Syntax Infinity Twister Effect

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Por killimolli

Supporter (14)

imagem de killimolli

30-05-2009, 09:37

Hello,

Im just a MSX fan from Finland. My first computer was Canon MSX(V20). I bought it 1986, dont ask the price, it was expensive here in Finland. However, especially that model always will have special place in my heart.

Yes, i still play my favorite games with BlueMSX(sorry OpenMSX).

Systeemi-muuttuja Jiffy? Kukas se oli joka piti mikrobittii msx palstaa? Smile

Above one is only for NYYRIKKI Smile

Anyway, about the fantastic Syntax Infinity demo and the twister effect.
Im not a coder but can someone explain how that effect is made and why its so smooth. Is it an animation or stuff like that? Damn it looks like it was made on PC.

-killimolli

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Por Manuel

Ascended (19270)

imagem de Manuel

30-05-2009, 13:30

Roughly speaking, it probably uses a line interrupt on each line and then selects the proper line from the other screen, where a bitmap is positioned with all possible lines from the effect. Many effects like this are done in this way, e.g. Unknown Reality has several of those as well and other demos too.

Por Edwin

Paragon (1182)

imagem de Edwin

30-05-2009, 18:13

For those not familiar with MSX registers. Basically it selects a new vertical scroll position after every line. So basically you can do it by having a large table of scroll data and outputting that line after line, frame after frame. Of course, I assume that the selection of data is somewhat smarter than that. The biggest problem of course it making a good looking sequence.

Por NYYRIKKI

Enlighted (6016)

imagem de NYYRIKKI

30-05-2009, 18:44

1. #FC9E (Canon V-20 manual rocks, it's the best I've seen!)
2. Can't recall... too much time has passed...

Por bore

Master (161)

imagem de bore

30-05-2009, 18:54

"The biggest problem of course it making a good looking sequence."

Actually that was the second biggest problem, the biggest problem was to compress the bitmap data into a small enough memory block.
Overall I think I spent more time writing data generators and unpackers than actual effects.

And yes, the twistbar pretty much work like manuel and edwin explained.

Por Hrothgar

Champion (479)

imagem de Hrothgar

30-05-2009, 22:27

Interesting. I didn't find that twister effect all that special and have seen similar effects before on MSX and other 8-bit computers. Indeed knowing what hardware trick is used takes away a bit of the magic :-)

What I did find interesting is the speed and relative smoothness of the wire graphics in the intro sequence. How can you draw skewed lines on a coloured background and - more importantly - have the background restored the next frame that fast?

Por Edwin

Paragon (1182)

imagem de Edwin

30-05-2009, 23:34

Hrothgar> Also a fairly simple trick (the one I used way back). Draw the bitmap using only colour 0-7. Make colours 8-15 line colours. Draw lines using XOR with with colour 8. And again to remove the line.

Por AuroraMSX

Paragon (1902)

imagem de AuroraMSX

31-05-2009, 11:40

Hrothgar> Also a fairly simple trick (the one I used way back). Draw the bitmap using only colour 0-7. Make colours 8-15 line colours. Draw lines using XOR with with colour 8. And again to remove the line.And *poof!* another bit of demo magic gone Tongue

Por wolf_

Ambassador_ (10088)

imagem de wolf_

31-05-2009, 11:56

He's like the masked magician! Tongue

Por Hrothgar

Champion (479)

imagem de Hrothgar

31-05-2009, 12:23

Thanks for explaining Edwin. Makes perfect sense, if you know the powers of the VDP. Contrary to the twister effect (that can probably be done by any computer using line interrupts and scrolling registers) it looks like this trick isn't as widely usable on retro systems other than MSX2?

There might also be possibilities to use this effect in games instead of demos by the way. I can't currently think of any title that uses this.

Por wolf_

Ambassador_ (10088)

imagem de wolf_

31-05-2009, 12:38

Typical 'hacky' demo effects are greatly impractical for games, I think. Screensplits, colorsplits and scrollsplits *are* practical for games.

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