Shmups without diagonal level motion

[louisg]

I was playing Darius II and realizing that the levels move horizontally, vertically, but not both at the same time. Another game I noticed this with, most of the time, was Gate of Thunder (I think there's a short part though in st5 that moves diagonally?). This makes me think that the level format is composed of strips of tiles ala Metroid or Kid Icarus. Transitioning between the two axes of motion might even require a sort of scripted "teleport" in the level.

Why could this be? Allowing diagonal movement means that a lot of the tile data might be blank, and might require compression to get the stage down to a reasonable filesize.

What do you think? What are some ideas for storing 2d tiled levels with complex motion on a system with limited resources? And what are some other shmups which seem to follow this restriction?

[Drum]

Blood Money does what you're describing mid-level, and it's pretty herky-jerky about it (especially on a PC which wasn't up to it, as was my experience as a child) so there may be something to it. On the other hand, Vanguard has diagonally scrolling sections back in '81 so idk. Jump Bug -also '81 - made an early attempt at non-forced multi-directional scrolling in the pyramid stage, but it seems to have a tough time of it as it only scrolls on the x & y axes and not diagonally.

[Ex-Cyber]

AFAIK it's not really the tile data itself, but the size and organization of the name/attribute tables in VRAM (assuming a tile-based system with hardware scrolling). NES in particular only has enough VRAM for 2 screens, hence if you scroll in one direction you get the "next" screen, while if you scroll in the other direction you just wrap around the current screen. There are various tricks depending on the hardware, but typically for convenient diagonal scrolling you need enough VRAM for 4 screens' worth of tables. On NES, this could be expanded in the cartridge.

[S20-TBL]

Another game I noticed this with, most of the time, was Gate of Thunder (I think there's a short part though in st5 that moves diagonally?).

Funny you should mention Gate, Lords of Thunder had several diagonally-scrolling sections in Llamarada, Bosque, Dezant and Auzal (IIRC all of its levels had diagonally-scrolling sections, some longer than others, but these four have the longest and most evident ones). Of those four Dezant and Auzal were the ones that involved tiled foreground sections of the level being displayed, but to coincide with Ex-Cyber's statement they were generally no more than maybe 4-6 screens and somewhat uncluttered. Perhaps by this point they may have learned to optimize the hardware usage.

[louisg]

AFAIK it's not really the tile data itself, but the size and organization of the name/attribute tables in VRAM (assuming a tile-based system with hardware scrolling). NES in particular only has enough VRAM for 2 screens, hence if you scroll in one direction you get the "next" screen, while if you scroll in the other direction you just wrap around the current screen. There are various tricks depending on the hardware, but typically for convenient diagonal scrolling you need enough VRAM for 4 screens' worth of tables. On NES, this could be expanded in the cartridge.

Hmm that's a good point, but I'd still argue that even on hardware that supports diagonal scrolling easily, it would still complicate the level data. I guess at that point you'd either just RLE it or mark huge sections as "unused" somehow.