Cordoomceps – Replacing an Amiga’s brain with DOOM

https://mjg59.dreamwidth.org/73001.html

by naves • 12 months ago

47 13 12 months ago

mjg59.dreamwidth.org

ekianjo• 12 months ago

this deserves a video at the end.

vidarh• 12 months ago

Given we have AROS, that is mostly AmigaOS compatible and has an ARM port, and that also has a classic Amiga port, it'd be fun to see the ARM version of AROS ported to this...

Sheeplator• 12 months ago

So the Amiga is a graphics card for Doom running on the Pi. Can we make that general purpose? Does Linux still have Amiga drivers?

mjg593• 12 months ago

I considered this and it's slightly awkward - the hardware isn't memory mapped so the drivers would all need to be adapted, and there's no realistic way it'd get upstream. There's also the problem that the Amiga is big endian and Linux on the Pi is little endian so even if you could memory map it you'd still need to byte swap everything. Not literally impossible, but a giant pain.

jrmg• 12 months ago

Would it be possible (and/or a good idea...) to calculate the best HAM approximation of the frame, rather than an EHB version?

mjg593• 12 months ago

Given there's no need to run any code on the 68K bus it's probably actually possible to do the palette calculations per line and use the copper to reprogram the colour registers every line, getting way more colours than plain EHB without the HAM side-effects

nxobject• 12 months ago

"Racing the scanline"?

egypturnash• 12 months ago

This was known as “Sliced HAM” back in the day. I don’t recall anyone doing anything more than pre-processed still images with it though I wouldn’t be surprised to see a few demos with some real-time SHAM effects.

mjg593• 12 months ago

Hmm actually the Copper probably isn't fast enough for this - it takes about 8 pixel scanout equivalent to update one register, and hblank isn't going to be large enough to update all of them. But Copper's performance is restricted by having to read instructions out of RAM before executing them, so if I just use another core on the Pi to read the scanout location I can have that update the palette during scanout much faster without blocking the main thread from continuing to render the next frame.

Findecanor• 12 months ago

The way HAM works, a pixel can be either one of only 16 colours, or the colour of the pixel to the left and change one component: red, green or blue.

Back in the day, I used a program that loaded GIFs in 256 colours and converted them to HAM. The resulting images had lots of edge artefacts, and that is what I would expect out of that too.

amiga3862• 12 months ago

Like a Vampire but with honest intentions. It accepts it is wearing the Amiga as a hat.

Cordoomceps – Replacing an Amiga’s brain with DOOM

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