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Background Scrolling Data Info

TODO:
- Verify info for BG start position nybble — 0x2 and 0x3 in particular.
- How specifically do "Disable vertical scrolling" and "Automatic horizontal scrolling" work? What all do bytes 13 and 16 do?
- Might be nice to list which BG speeds and such are all used.

Foregrounds and backgrounds scroll differently in many levels — sometimes they have a fast speed ratio and sometimes they can be completely static. This can be adjusted by hex editing your level.

  • Bottom background --> Change block 3.
  • Top background --> Change block 5.

NSMBe screenshot of the level hex editor open to block 5. The leftmost nybbles of byte 11 and 13 are labeled as "BG starting position" while the rightmost nybbles are labeled as "Speed".

  • Byte 11: Control BG horizontal scrolling.
  • Byte 13: Control BG vertical scrolling.

And for each byte:

  • First Nybble: Controls where the background starts relative to the view and how it loops. This seemingly does nothing for horizontal looping or start position.
  • Second Nybble: Controls scroll speed relative to stage foreground speed.

(Image source: MarioSunshine)

Start position and loop data
  • 0x0: Starts from bottom of view offset by 32px; loops entire background.
  • 0x1: Starts from top of view offset by 32px; loops entire background.
  • 0x2: Duplicate of 0x0?
  • 0x3: Duplicate of 0x1?
  • 0x4: Starts from bottom of view offset by 32px; loops top half of background.
  • 0x5: Starts from top of view offset by 32px; loops bottom half of background.

Any value higher than 0x5 freezes the game.

Scroll speed data

Table address in overlay 0: 0x0002F468
Table address in memory: 0x020C7B48

  • 0x0: Same as FG speed. Used in w2-3 (sewer level) for example.
  • 0x1: 50% FG speed.
  • 0x2: 25% FG speed. Common for top backgrounds.
  • 0x3: 12.5% FG speed. Common for bottom backgrounds.
  • 0x4: 120% FG speed. Unused.
  • 0x5: 75% FG speed.
  • 0x6: 6.25% FG speed.
  • 0x7: 9.375% FG speed.
  • 0x8: 20.3125% FG speed.
  • 0x9: Same as FG speed.
  • 0xA: Same as FG speed.
  • 0xB: Same as FG speed.
  • 0xC: Same as FG speed.
  • 0xD: 200% FG speed. Unused.
  • 0xE: 400% FG speed. Unused.
  • 0xF: 800% FG speed. Unused.

(Source: RoadrunnerWMC)

Disabling vertical scrolling

  • Bottom background --> Change both bytes 13 and 16 of block 3.
  • Top background --> Change both bytes 13 and 16 of block 5.
  • Byte 13: set to 0x40.
  • Byte 16: set to 0x10.

(Source: MeroMero)

Automatic horizontal scrolling

Works for any background that already has parallax scrolling. This can be achieved by putting a value of 0x10 for byte 16 and it will scroll the whole background instead of only some of it.
(Note: if byte 13 value is somewhere between 0x40 and 0x4F, this effect will be overridden and instead the vertical scrolling will be disabled).
(Source: MeroMero)
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