Comments on: JavaScript Raster Bar Effect

By: Diodeus

Diodeus — Wed, 17 Dec 2008 13:50:00 +0000

sys 64802

By: aurora

aurora — Wed, 17 Dec 2008 08:21:47 +0000

nice one!

By: Breton

Breton — Wed, 17 Dec 2008 05:54:36 +0000

hei wait a second, I’m pretty sure “RasterBar” is not a built in type, and I don’t see it defined anywhere in that code. What are you trying to pull here?

By: ThomasHansen

ThomasHansen — Wed, 17 Dec 2008 01:10:05 +0000

@cromwellian
— *RESPECT*…!! :P

By: rlopes

rlopes — Wed, 17 Dec 2008 00:40:23 +0000

That’s what I have been growing up with and these hacking days still influence me today.
Many among the best are from this period.

Great !

By: cromwellian

cromwellian — Tue, 16 Dec 2008 21:37:49 +0000

Yeah, 6502 doesn’t even have sin/cos unless you want to do powerseries expansion. I would typically write a short basic program to generate a table by poking values into memory at $c000, and then I’d use an ML monitor to hex dump these into ASM data sections.

My favorite table was to use an exponentially decaying cosine table to implement a ‘bounce’ gravity effect, something like

for i = 0 to 4
for j = 0 to 64
poke 49152 + i * 64 + j, cos(j/64 * pi/2) / exp(i)
next j
next i

(apologies, I forgot most of basic)

By: PieturP

PieturP — Tue, 16 Dec 2008 21:02:47 +0000

Whoops, didn’t read cromwellian well enough…

By: PieturP

PieturP — Tue, 16 Dec 2008 21:01:37 +0000

You wouldn’t use cos/sin Math, but use a lookup table instead ;-)

By: Spocke

Spocke — Tue, 16 Dec 2008 20:33:02 +0000

Yeah! Retro. This brings me back to the good old days. jmp #fc0000

By: starkraving

starkraving — Tue, 16 Dec 2008 19:52:55 +0000

And you tell that to the young kids of today, and they won’t believe you…

By: cromwellian

cromwellian — Tue, 16 Dec 2008 18:57:53 +0000

Amiga? Atari? Bah, these machines were much too powerful for Raster Bars, like having a Copper chip coprocessor to doing them. Back in the Commie 64 dayz, we did it the hard way, with cycle accurate delay timing of register pokes, and the code was smaller! :)

wait lda $d012
cmp #$20
bne wait
ldx #$0
loop lda colorTable, x
sta $d020
ldy delayTable, x
spin dey
bne spin
inx
cpx #8
bne loop

(ok, you wouldn’t use lda $d012/cmp/bne, but use a raster interrupt)