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 Post subject: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Dec 31, 2018 5:25 pm 


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Hi everyone,

there's one thing which is driving me nuts and it's that there are small graphical glitches which happen on original hardware which are not reproduced in MAME (using the same ROMs).

I've tested and doublechecked everything and all is good and tight.

On youtube I managed to find only one guy which recorded the game from original hardware and, lo and behold, he has the exact same graphical glitches I have.

The glitches I've encountered so far are:

1 - During the attract mode (not shown in the video), upper part (the one with the score, etc...), some small horizontal black lines flickering when the image changes.

2 - When you start playing, before you take control of Opa-Opa, there are the same small horizontal black lines in the middle of the screen: https://youtu.be/vucC5RDi-Xg?t=13

3 - During the 4th zone boss, when you get closer to the boss and start attacking rapidly, the boss' sprite gets slightly corrupted: https://youtu.be/vucC5RDi-Xg?t=505

4 - Not shown in the video, but sometimes I manage to corrupt part of the shop graphics which will show some big white boxes going over the interface. I don't have a reliable way to trigger this, but it seems that if I shoot a lot and there are lots of sprites on screen when I open the shop, this will happen.

Apart from this last one, the other glitches can be reliably reproduced and are always the same: same lines, same spot, same duration, etc.

None of this happens in MAME or in the PS2 collection from which the ROMs are extracted.

I thought I messed up something, but since I've found another guy with the *exact same glitches* I have, I think there might be something wrong in the ROMs... maybe bad dumps?

Please, let me know if you have a working board if you have those glitches as well.

I might upload a better video to show you those issues at a later time.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Dec 31, 2018 7:50 pm 



Joined: 11 Nov 2013
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Not to derail too much, but I thought Fantasy Zone II was only available for the System E boards, not 16c?

EDIT: NM, this is the DX version done by M2, not the original.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Dec 31, 2018 11:19 pm 


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Just curious though

Aside from the glitches
Are there any differences between playing this on original hardware vs the PS2 collection?


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Tue Jan 01, 2019 12:08 pm 


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Haven't played the PS2 version yet, just watched it on youtube, but the data is the same. If you unpack the PS2 ISO, you find the game's ROMs.

The emulator on PS2 probably sets a dipswitch to freeplay and that should be all the differences you get.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Tue Jan 01, 2019 12:19 pm 


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Now that I think about it I wonder if there's any lag at all with the PS2 emulation. Wonder if anyone would be interested in comparing this at all.

I'm happy with the PS2 seeing how I have it hooked up to a really nice CRT and the game outputs 240p beautifully on my Sony WEGA. Got my shmup stick for my PS2 as well and I'm all set to emulate that arcade experience at home :D


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Tue Jan 01, 2019 6:58 pm 


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Eh, guess I could try a giving it a go, but right now the point of the thread is understanding why the hell those graphical glitches happen and if it's normal or something is amiss.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 2:33 am 



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@Shel: the unique nature of FZIIDX means that, strictly speaking, the PS2 version is the original and not the board. M2 created the game specifically for the PS2 collection, aiming to capture the nature of the game if it had been built for System 16. The specs for this game include far more RAM than any of the actual S16 games had. The limited boards built were sort of promotional/exhibition items and were retrofitted around the game M2 had come up with.

So of course, the experience on an actual board is something to be interested in, but you don't have to worry about "emulation quality" in this case - you're definitely playing the game as intended by its creators the first time around.

@don: I don;'t have a factual answer for you, but I have to wonder if the glitching you describe - expecially since you cite at least one identical example - is entirely normal and due to the unique nature of these boards as described. Since they weren't mass-produced and had some unique components, perhaps this led to some quirks in the final boards?


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 3:22 am 


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Not worried about emulation quality at all but was curious as to see if lag did exist in the PS2 collection.

It was a curiosity thing to be honest :)


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 12:09 pm 


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bigbadboaz wrote:
@Shel: the unique nature of FZIIDX means that, strictly speaking, the PS2 version is the original and not the board. M2 created the game specifically for the PS2 collection, aiming to capture the nature of the game if it had been built for System 16. The specs for this game include far more RAM than any of the actual S16 games had. The limited boards built were sort of promotional/exhibition items and were retrofitted around the game M2 had come up with.


I'm 100% positive it's exactly the other way around: I've read several times that M2 developed the game for the S16 system, but since it was able to address way more memory than it originally could, they decided to take advantage of it and build the game upon an improved board codenamed "HOSII" and then dubbed "System16C" which ran with 256KB of RAM and 8KB of Z80 RAM (with the latter being already on the board, as the game audio runs fine without any further modification).
Then they made an emulator for it on the PS2 and that was pretty much it.

Quote:
So of course, the experience on an actual board is something to be interested in, but you don't have to worry about "emulation quality" in this case - you're definitely playing the game as intended by its creators the first time around.


I kind of agree, as they probably made an emulator specifically for this game.

Quote:
@don: I don;'t have a factual answer for you, but I have to wonder if the glitching you describe - expecially since you cite at least one identical example - is entirely normal and due to the unique nature of these boards as described. Since they weren't mass-produced and had some unique components, perhaps this led to some quirks in the final boards?


That's what I was thinking and what's irking me even more is that there's no footage of those boards running to see if the glitches appeared also on the "official" System16C.
To me it almost looks like that the glitches are either:

1 - The machine hitting the sprite limit, just like old NES did
2 - RAM or EPROMs not fast enough, but, hell, I've used the fastest I could find around, way faster than original System16 roms. And, just to rule this out, those RAMs and EPROMs work fine with other System16B games, no glitches at all.

If someone else comes up here saying that they have those glitches as well, I'll just call it a day and give for granted that there's some kind of limit by the hardware it runs on which produces those glitches.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 6:36 pm 


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These are minor programming errors due to oversight in the creation of the game. I'm sure they did a lot of testing in emulators and did not see them as a result.

The lines that flicker on the screen are because of palette writes mid-frame. This would likely not be too hard to fix in software, and I'm working on a patch for that (among other things). The correct way for this to be done is to defer these palette writes into a queue, which gets committed during the vertical retrace interval.

The boss getting corrupted rapidly, and the shop interface having white boxes, are both the same problem, and it is simply sprite overdraw. Too much sprite data for a given line, just like on an NES game. The System 16 sprite system reacts interestingly to having too much sprite data requested on one line. Rather than simply dropping further data, the result is that the remaining data for the sprite gets pushed down by one line, while the total sprite height remains the same. System 16 sprites are stored per-line, not per-tile, so data fetches are iterative. A dropped line doesn't increment the line index, hence the strange movement of the boss's face. This'd be a bit harder to fix, as it is a consequence of a design oversight. A hotfix could be to detect too many bomb explosion sprites being drawn at once, and to omit them in that situation.

None of this happens in emulation because the emulators are not accurate enough. Nothing is wrong with your PCB or ROMs.
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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 8:38 pm 


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Wow, my wild guess was actually correct :mrgreen:
Feels good.

And it feels even better knowing that nothing's wrong on my end, thanks mike!

It surely makes you wonder about the accuracy of the emulators we use... we give for granted that emus like MAME are *very* accurate, but it seems like there are corner cases which haven't been figured out yet.

One thing still intrigues me: it's known that the game has been shown in some test locations, running on a System16C board in an arcade cabinet. How come those guys didn't notice those glitches? They just didn't care? It would make sense since their target were obviously PS2 users, but still...

Oh well, I'll be waiting patiently for your patches, so my OCD can find peace :mrgreen:
About the boss glitch: it's definitely the bomb explosions, today I died in a very stupid way on that boss and I couldn't trigger that glitch with just a single bomb, no matter how close/fast I spammed bomb and shot together.
Limiting the bomb explosions in this situation would be a viable solution for sure.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 10:25 pm 


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donluca wrote:
It surely makes you wonder about the accuracy of the emulators we use... we give for granted that emus like MAME are *very* accurate, but it seems like there are corner cases which haven't been figured out yet.

Definitely not. I do believe MAME (at least nowadays) has some sort of code involving accuracy, but I can't imagine that necessarily implies implementing all kinds of limitations that rarely have an effect on the actual games.
When you described the glitches, my theory was the exact same that mikejmoffitt comfirms - timing issues regarding writes to the video ram. That is such a classic error you see on a lot of homebrew written entirely for emulators, as emulators don't really have any reason to restrict when you can or can't access certain parts of memory if no official games ever did that.

Genuinely accurate emulators are few and very far between.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 02, 2019 11:52 pm 


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To be truly accurate, you need transistor level emulation.

That's not coming any time soon.

In the meantime, what we have is pretty good. In most cases, you just want a hack thrown in to make you believe it's "accurate".
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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Jan 07, 2019 10:27 pm 


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Today I managed to trigger another glitch!

Spoiler: show
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All the sprites had vertical lines on them! Yay!

The sprites even retained the glitch between two levels, I had to go to the dark side and back to clear them up.

Looks like mike will have quite a bit of work cleaning up the code for it to work correctly on the System16C :P


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Jan 07, 2019 10:44 pm 


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I don't see how that could possibly be a software glitch. Sounds like your board could use a little attention. The lines are spaced every four pixels, and only affect certain colors. I bet it is an intermittent data connection to your sprite data ROMs.
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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Mon Jan 07, 2019 11:10 pm 


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I've been playing the board for weeks and this is the first time this happens and it went away as soon as I cycled to Dark side level and back.

From experience, issues like this are permanent if there's a fault in the board, they do not go away like that. This is why I'm thinking about a software bug.

I'll keep playing it until I've cleared it (got through the boss rush zone and to the last boss where I lost my last life, sad times) and see if anything similar happens again.

Just to rule out any possibilities: the board has always been inside the cab since I started playing it, the cab has not been moved or kicked or anything, so, from a physical point of view, there haven't been any kind of changes.

If this keep happening I'll definitely take a look at the board, but AFAIK the only thing which could have happened is an EPROM going bad, since no changes have happened.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Tue Jan 08, 2019 12:38 am 


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Well, I've cleared the game on both sides and 4-looped it, and have never seen it do that once, so I'm pretty sure you have an intermittent hardware thing going on :P
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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Tue Jan 08, 2019 12:14 pm 


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Good Lord, this game have 4 loops??? That's... disheartening, lol. I'll probably go for the first loop and call it a day. :P

I'll take out the board then and take a look, although I keep all my boards really clean, something might have gone over the EPROM pins and maybe shorted two address lines for a brief time, which was then retained into RAM until it was overwritten when I went to dark side and back.

I really hope it's not an EPROM going bad because I have only 1 more available.


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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 09, 2019 8:51 pm 


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It might have more, but I choked halfway through the last loop.
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 Post subject: Re: Calling all owners of Fantasy Zone II (System16C)
PostPosted: Wed Jan 09, 2019 9:37 pm 


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I have a suicidal tendency to get really close to the bosses to get max damage, which often ends up killing me.

I should just relax and play it safe.

By the way, yesterday had another shot at it and, surprisingly, it only happened in a couple of cases and for a fraction of second, like a single flash. So there's definitely something wrong, I need to check the EPROMs and make sure everything is nice and clean.


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