Would an accurate port of the original Xevious arcade be viable on the A500?

[ImmortalA1000]

Because the only maps of the game I could find were saved as crappy lossy JPEGs bit stuffed for a quick look at palette issues myself so I would have to do an uncompressed recording of a cheat enabled MAME session just to check that. Bit of a faff!

[ImmortalA1000]

I found some background maps on one site, the sprites on another. Stitching area 3, 4 and 5 together gave me 35 colours, using HAMconvert set to 32 colour OCS indexed mode I got the following 30 colour image (count colours function of Paintshop Pro).

The only sprite that isn't like 8 grey scales is the big spaceship which is sort of gold colour, otherwise it's usually less than 32 colours total for multiple maps.

(output attached)

[Retro1234]

Originally Posted by jotd

Well, it's not that easy for a 1:1 port because of the strange local palettes the game uses.

Game uses 128 colors, which could be reduced but it also has an OSD. ATM I'm focusing on an AGA port which should run on bare A1200. There are also memory constraints because of all the lookup tables and various palettes to emulate.

This project was initiated by Mark McDougall, a talented coder who is doing the NeoGeo version which is way beyond the amiga version, but the cool thing is: I don't have a clue about how the game works. All Z80 to 68k reverse of the game logic is done by Mark and I "just" have to implement the hardware dependent calls that he designed.

So more like an emulator, but not as slow as MAME, else it would be useless.

http://retroports.blogspot.com/

Here's a WinUAE video to prove the concept. It's highly buggy (lots of gfx glitches) but you get the idea:

[ Show youtube player ]

Wow! Well done how many colour are the graphics you're using there?

[jotd]

The palette is 128 colors. foreground OSD uses 1 bitplane, playfield uses 7 bitplanes.

This can probably be reduced to 6 bitplanes (probably speeding up the game in the process), allowing foreground OSD to use 2 bitplanes and have more colors. There's currently a hack: colors 128 to 255 are white so the foreground OSD remains white no matter the colors of the background playfield.

On the title screen a copper trick allows the title to flash in multiple colors.

32 colors would mean even more color reduction and total integration of the OSD in the playfield, or that would mean only 16 colors (+ sprites). There aren't many scrolling games having an OSD status screen because it's annoying to make up for the scrolling. Maybe SWIV? Hybris? Battle Squadron? And I suspect they're using dual playfield + multiplexed sprites to get more colors, something that I really can't do with Xevious, which isn't an amiga-specific game:

- each background tile can have any 4-color combination among 128 fixed colors
- each tile is 8x8 which is a nightmare for the amiga because the blitter can't be used efficiently
- each sprite (there are 64 sprites!!) can have any 8-color combination among 128 fixed colors.
- there's a OSD using 1 color per tile but each tile can have a different color!!

perfect for MAME maybe For AGA there's already some compromises... I wanted to use dual playfield 16+16 colors to be able to render sprites/bobs on a different playfield, leaving the background on another playfield (less background restore, did that with Scramble, but a lot less colors) that would mean use 16 colors for background and 16 for sprites, so degrade colors heavily and still require AGA... I decided against it and I'm quite happy with that ATM.

[Retro1234]

Thanks for the reply - what spec are you running that example on?

[jotd]

WinUAE fastest possible, but it runs the same on A1200 speed. But we know that WinUAE is not bothered by slow chipmem. Will have to test it on my real unaccelerated A1200/020, where Scramble already stuttered slightly on the scrolling... (I have to fix that)

[Photon]

I guess if you want the original there's nothing that can replace it, but not only were there quite decent 8-bit ports of this early arcade games, but there were also improved versions on the theme vertical scroller on virtually every platform. When I see this I think of an Apple II game I played ~1983, and Hybris (and before that, Sidewinder, Star Force, etc.)

I'm a great fan of 1984-1988 arcade games, that's when some ideas started to come in. Before that there are some classics of course, not least by Atari Games. And in 1992+ it all turned to fighting games with the odd shooter or driving game. Nobody wanted ideas.

Many of the games before 1984 are too simplistic for me to enjoy now, but there are some. The game loop should pose no problem, or the sound reproduction. Nor the graphics, but that's where accuracy comes in. If the gameplay is addictive, it's addictive in 8 colors. Or 2 colors. If you however hold the Amiga ransom to the per-game random chip sandwich, you can run out of playfields or sprites.

Whereas when they made the game, they too ran out of sprites and playfields and just added more to the prototype.

So here, there is no problem making an exact shooter that plays like this with plenty of wonderful colors on Amiga. Only if you demand it be exactly color-accurate must you use bobs instead of sprites and use RAM the arcade game didn't have.

[tcdev]

Originally Posted by ImmortalA1000

I found some background maps on one site, the sprites on another. Stitching area 3, 4 and 5 together gave me 35 colours, using HAMconvert set to 32 colour OCS indexed mode I got the following 30 colour image (count colours function of Paintshop Pro).

I have BMP (non-compressed) files I've generated for all of the areas, and the entire map as a whole. I've also done some palette analysis on the map...

The background (map) uses only 24 colours. Of those, 5 are used in less than 1,000 pixels, mainly as anti-aliasing, and could be replaced and be hardly noticed. It wouldn't be too difficult to optimise the palette to just 16 colours I wouldn't think.

Xevious was also released on the Namco Classics Vol 1 PCB, which uses a Yamaha YGV608 Display Processor. The aesthetics for that version are noticeably different from the original, I suspect with a reduced palette.

[jotd]

... but the sprites use a different set of colors, So if we had 16 colors for tiles we'd need 16 colors for sprites, in a different playfield (32 color AGA game, super-fast even without sprites thanks to 2 playfields independence, and handle OSD somehow...) or on the same playfield (32 color ECS) (and the OSD is also an issue).

I really have a dilemna with that one. And I haven't started to try to reduce the colors.

[saimon69]

Well Xevious ships are mostly metalic grey with the red glow - and solvalou is white with blue stripes so you might do 32 colors and last 16 shared in background and foreground
(includes the greys and glowing red for enemies)
The Andor Genesis [boss] is however a bit of a problem: for OCS/ECS i would make it grey/dark grey rather than green

[Pyromania]

Parts of this game still look cool but some look pretty dated. An enhanced Amiga or Vampire version could be way better in 2023. I'm talking nice intro screen, nice cut aways, enhanced ships and enemies, etc.

[tcdev]

Originally Posted by Pyromania

Parts of this game still look cool but some look pretty dated. An enhanced Amiga or Vampire version could be way better in 2023. I'm talking nice intro screen, nice cut aways, enhanced ships and enemies, etc.

There's always the Arrangement version from Namco Classics. That's already 68K...

[idrougge]

Originally Posted by Pyromania

Parts of this game still look cool but some look pretty dated. An enhanced Amiga or Vampire version could be way better in 2023. I'm talking nice intro screen, nice cut aways, enhanced ships and enemies, etc.

And make it 3D… And add a copper rainbow… And a CD soundtrack…

The austerity of Xevious is what makes it Xevious.

[h0ffman]

Seems like quite a good match for the system I built for knightmare.

[A500]

Originally Posted by jotd

This project was initiated by Mark McDougall, a talented coder who is doing the NeoGeo version which is way beyond the amiga version, but the cool thing is: I don't have a clue about how the game works. All Z80 to 68k reverse of the game logic is done by Mark and I "just" have to implement the hardware dependent calls that he designed.

So more like an emulator, but not as slow as MAME, else it would be useless.

http://retroports.blogspot.com/

Here's a WinUAE video to prove the concept. It's highly buggy (lots of gfx glitches) but you get the idea:

[ Show youtube player ]

Holy sh*t, I can't believe this is really happening!! Fantastic! Thank you guys

Also, I don't mind if it's AGA machines only if that's what it takes to bring the original experience to the Amiga. This feels like Christmas to me

[jotd]

Originally Posted by h0ffman

Seems like quite a good match for the system I built for knightmare.

yes, slow vertical scrolling, shooter. Looks like it

I wonder how games manage OSD and background layers. For instance do Hybris/Battle Squadron/SWIV use dual playfield? How do they manage OSD?

Using dual playfield makes a huge difference in performance because you don't have to restore the background when moving bobs, just blank it.

I know there's a trick on SWIV to exploit an undocumented ECS feature to create a gradient in score (AGA can't replicate it).

[acidbottle]

Outstanding work to get this off the blocks. Looking great already, despite the glitches!

[Pyromania]

Spwaking about Hybris/Battle Squadron, they are way better than Xevious.

[saimon69]

Battle Squadron is seven years younger than Xevious, but the latter is an icon and part of the "must have" arcade ports for a game machine to be taken seriously

[Galahad/FLT]

Originally Posted by jotd

Well, it's not that easy for a 1:1 port because of the strange local palettes the game uses.

Game uses 128 colors, which could be reduced but it also has an OSD. ATM I'm focusing on an AGA port which should run on bare A1200. There are also memory constraints because of all the lookup tables and various palettes to emulate.

This project was initiated by Mark McDougall, a talented coder who is doing the NeoGeo version which is way beyond the amiga version, but the cool thing is: I don't have a clue about how the game works. All Z80 to 68k reverse of the game logic is done by Mark and I "just" have to implement the hardware dependent calls that he designed.

So more like an emulator, but not as slow as MAME, else it would be useless.

http://retroports.blogspot.com/

Here's a WinUAE video to prove the concept. It's highly buggy (lots of gfx glitches) but you get the idea:

[ Show youtube player ]

OSD? Overlay sprite display???