What sorts of limitations are there on moving backgrounds?

[pwnagekirby]

So a couple follow-ups:

For MMC5's right-left splits, does both sides needing to have the same fine X basically mean that out of these four examples, only the first one is possible? And also, is there a limit to the number of right-left splits that can be active at the same time?

And also, for Batman: Return of the Joker, I always figured the clouds were just from a scrolling split background. But then there's this scene, where there's a background(?) element in front of the clouds. Can this be done purely with scrolling backgrounds, or is there something else going on here?

[lidnariq]

For MMC5's right-left splits, does both sides needing to have the same fine X basically mean that out of these four examples, only the first one is possible?

#3 is actually possible too.

And also, is there a limit to the number of right-left splits that can be active at the same time?

On any given scanline, you can only have two.

There's one nametable that's dedicated to just the contents of the splits, and it has no coarse X scroll at all. So you'll have to juggle data to match.

And also, for Batman: Return of the Joker, I always figured the clouds were just from a scrolling split background.

That's actually tile bankswitching animation. Try loading the game in an emulator with a debugger and look at the pattern tables:

[tokumaru]

For MMC5's right-left splits, does both sides needing to have the same fine X basically mean that out of these four examples, only the first one is possible?

I'm not an MMC5 expert by any means, but I think the 3rd example should be possible too, if you disable the vertical split mid-screen.

And also, is there a limit to the number of right-left splits that can be active at the same time?

Apparently you only get one split.

This feature is so awkward... it has so many restrictions that it's hard to think of a good use case for it during actual gameplay. I generally avoid relying on any of the MMC5's features, since that mapper is still pretty rare and not readily available for use in homebrew releases. AFAIK it hasn't even been fully reverse-engineered yet.

And also, for Batman: Return of the Joker, I always figured the clouds were just from a scrolling split background. But then there's this scene, where there's a background(?) element in front of the clouds. Can this be done purely with scrolling backgrounds, or is there something else going on here?

Those are animated background patterns. There's no screen scrolling at all involved in that effect, the game is just switching between rotated versions of the cloud graphics in order to make it look like they're moving. Sword Master and Metal Storm are two other games that make heavy use of that effect to create multiple overlapping scrolling planes.

EDIT: Oops! Too late!