ICEknight, on 07 December 2011 - 10:51 AM, said:
Since Sonic 2 loads every object in the vertical column the screen is at, wouldn't using the Sonic 3 method of loading objects make things much faster?
Definitely, and it's the only way to make a busy level such as Metropolis even work at a decent rate. I think flamewing had to implement the Sonic 3 object manager because of the increased overhead of having three characters at the same time in Sonic 2 Heroes. But I'm pretty sure that in 2P mode, the game would still slow down when somebody loses all of their rings, gets invincibility, etc, regardless of whatever tricks you pull.
As for the original game and its odd pick of levels, it actually makes more sense when you think about the ones they left out:
- Chemical Plant has water (in Act 2, anyway), which is problematic due to the mid-scanline pallete switch trickery, as noted above.
- Aquatic Ruin has water too.
- Hill Top does a lot of crazy things with the background layer to simulate moving ground and lava.
- Oil Ocean... well, I can't think of anything but the oil at the bottom of the screen, which may very well be a non-issue.
- Metropolis is a vertically-wrapping level, which would likely require specific code to work correctly in 2P mode.
Emerald Hill, Casino Night and Mystic Cave aren't so much random picks as they are "safe" choices, with not much in the way of nonstandard level gimmicks.