Date   : Wed, 08 Mar 2006 11:34:07 -0000
From   : "David Hunt" <dm.hunt@...>
Subject: Re: Warning: Sad case on list!

> > Heh. Use 16 of them to do the fractal calculations, with the beebs on
> > RS-nnn to front the graphics. ;-b'
> 
> I think that's a great idea, get the mainframes/minis talking to the Beebs
> over serial sending VDU commands. Then all you need to do is get the Beebs
> into serial input mode and you're away.
> 
> You could have banks of Beebs driven by different mainframe/mini
> computers.
> If you drew blocks on each Beeb at 1280x1024 (160x256 Mode 2) and then
> tunnelled down, so you then have four blocks of 640x512 and then sixteen
> blocks of 320x256 etc. so you see a Mandelbrot set gradually "come into
> focus" The mainframe/mini would either calculate and cache so the "focus"
> would be linear, or draw the blocks as they are calculated. Depends on how
> fast the mainframe/mini is. People want to see an image built up but
> conversely don't want to wait more than 5-10 minutes.
> 
>    10 MODE2:VDU23;8202;0;0;0;
>    20 *FX9
>    30 AR=-2:AI=-1.25:S=2.5:D=S/1280
>    40 FORE%=1024TO128STEP-128
>    50   C%=E%DIV32:D%=E%DIV16
>    60   FORY%=0TO1024STEPC%
>    70     FORX%=0TO1280STEPD%
>    80       CR=X%*D+AR:CI=Y%*D+AI:ZR=CR:ZI=CI:I%=0
>    90       REPEAT
>   100         A=ZR^2:B=ZI^2:L=SQR(A+B):ZI=2*ZR*ZI+CI:ZR=A-B+CR:I%=I%+1
>   110       UNTIL L>2 OR I%>15
>   120       GCOL0,I%
>   130
> IFC%=4THENPLOT69,X%,Y%ELSEMOVEX%,Y%:MOVEX%+D%,Y%:PLOT85,X%,Y%+C%:MOVEX%+D%
> ,Y
> %:MOVEX%+D%,Y%+C%:PLOT85,X%,Y%+C%
>   140     NEXT
>   150   NEXT
>   160 NEXT
> 
> Just knocked this up to show you what I mean. Runs in less than a second
> on
> BBC Basic for Windows... Will take eons on a real Beeb, a lot less time on
> an Arc or something with a bit more poke than a Beeb.
> 
> Dave ;)

   10 MODE2:VDU23;8202;0;0;0;
   20 *FX9
   30 AR=-2:AI=-1.25:S=2.5:D=S/1280:TIME=0
   40 E%=512
   50 REPEAT
   60   C%=E%*4:D%=E%*8
   70   FORY%=0TO1024STEPC%
   80     FORX%=0TO1280STEPD%
   90       CR=X%*D+AR:CI=Y%*D+AI:ZR=CR:ZI=CI:I%=0
  100       REPEAT
  110         A=ZR^2:B=ZI^2:L=SQR(A+B):ZI=2*ZR*ZI+CI:ZR=A-B+CR:I%=I%+1
  120       UNTIL L>2 OR I%>15
  130       GCOL0,I%
  140
IFC%=4THENPLOT69,X%,Y%ELSEMOVEX%,Y%:MOVEX%+D%,Y%:PLOT85,X%,Y%+C%:MOVEX%+D%,Y
%:MOVEX%+D%,Y%+C%:PLOT85,X%,Y%+C%
  150     NEXT
  160   NEXT
  170   E%=E%DIV2
  180 UNTIL C%=4
  190 T%=TIME
  200 *SAVE"IMG"FFFF3000+5000
  210 END

This listing gives a couple more features, plus an proper focussing divisor.

Dave ;)