Moving this here from the development subforum since I guess it will be of interest for non-contributors too:
Macaw escribió:Just messing around here a bit. These are some direct screen captures using the emulator. They end up as 640x400, and I've taken one both with and without m88's scanline option. I still have no idea how stuff really should look on a real pc88, so I'll let you analyze it a bit. I'll mess around with m88's options more over time.
In the low res screenshots thread you also mention how some games such as Tritorn 2 were designed with fake scanlines. Are you sure you weren't just fooled by the m88 scanline option? In the first shot of Dios here with the m88 scanline option off you can see that there are no lines at all, though perhaps Dios wasn't designed with fake scanlines?
Perhaps I've completely misunderstood you in the first place, I still don't know much of the technicalities in this area but would appreciate learning more.

Old-computer screenshots is indeed quite a tricky subject. Most of them from 1983 onwards--PC88 included--supported both, 15 kHz (low res) and 31 kHz (hi res) modes. For PC88 and PC98, almost always you'd find either, 640 x 200 or 640 x 400 (they were actually 640 x 240 and 640 x 480 once the monitors' benchmarks were set as I explained earlier, but let's just leave that apart for now). PC88's hi-res mode was pretty limited color-wise, so we must assume most games used 640 x 200. So an actual frame-buffer screen from your game should be like this:

By that (which I guess it's the first PC88 screen ever at its original resolution [laughs]), you can understand why the emulator--conceived, sadly, only for stardard PC video cards--automatically line-doubles the image (1st screen in your post) -- the aspect ratio through a standard PC is way too distorted. The game, you know, despite the resolution, had a 4 : 3 aspect ratio (not really 4 : 3 if we count the excluded borders, but close enough). It could be possible--I never had a PC88--that the game was line-doubled on the original frame-buffer for a 'fake' hi-res display so that the emulator is actually mimicking that behaviour, but given that there also existed 15 kHz-only PC88 monitors, I don't find that too plausible. That's also the reason for a universal scanlines simulation feature on the emulator (your 2nd screen) -- it's the most natural way to replicate the original low-res display on hi-res video hardware (therefore rendering the line-double method quite useless), though we've already explained that the final result here--no matter the type of monitor you're using--lacks the beauty of actual 'scanlines' for several reasons (hence the point I've been claiming for years of never using a standard PC for proper emulaton, if you're really into that).
Now PC98 is a bit different. It was especially designed for hi-res (most of its monitors indeed couldn't do 15 kHz) and we must assume that most games were rendered at 640 x 400. This was a problem for simultaneous PC88/PC98 releases or PC88 - PC98 ports -- you now needed to double the original lines for a hi-res display, and that's what many devs did:

PC98 Xak

PC98 Fray
(They didn't need any excuse though -- many original PC98 games were also designed at half the display resolution, saving RAM demands and well, effort.)
Fortunately others decided against this awful method and invented the scanlines simulation -- instead of drawing the same line twice, even lines would be black lines. That PC98 Tritorn II screenshot you mention, to answer your question, doesn't have scanlines added by the emulator; the game was rendered exactly like that. You can check these other examples for more color:

PC98 Lessern Mern

PC98 Vain Dream II
Notice the scanlines are applied only on the action area or the background -- there's no way an emulator could do that. Of course they went even further and invented different patterns which, applied on the line-doubled picture, would alleviate the issues of design - display discrepancies:

PC98 Digan no Maseki
So that's why you won't find (my guess) a scanlines simulation feature on any PC98 emulator.
This pretty much covers, not just your questions, but the whole core of what was going to be part 2 of the Scanlines -- Ab Initio article, so it's now done for anyone's interested. Thank Macaw. The only remaining thing would be illustrating with actual photographs the wonders of 15-kHz RGB CRTs to let everybody see what they've missed, and that will come with the new Site's content itself. So yeah.
Edit: Grammar bits.