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Forums > C64 Coding > DYPP
2017-03-29 13:36

Registered: May 2010
Posts: 101

DYPP - Different Y Pixel Position.
I don't seem to find an explanation on this effect on C64 on codebase or anywhere. Maybe its in another thread here on csdb, then please provide an link.

I know the basics of sines, ive made sinescroll on PC, but its easier there since you can look up the framebuffer directly, via sine-tables and so on.

Im wondering how this effect is easily made on C64. I believe there are more than one way, but i guess one way is slower than the other; for example moving each column-bit (inside a char) in realtime. The other way I think is having the chars animated, similar to a twister. Though, im thinking each angle is used for lookup table. I just dont seem to get it right in my mind to start coding on this effect. I've seen several early cracktros and demos that does this very fast, but haven't had the time to reverse-engineer the binaries. If you have any tips and info i'd appreciate it, or even better; write an explanation for codebase.
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2017-03-31 10:40

Registered: Oct 2010
Posts: 42
I would do 8 copies of the charset (one for each pixel column) and then just LDA ORA ORA ORA ORA ORA ORA STA.
If you arrange chars nicely, maybe you can unroll the whole thing and do LDY LDA,y ORA,y ... dunno.
Maybe there's better way as well.
2017-03-31 11:37

Registered: Apr 2002
Posts: 4239
better way: speedcode per char, to skip empty pixels.
2017-03-31 12:25

Registered: Jan 2005
Posts: 334
Even better: use VSP, that way the shape of the dypp doesn't actually change and you can optimize a lot of code (no need to clear stuff, perhaps 'join' a few pixels in a single ORA, etc).
2017-03-31 12:53

Registered: Apr 2002
Posts: 4239
Quote: There exists an old, but pretty good DYPP based on VSP in Anal Intruder. And AFAIK the best completely dynamic DYPP is in Mekanix.

mekanix is cheating as far as I'm concerned, lda sta code, no ORA.
2017-03-31 13:28

Registered: Feb 2003
Posts: 671
Quote: mekanix is cheating as far as I'm concerned, lda sta code, no ORA.

Mekanix is using precalculated fonts for a range of angles. It is still calculating individual sinus-values for each pixel-column, and then mapping it to best possible font.. The accuracy is ok i would say :). Also this way it can do more funny sinuses than VSP-stuff.
2017-03-31 20:32

Registered: Jan 2005
Posts: 334
Gotta admit those DYPP's look really smooth, and using a movement you can't get with VSP-trickery.

Never had seen that demo before even, I'm lagging behind badly :)
2017-03-31 20:35

Registered: Aug 2004
Posts: 792
Ah, so that's how they managed such a large area. It's effectively caching intermediates, so that still counts in my book; just restricted to reasonably smooth functions :)
2017-04-01 00:36

Registered: Oct 2005
Posts: 79
I believe The Larch III The Larch 3 had a mega-DYPP in it. The same effect using a 1x1 charset and 8 splits per char without pre-plotting chars would take a massive amount of raster time. Plotting the bits in pairs resulting in 4 different Y positions per char still looks pretty impressive.
2017-04-01 09:26

Registered: Oct 2011
Posts: 26
We are in 2017 and you are talking about keeping lamers out? Sounds like 1989... :-)
2017-04-01 11:36

Registered: Aug 2004
Posts: 792
Well, The Larch 3's from 1989, so I guess that fits at least..

But yeah, I think a somewhat more welcoming attitude to newbies is more important than ever.
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