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Old 25 May 2006, 08:36   #1
alexh
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Vertical Insanity Razor1911

As a hardware engineer I was always curious about the text in the scroller of this demo, talking about an undocumented opcode (Movef) which never existed.

http://www.pouet.net/prod.php?which=4286

Why would they make up such rubbish?

---------------------------------------------

Now Many years later I thought I'd found the answer. I find a C64 demo claiming a similar thing. I started thinking there WERE a lot of undocumented opcodes on the 6502, perhaps this isnt rubbish?

http://www.pouet.net/prod.php?which=15401

The style of the two demo's is identical. One is almost certainly a parody of the other. I started thinking, perhaps Razor 1911 saw this demo, liked it and decided to make a copy.

I then started to wonder which came first and which is a parody of which? It made sense in my mind for the C64 one to be first and the Amiga one to be a piss take, but according to the dates in Pouet the Amiga version was first?

Anyone have any insight into this coding / demo oddity?
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Old 25 May 2006, 14:05   #2
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Quote:
Originally Posted by alexh
I started thinking there WERE a lot of undocumented opcodes on the 6502, perhaps this isnt rubbish?
http://www.google.pl/search?q=undocumented+opcodes+6502
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Old 25 May 2006, 14:57   #3
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btw a wonderful intro with an excellent music by Uncle Tom if i remember right
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Old 25 May 2006, 17:20   #4
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@AGN

I know that there are undocumented opcodes in 6502. But if you have a read you see that undocumented opcode $72 mentioned in the scroller of this demo (sometimes referred to as HALT) crashes the 6502!!

@Frog

Yeah Spell Amelioration, very nice.

Last edited by alexh; 25 May 2006 at 17:31.
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Old 25 May 2006, 17:31   #5
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I still dont know which came first, or if one was a parody of the other... anyone know?

Or why two excellent groups would write stuff in scrollers about undocumented opcodes which *appears* to be rubbish.

Surely Ray "NZO" Norrish or some other sceners know's something?
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Old 25 May 2006, 22:15   #6
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Make that three excellent groups, perhaps it's become a scene tradition (I shall remember this if I ever make a vertical rasterbar part on the Genesis/Megadrive).

Crest also did a similar vertical rasterbar part in Ice Cream Castle, where they also mentioned an undocumented "opcode" used to create vertical bars at a resolution of 1 multicolor pixel. This was released in April 1991, which makes it the last of the three to be released. It bested Megastyle's version, which only used 2-multicolor-pixel wide bars. All faked of course, but in demos you fake what the hardware doesn't normally allow you to do =P
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Old 25 May 2006, 23:08   #7
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Quote:
Originally Posted by alexh
As a hardware engineer I was always curious about the text in the scroller of this demo, talking about an undocumented opcode (Movef) which never existed.

http://www.pouet.net/prod.php?which=4286

Why would they make up such rubbish?

---------------------------------------------

Now Many years later I thought I'd found the answer. I find a C64 demo claiming a similar thing. I started thinking there WERE a lot of undocumented opcodes on the 6502, perhaps this isnt rubbish?

http://www.pouet.net/prod.php?which=15401

The style of the two demo's is identical. One is almost certainly a parody of the other. I started thinking, perhaps Razor 1911 saw this demo, liked it and decided to make a copy.

I then started to wonder which came first and which is a parody of which? It made sense in my mind for the C64 one to be first and the Amiga one to be a piss take, but according to the dates in Pouet the Amiga version was first?

Anyone have any insight into this coding / demo oddity?
The vertical bars in more than 64 colors are 1 line high HAM bobs, stretched down the screen with a simple negative modulo by the copper.

The logo and scroller are sprites, whose colors are unaffected by the HAM mode. These sprites are in fact vertical, but skewed one pixel per line so it would appear they are wider than 16 pixels (each).


So claiming that it's done with undocumented opcodes is a lie meant to fool lamers. It's not the first time it's happened, either. In the demo '420 bobs', Gurk/PHA suggests that the thick pink lines/arcs made up of many pink round bobs is made with the blitter's line drawing mode, while quickly shifting the line Mask...
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Old 26 May 2006, 01:38   #8
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There are plenty of demos where the text describes some bullshit way the effect was acheived - strange really, as the real technique being described would be far more interesting!

Vertical rasters are a nice copper trick I used myself on occasion, but there's no "secret" opcode involved there.
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Old 27 May 2006, 02:30   #9
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You can make it even nicer by using some hardware scrolling and making them "bend" :-)

One thing you can do in fill mode with the blitter is make some simple Sierpinski triangles. I did it in an intro once. a sinus plotted line of pixels with a vertical blitter fill after each plot. rinse and repeat.

(of course i was not the first to do this. i saw another demo do it and just copied.. infact a friend showed me his source which did it and i pretty much stole that )
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Old 27 May 2006, 18:03   #10
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Rebels Total Triple Trouble does the vertical bend bars.
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Old 27 May 2006, 18:52   #11
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And a Vision Factory cracktro which can be found on the frontpage of flashtro.com right now
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Old 27 May 2006, 18:55   #12
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flashtro.com
flashrtro.com = awesome site!
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Old 28 May 2006, 13:38   #13
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Quote:
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Rebels Total Triple Trouble does the vertical bend bars.
a wonderful demo with great copper tricks ! i make an icon for it btw, just in case you wanted to make a whdload fix
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Old 28 May 2006, 14:35   #14
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a wonderful demo with great copper tricks ! i make an icon for it btw, just in case you wanted to make a whdload fix

Yeah, I've done it, just one bug left on o3o
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Old 28 May 2006, 15:20   #15
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cool

http://download.abime.net/pygmicons/PygmIconsGL_D3.lha (glowicon)
http://download.abime.net/pygmicons/PygmIconsNX_D3.lha (newicon)
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Old 30 May 2006, 01:55   #16
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Quote:
Originally Posted by Galahad/FLT
Rebels Total Triple Trouble does the vertical bend bars.
and a whole lot more.. that was one special demo for lots of stuff.
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Old 30 May 2006, 02:03   #17
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vertival wobbly copper

Not as good as ttt, but here's an uncompleted dcs cracktro I was working on in the dim past. Source is available somewhere (I`ll dig it up if anyone is interested).

At least it demostrates the principal in code (both the repeating modulo of the 1 line graphic, and the vertical wobbly itself). It's also a nice design, with closed off borders and sprite logo.

I`ve uploaded it to the zone. Note that it's compiled for an a1200, so needs 2mb chip / a1200 settings in WinUae.
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Old 30 May 2006, 10:01   #18
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move.w #$4489,$dff07e
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That's really nice - I like it a lot
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Old 30 May 2006, 19:46   #19
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Quote:
Originally Posted by Ray Norrish
Not as good as ttt, but here's an uncompleted dcs cracktro I was working on in the dim past. Source is available somewhere (I`ll dig it up if anyone is interested).

At least it demostrates the principal in code (both the repeating modulo of the 1 line graphic, and the vertical wobbly itself). It's also a nice design, with closed off borders and sprite logo.

I`ve uploaded it to the zone. Note that it's compiled for an a1200, so needs 2mb chip / a1200 settings in WinUae.
I have it working in a 0.5mb chip + 0.5mb slow a500 kick 1.3 config

And the source would be a treat
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Old 30 May 2006, 21:40   #20
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interesting, cos it's using $172000 for the screen
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