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Sprite set file: Difference between revisions
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<syntaxhighlight lang="c"> | <syntaxhighlight lang="c"> | ||
struct spriteset_header { | struct spriteset_header { | ||
u16 | u16 palStart; // palette start index in the sprite palettes file | ||
u16 spriteCount; // number of sprites in this sprite set | u16 spriteCount; // number of sprites in this sprite set | ||
u16 unknown_0x04; | u16 unknown_0x04; | ||
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struct spriteset_obj { | struct spriteset_obj { | ||
u8 flip; // bitmask; 4 = horizontal, 8 = vertical | u8 flip; // bitmask; 4 = horizontal, 8 = vertical. TODO: other bits? | ||
// 00=8x8, 01=16x8, 02=8x16 | // 00=8x8, 01=16x8, 02=8x16 | ||
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// Bottom 12 bits: Start index for this OBJ in the raw tile data array | // Bottom 12 bits: Start index for this OBJ in the raw tile data array | ||
// Top 4 bits: Palette index | // Top 4 bits: Palette index, add to spriteset_header.palStart | ||
u16 tileAndPalette; | u16 tileAndPalette; | ||
}; | }; | ||
struct spriteset_tile { | struct spriteset_tile { | ||
u8[32] | u8 data[32]; // Raw GBA tile data (8x8 px, 4bpp) | ||
} | }; | ||
</syntaxhighlight> | </syntaxhighlight> | ||
= Palettes = | |||
Each OBJ is linked to the palette it should use using the information in spriteset_obj.tileAndPalette and spriteset_header.palStart. However, the game engine can override this (used e.g. to animate menu cursors etc.). | |||
Each game's master file table contains a single file that defines ''all'' palettes for each spriteset_sprite. This file is stored in the MFT directory with id_low = 0x4679 and id_high = 0x9a65. This directory will only contain a single file with the ID 0xc5e9 in every game. | |||
The structure of this file is simple: A 4 byte header, containing the number of palettes in this file, followed by an array of that many palettes. Each palette is 0x20 bytes in size (16 entries per palette, 2 bytes per entry, see [https://problemkaputt.de/gbatek-lcd-color-palettes.htm GBATEK]). The game engine will automatically copy palettes from this file into palette RAM as neccessary. | |||
To get the palette index for a spriteset_obj, add <code>(spriteset_obj.tileAndPalette >> 12) + spriteset_header.palStart</code>. | |||
= Usage example = | = Usage example = | ||
<syntaxhighlight lang="c"> | <syntaxhighlight lang="c"> | ||
void load_sprite(spriteset_header* spriteset, int spriteId) | void load_sprite(spriteset_header* spriteset, void* spritePalettes, int spriteId) | ||
{ | { | ||
// spriteset should point to the start of a spriteset file | |||
// spritePalettes should point to the start of the sprite palettes file (there is only one per game) | |||
spriteset_sprite* sprites = (u8*)spriteset + spriteset->offsetToSprites; | spriteset_sprite* sprites = (u8*)spriteset + spriteset->offsetToSprites; | ||
spriteset_tile* tiles = (u8*)spriteset + spriteset->offsetToTiles; | spriteset_tile* tiles = (u8*)spriteset + spriteset->offsetToTiles; | ||
spriteset_sprite* sprite = &sprites[spriteId]; | spriteset_sprite* sprite = &sprites[spriteId]; | ||
// do something with sprite | // do something with sprite | ||
spriteset_obj* objs = (u8*)spriteset + spriteset->offsetToOBJs + sprite->objOffset; | |||
for (int objIndex=0; objIndex < sprite->objCount; objIndex++) { | for (int objIndex=0; objIndex < sprite->objCount; objIndex++) { | ||
spriteset_obj* obj = objs | spriteset_obj* obj = &objs[objIndex]; | ||
// do something with obj | // do something with obj | ||
int | int firstTileIndex = obj->tileAndPalette & 0xfff; | ||
spriteset_tile* firstTile = &tiles[ | spriteset_tile* firstTile = &tiles[firstTileIndex]; | ||
// do something with the tiles | |||
// number of tiles is implied by sprite->shape | // number of tiles is implied by sprite->shape | ||
// | // for OBJs with a height of more than 1 tile, successive rows of tiles are stored 16 tiles apart. | ||
// example: assuming startTileIndex = 4 and shape = 8x16: tile indices are 4 and 20. | |||
// color lookup example: | |||
int pixelColor = firstTile->data[0] & 0xf; // extract color of 1st pixel in the tile | |||
int paletteIndex = spriteset->palStart + (obj->tileAndPalette >> 12); | |||
// First 4 bytes are an ignoreable header, and each palette is 0x20 bytes in size (16 colors * 2 bytes per color) | |||
u16* palettePtr = (u8*)spritePalettes + 4 + 0x20*paletteIndex; | |||
u16 paletteEntry = palettePtr[pixelColor]; | |||
} | } | ||
} | } | ||