Would an accurate port of the original Xevious arcade be viable on the A500? - Page 4

lmimmfn · 08 February 2023, 02:08

Excellent jotd, really looking forward to thus, always wanted to play a decent conversion, the Amstrad CPC version is junk, fingers crossed for a proper miggy version.

Pyromania · 08 February 2023, 03:23

When is it coming out?

jotd · 08 February 2023, 10:38

it will still take a while. The sound is nonexistent for instance. And there are a lot of glitches to fix (first: find a way to do that properly). Plus the neogeo part isn't complete if I understand Mark (tcdev) properly.

Hopefully before summer.

tcdev · 08 February 2023, 14:15

Quote:

Originally Posted by jotd

it will still take a while. The sound is nonexistent for instance. And there are a lot of glitches to fix (first: find a way to do that properly). Plus the neogeo part isn't complete if I understand Mark (tcdev) properly.

There are 6 remaining known bugs in the gameplay. Right now I'm in the process of an 'audit' of the transcode, and am fixing known bugs as I encounter the relevant code during the audit. I'd expect the process to take another few weeks at most until the Neo Geo is 100% complete except for sound.

Once the audit is complete I'll switch to supporting jotd where I can and then we'll likely add sound support in parallel to our respective ports.

Tsak · 08 February 2023, 17:03

Quote:

Originally Posted by tcdev

Wow, this is awesome guys, it's going to look great!

Once a reduced palette has been finalised, I might even add it as an option to the Neo Geo version, as you have oodles of graphics ROM space and two banks of palette data (I'm only using one atm).

Just wondering now which other 68K platforms will be viable with a reduced palette... X68000, Genesis? ST?

X68000 should eat this game for breakfast (color and processing wise), just like Neo-Geo, no need for any reduced palettes there. Genesis should also be pretty capable of an 1-1 version given you can display (around) 64 colors at once. You only need to split the palettes to 4 16 color ones. The only downside is you're limited to a 512 overall palette (unlike amiga which has 4096 colors available). So for a version of Xevious you might need to change some color values to match the Genesis palette and then make sure each tile or sprite only uses one of the 4 palettes. So overall a different set of gfx and approach is needed for best results on Genesis vs Amiga.

jotd · 17 February 2023, 20:53

Another video for the WIP version for A1200. Running from winuae with A1200 speed.

[ Show youtube player ]

TCD · 18 February 2023, 09:20

Looks promising

Is the 'stutter' of the background performance related or is there a different reason for it?

jotd · 18 February 2023, 15:16

The objects in the background that you can bomb are also sprites. Since background is scrolling, the game is emulating the moving position by changing sprite Y.

This is also visible in MAME, albeit slightly less. Since the game is a Z80 to 68k transcode for NeoGeo then ported to Amiga, such issues may occur.

I still have to figure out a way to filter this bad visual effect.

TCD · 18 February 2023, 16:30

Thank you for the explanation

I haven't played the game often so I didn't notice it happening in MAME.

Quote:

Originally Posted by jotd

I still have to figure out a way to filter this bad visual effect.

Good luck

A500 · 18 February 2023, 18:45

Quote:

Originally Posted by jotd

Another video for the WIP version for A1200. Running from winuae with A1200 speed.

[ Show youtube player ]

Thanks for the update!

pink^abyss · 18 February 2023, 19:48

[QUOTE=jotd;1593313
- each tile is 8x8 which is a nightmare for the amiga because the blitter can't be used efficiently
[/QUOTE]

I remember for Tinyus I also had 8x8 tiles to handle. I used the cpu to copy merged 16x8 tiles. I think I needed only to copy one 16x8 tile each frame because the game scrolled very slow.

4bpl would e a good choice for OCS. Later in the game quite a few larger enemies are on screen. I think the blitter would not be able to make it all at 50fps with 5bpl. The score and own ship can be all done by sprites. So a good 16 color palette would allow a near 1:1 conversion.

jotd · 18 February 2023, 22:22

Since I'm using dual playfield I don't have to blit the tiles several times to restore the background. So 8x8 tiles is okay, using CPU. Your solution looks good (but tricky to implement probably)

Foreground tiles are 1-bitplane, and rarely used in the screen. So updating them with the CPU isn't a big problem either.

Now for OCS, 16 colors for 1:1 is probably not going to cut it. I have a hard time fitting all colors in 32 colors of AGA dual playfield. Using sprite palette helps slightly but this isn't going to handle the general case. There are a lot of objects on screen

And also: I'm not as talented as you are. And not my choice of conversion, doing a port of a Z80 transcode that isn't compatible with amiga hardware. So maybe there will be an ECS port, which will be 16 colors DPF and pretty much washed off

pink^abyss · 19 February 2023, 05:25

Quote:

Originally Posted by jotd

And also: I'm not as talented as you are. And not my choice of conversion, doing a port of a Z80 transcode that isn't compatible with amiga hardware. So maybe there will be an ECS port, which will be 16 colors DPF and pretty much washed off

Thanks for your kind words

tho for Tinyus it was also the talent of Fade1 who was amazing in retouching the graphics. Also without Bartmans C/C++ environment I would have never been brave enough to start. Im sure you will do a super accurate port with your design!

tcdev · 19 February 2023, 12:57

Quote:

Originally Posted by jotd

This is also visible in MAME, albeit slightly less. Since the game is a Z80 to 68k transcode for NeoGeo then ported to Amiga, such issues may occur.

It is still possible that the scheduling of the MAIN and SUB CPU programs with respect to the VBL can be tweaked to reduce this effect. TBA.

jotd · 19 February 2023, 13:00

Quote:

Originally Posted by pink^abyss

Thanks for your kind words

tho for Tinyus it was also the talent of Fade1 who was amazing in retouching the graphics. Also without Bartmans C/C++ environment I would have never been brave enough to start. Im sure you will do a super accurate port with your design!

Yes, Mark is a very strict adept of Z80 transcoding, so all enemy moves & shots are accurate (which is something that some people will blame you for if you're rolling your own moves on such an iconic game)

I'm a fan of all-assembly (got enough high level languages at work, and got really disappointed by the performance of my Bagman C++ amiga port). I won't retouch the graphics except for color reduction/quantization done by my pre-processing python script. If I can use AGA sprites with a different palette, this end boss will look magnificent.

I'll take you up to the challenge of shoehorning this game 1:1 on 16 colors ECS though

even using sprites that would be not a piece of cake.

Quote:

Originally Posted by tcdev

It is still possible that the scheduling of the MAIN and SUB CPU programs with respect to the VBL can be tweaked to reduce this effect. TBA.

I've already tried a few things like adding/subbing offsets... to ground objects, to no avail. An improvement by your end would certainly be welcome!!

pink^abyss · 20 February 2023, 16:17

Quote:

Originally Posted by jotd

I'll take you up to the challenge of shoehorning this game 1:1 on 16 colors ECS though

even using sprites that would be not a piece of cake.

Hehe.. I would add to the challenge to make it in 32Kb. However, the Gradius conversion was mainly motivated by the great music, something that doesn't work for me with Xevious..

jotd · 20 February 2023, 16:22

Xevious music is just pure crap... But remakes include good music it seems.

I dug into trying to make it faster though. Found a few ways to optimize the game

- first, I did a second update every 5 update to emulate 60Hz, but I forgot that the update also redrew everything, which is useless. Skipped one redraw => a lot of useless blits => speed gain

- all sprites are 16x16 (as designed in the arcade game). But a lot of sprites are small (bullets). So reducing the height of some sprites allow to save blitter bandwidth. I have to stop reasoning like if I was coding an emulator.
- if needed I can skip one more frame. It won't be 50Hz but removes flicker
- the frameskip can be dynamic: if too many objects active on screen, enable it, else leave it alone.

Cris1997XX · 22 February 2023, 00:30

Quote:

Originally Posted by jotd

Xevious music is just pure crap... But remakes include good music it seems.

I dug into trying to make it faster though. Found a few ways to optimize the game

- first, I did a second update every 5 update to emulate 60Hz, but I forgot that the update also redrew everything, which is useless. Skipped one redraw => a lot of useless blits => speed gain

- all sprites are 16x16 (as designed in the arcade game). But a lot of sprites are small (bullets). So reducing the height of some sprites allow to save blitter bandwidth. I have to stop reasoning like if I was coding an emulator.
- if needed I can skip one more frame. It won't be 50Hz but removes flicker
- the frameskip can be dynamic: if too many objects active on screen, enable it, else leave it alone.

Can't you just use hardware sprites for the Souvalou and enemies' bullets? I think it would save a lot of bandwidth that way

metalion · 24 February 2023, 17:02

I never thought an Amiga 1200 was in trouble to run Xevious, my humble MSX2 has a very good port, maybe the best port non emulated.

[ Show youtube player ]

CCRider · 24 February 2023, 17:59

Quote:

Originally Posted by metalion

I never thought an Amiga 1200 was in trouble to run Xevious, my humble MSX2 has a very good port, maybe the best port non emulated.

[ Show youtube player ]

Fudeba go home.

08 February 2023, 02:08	#61
lmimmfn Registered User Join Date: May 2018 Location: Ireland Posts: 691	Excellent jotd, really looking forward to thus, always wanted to play a decent conversion, the Amstrad CPC version is junk, fingers crossed for a proper miggy version. Last edited by lmimmfn; 08 February 2023 at 11:38.

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08 February 2023, 03:23	#62
Pyromania Moderator Join Date: Jan 2002 Location: Chicago, IL Posts: 3,390	When is it coming out?

08 February 2023, 10:38	#63
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,369	it will still take a while. The sound is nonexistent for instance. And there are a lot of glitches to fix (first: find a way to do that properly). Plus the neogeo part isn't complete if I understand Mark (tcdev) properly. Hopefully before summer.

17 February 2023, 20:53	#66
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,369	Another video for the WIP version for A1200. Running from winuae with A1200 speed. [ Show youtube player ]

18 February 2023, 09:20	#67
TCD HOL/FTP busy bee Join Date: Sep 2006 Location: Germany Age: 46 Posts: 31,975	Looks promising Is the 'stutter' of the background performance related or is there a different reason for it?

18 February 2023, 15:16	#68
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,369	The objects in the background that you can bomb are also sprites. Since background is scrolling, the game is emulating the moving position by changing sprite Y. This is also visible in MAME, albeit slightly less. Since the game is a Z80 to 68k transcode for NeoGeo then ported to Amiga, such issues may occur. I still have to figure out a way to filter this bad visual effect.

18 February 2023, 19:48	#71
pink^abyss Registered User Join Date: Aug 2018 Location: Untergrund/Germany Posts: 410	[QUOTE=jotd;1593313 - each tile is 8x8 which is a nightmare for the amiga because the blitter can't be used efficiently [/QUOTE] I remember for Tinyus I also had 8x8 tiles to handle. I used the cpu to copy merged 16x8 tiles. I think I needed only to copy one 16x8 tile each frame because the game scrolled very slow. 4bpl would e a good choice for OCS. Later in the game quite a few larger enemies are on screen. I think the blitter would not be able to make it all at 50fps with 5bpl. The score and own ship can be all done by sprites. So a good 16 color palette would allow a near 1:1 conversion.

18 February 2023, 22:22	#72
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,369	Since I'm using dual playfield I don't have to blit the tiles several times to restore the background. So 8x8 tiles is okay, using CPU. Your solution looks good (but tricky to implement probably) Foreground tiles are 1-bitplane, and rarely used in the screen. So updating them with the CPU isn't a big problem either. Now for OCS, 16 colors for 1:1 is probably not going to cut it. I have a hard time fitting all colors in 32 colors of AGA dual playfield. Using sprite palette helps slightly but this isn't going to handle the general case. There are a lot of objects on screen And also: I'm not as talented as you are. And not my choice of conversion, doing a port of a Z80 transcode that isn't compatible with amiga hardware. So maybe there will be an ECS port, which will be 16 colors DPF and pretty much washed off

20 February 2023, 16:22	#77
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,369	Xevious music is just pure crap... But remakes include good music it seems. I dug into trying to make it faster though. Found a few ways to optimize the game - first, I did a second update every 5 update to emulate 60Hz, but I forgot that the update also redrew everything, which is useless. Skipped one redraw => a lot of useless blits => speed gain - all sprites are 16x16 (as designed in the arcade game). But a lot of sprites are small (bullets). So reducing the height of some sprites allow to save blitter bandwidth. I have to stop reasoning like if I was coding an emulator. - if needed I can skip one more frame. It won't be 50Hz but removes flicker - the frameskip can be dynamic: if too many objects active on screen, enable it, else leave it alone.

24 February 2023, 17:02	#79
metalion Registered User Join Date: Dec 2020 Location: São Paulo / Brazil Posts: 2	I never thought an Amiga 1200 was in trouble to run Xevious, my humble MSX2 has a very good port, maybe the best port non emulated. [ Show youtube player ]

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