Why does Ys III feature an interlaced video mode?

Valis III had the same thing. Maybe it selectively applies a higher resolution to the text boxes to make the characters clearer, which is more important in Japanese? I can't imagine it makes the whole game actually render at a higher resolution.

 

It's probably not a case of the TV not being able to properly display text in 240p, but rather it's just a nice QoL feature to have a higher detailed font for readability, since in 480i mode the resolution gets doubled vertically.

 

Should probably mention before everyone gets confused, this is not interlaced mode 2 like Sonic 2, where the resolution is doubled by drawing odd and even 8x16 pixel tiles on odd/even frames. This is interlaced mode 1, the tile format is the same, it's using identical pixel rows just on odd/even frames.

 

I have no idea.



Most emulators don't support the mode (properly) - BlastEm will, but as said, you don't higher resolution text, it's literally just drawing every other line per frame.

I can only assume it's a performance thing, because it's certainly not a visual one. Maybe it reduces slowdown in certain areas? Is that even much of a thing with this style of RPG?

 

Maybe it was intended for people playing on RGB monitors? When I output 240p content to my Sony PVM, you can see the scanlines clearly on the monitor, but when I run anything with an interlaced video mode, the characters appear full height owing to the field offset. Even without the increased resolution of the sonic 2 interlaced mode, the mask gaps in kanji would make reading them harder on such a monitor because there actually are bits where single-pixel gaps in a stroke can drastically change the reading when kanji are so low resolution. In other words, with the scanline gaps, you might get confused if there is actually supposed to be a gap in the stroke behind the scanline or not since it'll always look broken up. Context would obviously help you understand but a clearer picture would be better.

also with a flicker fixer, the interlaced image would hold steady. Flicker Fixers weren't too common in the US, but they were common in parts of the world where they'd use RGB monitors. My Amiga has a flicker fixer for high resolution interfaced mode, for example.

EDIT: Just noticed something worth mentioning: Ys III was originally made for the PC 8801, which had two video modes, a 640x200 8-color mode, and a 640x400 2-color interlaced mode. Well check out these screenshots in-game from the original version:



It looks like Ys in the original version could somehow switch the video mode mid scanline or something? The main game is 640x200 mode, but the text boxes are 640x400 interlaced mode it seems. No scanlines between the text, but scanlines everywhere else, and clearly using more than 2 colors.

Read up further about it, I think this is where it comes from. The PC-8801 renders graphics in two stages with independent resolutions. The first pass renders graphics, and Ys III uses the 640x200 8-color mode for this, then the second pass renders only text, and it's rendering at 640x400 interlaced 2 color mode.

Valis does the same thing on the PC-8801. I'm wondering if this is a quirk left over from those original games.

 

Given that interlace mode 2 would require custom graphics, and would corrupt everything on-screen that isn't in the appropriate format (see Sonic 2's non-2P levels in 2-player mode), no, it isn't using the wrong interlace mode. And since the feature literally just causes the screen to jitter up and down every frame, it isn't incorrect emulation either.

It's not that: Interlace Mode 1 has no performance impact whatsoever.

Cooljerk's explanation makes the most sense to me.