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Software:demoscene:Copper by Surprise Productions (1992)

Robert de Rooy edited this page Feb 4, 2023 · 5 revisions

1992 demoscene entry.

Demo description

Proof of concept of VGA raster tricks with Adlib FM synthesizer music.

[dosbox]
memsize=1
machine=vgaonly
allow hretrace effects=true

[cpu]
core=normal
cputype=386
cycles=4000

[sblaster]
sbtype=sbpro2

VGA raster tricks used in the demo

This demo employs a lot of VGA raster trickery, in addition to the usual changing the color palette per scanline to make copper bars. The most dangerous trick not likely to work with today’s monitors is to make the picture waver by changing the position of the horizontal sync pulse once per scanline. That trick may happen to work with older VGA CRT monitors, but will cause modern flat panels and scan converters to blank the picture.

Adlib FM synthesizer music

The demo will autodetect and use the Adlib FM synthesizer of your sound card. The detection however is CPU speed sensitive. If the cycle count is 13000 or higher, detection will fail, and you will hear no music. Music tempo is tied to the VGA refresh rate. If the refresh rate is anything other than 70Hz music will play too fast or too slow.

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