3 is blue

anyway

I randomly got some interest in this again, and wondered if I could get this working in a production level

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for reference: https://nsmbhd.net/thread/3157-multibg-ii-the-return/

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what we know so far:

* unused level 3 uses this
* it's broken af
* structure for BG info block was somewhat different at the time

VRAM layout:
0x06000000: Jyotyu tileset
0x06003000: level tileset
0x0600A000: end-castle tileset
0x0600C000: top BG tileset
0x06011000: bottom BG tileset
0x06018000: BG2 tilemap (FG)
0x0601A000: BG3 (top BG)
0x0601C000: BG1 (bottom BG)
0x0601E000: empty (space for the extra crap to land, apparently)

now for pure speculation

* secondary background tilemap would have been loaded at 0x0601E000. this would have allowed a simple, one-layer background (prolly sufficient for a small sub-area like in the unused level).

* not clear where the tileset for said BG layer would have been loaded. maybe the different BG layers shared a same tileset.

* the level tileset for the sub-area would have been loaded at 0x0600A000, where the end castle is loaded.

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the code

* the tilemap address for the BG layers is set based on which BG info block is active. 0x0601A000/0x0601C000 if the ID is 0 or 3, 0x0601E000 otherwise.

* prior to that, the tilemaps are loaded -- the code goes through each BG info block and loads the associated tilemap. the issue is that they all get loaded at the same VRAM address (which is inferred from the current BGxCNT setting).

* have not yet looked into level tilesets.
_________________________
Kuribo64 - RH-fucking-cafe - Kafuka

zrghij

I'll post some info and wild speculation... nothing too new.

comparing the layouts of various level header blocks against a pretty normal level, 1-2.





so obviously, our unused level has two entries in block2 and block3.

view parameters (unk1/unk2/unk3) determine which one to use (tho not all places use it).

but also: block0 clearly has multiple tilesets defined for bottomBG and FG. the structure implies that each layer could have up to 3 tilesets loaded, although it's unclear how it would work and what the VRAM layout would be. possible it was limited in ways -- unused3 has no top BG defined.

we observe a similar oddity in block2 and block3: in each, the second entry has the palette ID set to FFFF, which would skip loading a palette entirely. however, the next u16 is set to 0003, which suggests that there were more palette slots available (probably up to 3, too).

then we also see something in the MSB of the tilemap ID: they are set to 0300 and 0403. the game code ignores the MSB. not sure what this is all about.

this implies that the various BG layers involved would have to be made to work with a given VRAM layout in mind, or that there would be code for fixing tilemap entries as needed when loading graphics.

there is code for setting the tilemap base address for BG layers based on which BG block is in use, but it doesn't set the tileset base address.

I'm digging a bit in the code to see if I can find remnants of this multiBG stuff, because it's interesting. but there isn't a lot. the code for loading tilesets and palettes only loads the first entry. the code for loading tilemaps can load multiple, but they're all loaded to the same address, which defeats the point.
_________________________
Kuribo64 - RH-fucking-cafe - Kafuka

zrghij

it's the latter - unused level 3 uses it

a different view could have a different tileset and background set

it seems it was limited but interesting regardless
_________________________
Kuribo64 - RH-fucking-cafe - Kafuka

zrghij

was digging through old shit, and

https://nsmbhd.net/thread/991-multibackground-experiments/#14314

looked at level 3-A and I do notice that the tileset values are: 0030 0000 FFFF

same goes for the palette entries in block 4: 0030 0000 FFFF

I guess that's one oddity, but that level's palette stuff is unrelated to the multiBG stuff I think

the game just knows that the tileset's palette file is bigger
_________________________
Kuribo64 - RH-fucking-cafe - Kafuka

zrghij

o!

yeah... I think I haven't seen any code even use those values.
_________________________
Kuribo64 - RH-fucking-cafe - Kafuka

zrghij