1to 179do e[q]:=e[q+1];with
e[180]do begin if((s.d>0)and(r>=(63-s.m)))or((s.d<0)and(r<=s.m))then s.d:=-s.d
;if((t.d>0)and(g>=(63-t.m)))or((t.d<0)and(g<=t.m))then t.d:=-t.d;if((u.d>0)and
(b>=(63-u.m)))or((u.d<0)and(b<=u.m))then u.d:=-u.d;r:=e[179].r+(s.m*s.d);g:=
e[179].g+(t.m*t.d);b:=e[179].b+(u.m*u.d);s.m:=random(2)+1;t.m:=random(2)+1;
u.m:=random(2)+1;end;until keypressed;a:=readkey;end;
Procedure P7;var r,g,b,s,t,u:integer;begin for x:=1to 254do set_dac_register
(x,0,0,0);for x:=0to 63do circ(180,240,63-x,x);s:=34;t:=11;u:=0;r:=1;g:=1;
b:=1;repeat repeat until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;
for x:=1to 64do set_dac_register(x,x+s,x+t,x+u);s:=s+r;t:=t+g;u:=u+b;if(s=63)
or(s=0)then r:=-r;if(t=63)or(t=0)then g:=-g;if(u=63)or(u=0)then b:=-b;until
keypressed;a:=readkey;end;

Procedure P10;var c,dc:integer;s,p:byte;Begin i;c:=0;dc:=1;FOR X:=0TO 60DO
SET_DAC_REGISTER(50+X,x,0,60-X);for x:=0to 360do begin DRAW_LINE(x,1,360-x,
479,c+50);draw_line(1,x+60,360,420-x,c+50);c:=c+DC;IF(c=0)OR(c=60)THEN DC:=
-DC;end;p:=3;s:=0;repeat Set_Dac_Register(50+P,3+P,0,60-P);Set_Dac_Register
(50+S,S,10,63-S);p:=p+1;s:=s+2;until keypressed;a:=readkey;END;

Procedure P11;Var S:Byte;Begin i;FOR x:=1TO 255DO Begin SET_DAC_REGISTER
(x,0,0,x div 4);end;for x:=0to 359do draw_line(x,0,x,480,x);repeat repeat
until(port[$3da]and 8)=0;repeat until(port[$3da]and 8)<>0;for x:=1to 359do
Set_Dac_Register(x,0,0,(s+x)div 4);s:=s+3;until keypressed;a:=readkey;END;

Procedure P12;Var c,dc,s:Integer;Begin i;c:=0;dc:=1;for x:=0to 60do
set_dac_register(50+x,x,0,60-x);for x:=0to 360do begin draw_line(x,0,360-x,
480,c+50);c:=c+dc;if(c=0)or(c=60)then dc:=-dc;end;for x:=0to 480do begin
draw_line(0,x,360,480-x,c+50);c:=c+dc;if(c=0)or(c=60)then dc:=-dc;end;s:=0;
repeat for x:=0to 60do Set_Dac_Register(50+x,s,0,s);s:=s+3;until keypressed;
a:=readkey;end;

Procedure P13;Var c,s:Integer;Begin i;for x:=1to 255do Begin set_dac_register
(X,x div 4,0,x div 4);end;for x:=0to 180do for c:=0to 240do begin s:=random
(abs(180-x)+abs(240-c)+5);set_point(x,c,s);set_point(360-x,c,s);set_point(x,
480-c,s);set_point(360-x,480-c,s);end;repeat for x:=1to 255do Set_Dac_Register
(x,s+x,0,s+x);s:=s+3;delay(10);until keypressed;a:=readkey;end;

Procedure P14;Var c,dc:Integer;s,p:Byte;Begin i;c:=0;dc:=1;for x:=0to 60do
Begin set_dac_register(50+x,0,0,0);set_dac_register(150+x,0,0,0);end;for x:=0
to 180do begin draw_line(180,1,x,479,c+50);draw_line(180,1,359-x,479,c+50);c:=
c+dc;if(c=0)or(c=60)then dc:=-dc;end;p:=3;s:=0;repeat Set_Dac_Register(50+p,
3+p,0,60-p);Set_Dac_Register(50+s,s,10,63-s);Set_Dac_Register(150+p,3+p,0,
60-p);Set_Dac_Register(150+s,63,63,s);inc(p);inc(s,2);until keypressed;
a:=readkey;end;

Procedure P15;Var c,dc:Integer;s,p:Byte;Begin i;c:=0;dc:=1;for x:=0to 60do
Begin set_dac_register(50+x,x,0,60-x);set_dac_register(150+x,x,0,60-x);end;for
x:=0to 360do begin draw_line(x,1,360-x,479,c+50);draw_line(1,x+60,360,420-x,
c+50);c:=c+dc;if(c=0)or(c=60)then dc:=-dc;end;p:=3;s:=0;repeat
Set_Dac_Register(50+p,3+p,0,60-p);Set_Dac_Register(50+s,s,10,63-s);
Set_Dac_Register(150+p,3+p,0,60-p);Set_Dac_Register(150+s,63,63,s);inc(p);inc
(s,2);until keypressed;a:=readkey;end;


Procedure CircleDemos;Begin P1;P2;P3;P4;P5;P6;P7;end;

Begin P0;CircleDemos;P10;P11;P12;P13;P14;P15;

asm mov ah,0;mov al,3;int 16;end;END.