Sky

The sky is a quad the size of the screen drawn at the beginning of each frame, using different colours for the top and bottom to create a gradient. The table of colours is at 0x1220E0 in ROM, and has one entry per track:

struct mk64_sky_color {
  uint16_t top_r, top_g, top_b;
  uint16_t bottom_r, bottom_g, bottom_b;
};

Although these are 16-bit values, only the lower 8 bits seem to be used. It's not known what the upper 8 bits are used for; they aren't always zero.

These values don't seem to have any effect in Choco Mountain and Banshee Boardwalk, possibly because of fog blocking the sky. The clouds, stars etc are most likely drawn by hardcoded display lists.

Sky Color Data

Sky color table from US ROM:

Track	Top R	Top G	Top B	Bot R	Bot G	Bot B
0x00 Mario Raceway	00 80	10 B8	17 F8	00 D8	1B E8	7D F8
0x01 Choco Mountain	00 FF	00 FF	00 FF	00 FF	00 FF	00 FF
0x02 Bowser's Castle	00 30	06 08	C1 78	00 00	00 00	00 00
0x03 Banshee Boardwalk	00 00	00 00	00 00	00 00	00 00	00 00
0x04 Yoshi Valley	00 71	00 46	00 FF	00 FF	00 B8	00 63
0x05 Frappe Snowland	00 1C	00 0B	00 5A	00 00	00 63	00 A4
0x06 Koopa Troopa Beach	00 30	06 98	D3 78	00 D8	1B E8	7D F8
0x07 Royal Raceway	00 EE	00 90	00 FF	00 FF	00 E0	00 F0
0x08 Luigi Raceway	00 80	10 B8	17 F8	00 D8	1B E8	7D F8
0x09 Moo Moo Farm	00 00	00 12	00 FF	00 C5	00 D3	00 FF
0x0A Toad's Turnpike	00 00	00 02	00 5E	00 D1	00 41	00 17
0x0B Kalimari Desert	00 C3	00 E7	00 FF	00 FF	00 C0	00 00
0x0C Sherbet Land	00 80	10 B8	17 F8	00 D8	1B E8	7D F8
0x0D Rainbow Road	00 00	00 00	00 00	00 00	00 00	00 00
0x0E Wario Stadium	00 14	00 1E	00 38	00 28	00 3C	00 6E
0x0F Block Fort	00 80	10 B8	17 F8	00 D8	1B E8	7D F8
0x10 Skyscraper	00 00	00 00	00 00	00 00	00 00	00 00
0x11 Double Deck	00 71	00 46	00 FF	00 FF	00 B8	00 63
0x12 DK's Jungle Parkway	00 FF	00 AE	00 00	00 FF	00 E5	00 7C
0x13 Big Donut	00 00	00 00	00 00	00 00	00 00	00 00
0x14 Award Ceremony	00 EE	00 90	00 FF	00 FF	00 E0	00 F0