Random adventures in vic20 charcell graphics

jbevren · Post by **jbevren** » Thu Apr 28, 2011 3:26 pm

I thought I'd share a quick basic scratchup that plots a gingerbread fractal on unexpanded vic.

The program uses dynamic character cell allocation, starting from 255 and going down (potentially to 0). For informational ability, the first 64 chars are copied from ram during init.

http://jbevren.net/gingerbread-vic.zip

Beware, it plots some 10k points in two phases, so it takes 20-30 minutes.

Feel free to modify the start points in the data statements at the end to suit your needs. The app does not do bounds checking in the plot routine, so after it gets past char 0 (to char -1) it bombs out.

:EDIT: preview image post. Thanks Schema!

Schema · Post by **Schema** » Thu Apr 28, 2011 3:34 pm

Cool!

Boray · Post by **Boray** » Thu Apr 28, 2011 4:04 pm

Looks pretty cool in 2000-3000% speed...

jbevren · Post by **jbevren** » Thu Apr 28, 2011 4:13 pm

Yeah the preview isnt an exact match to the program in the d64. The number that counts down is how many characters are still unallocated.

If you guys have any questions about the way it works feel free to post here. I'll monitor the thread for at least a couple days

Mike · Post by **Mike** » Thu Apr 28, 2011 4:30 pm

Also works fine in MINIGRAFIK (download):

Here's the converted program:

Code: Select all

10 REM ** GINGERBREAD
11 @ON:@CLR
12 READX$,Y1:ON-(X$="END")GOTO14:X1=VAL(X$)
13 FORI=1TO5000:OX=X1:OY=Y1:X1=1-OY+ABS(OX):Y1=OX:@1,X1*11+47.5,Y1*13+57.5:NEXT:GOTO12
14 GETA$:ON-(A$="")GOTO14:@RETURN:END
15 :
16 DATA-3.14,0
17 DATA-0.14,0
18 DATAEND,0
19 :
20 REM ** GINGERBREAD, CONVERTED 2011-04-28 TO MINIGRAFIK BY MIKE

Greetings,

Michael

jbevren · Post by **jbevren** » Thu Apr 28, 2011 6:47 pm

Nice Michael!

For others that arent familiar with minigrafik, dont stumble as I did: the wedge requires 8k or more of expansion.

I couldnt work out why it wouldnt run. However, I kinda wonder why the 1541 goes blinky when it crashes on an unexpanded vic

Mike · Post by **Mike** » Fri Apr 29, 2011 12:48 am

Hi!

jbevren wrote:For others that arent familiar with minigrafik, dont stumble as I did: the wedge requires 8k or more of expansion.

Yes, indeed MG requires at least an +8K RAM expansion. The complete address range of $1000 to $1FFF is used to store the bitmap.

It has been around for quite some time now, though. The original version was written in 1985(!) by W. Wirth, and ran on a unexpanded or +3K VIC-20, but only provided 128x128 pixels. I rewrote it from scratch in 2006 for a resolution of 160x192 and did another update in 2008. You'll find several programs and games here in Denial, which use MG.

I couldnt work out why it wouldnt run. However, I kinda wonder why the 1541 goes blinky when it crashes on an unexpanded vic

It's not a bug, it's a feature.

Post by **Jeff-20** » Fri Apr 29, 2011 10:48 am

Really cool!

rhurst · Post by **rhurst** » Sat Apr 30, 2011 5:13 am

And if you really like 'features', try my stuff.

Using dynamic characters in this manner is slick, nice job. When I look at this fractal, I think of my Droid X phone running Gingerbread. Sweet!

jbevren · Post by **jbevren** » Sat Apr 30, 2011 5:58 pm

A nice feature in my plot subroutine is that carefully crafted coordinates can be used to set specific bits in the I/O hardware (or anywhere in memory for that matter). Top that!