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01_hardware/ocs_a500/sprites.md
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@ -13,9 +13,9 @@ The OCS/ECS chipset provides **8 hardware sprites**, each 16 pixels wide and arb
| Count | 8 sprites |
| Width | 16 pixels fixed |
| Height | Programmable (any number of lines) |
| Colours | 3 (+1 transparent) per sprite |
| Colour source | Sprite colour registers (COLOR16–COLOR31) |
| Attach mode | Pairs 0/1, 2/3, 4/5, 6/7 → 15 colours |
| Colors | 3 (+1 transparent) per sprite |
| Color source | Sprite color registers (COLOR16–COLOR31) |
| Attach mode | Pairs 0/1, 2/3, 4/5, 6/7 → 15 colors |
## Sprite Registers
@ -60,14 +60,14 @@ Each line of the sprite consists of two 16-bit words (DATA and DATB) fetched fro
```
For each scanline of sprite:
Word 1 (DATA): bit 15..0 → pixel bit 1 (colour bit 1)
Word 2 (DATB): bit 15..0 → pixel bit 0 (colour bit 0)
Word 1 (DATA): bit 15..0 → pixel bit 1 (color bit 1)
Word 2 (DATB): bit 15..0 → pixel bit 0 (color bit 0)
Pixel colour:
Pixel color:
DATA[bit] = 0, DATB[bit] = 0 → transparent
DATA[bit] = 0, DATB[bit] = 1 → colour 1 (COLOR17 for sprite 0)
DATA[bit] = 1, DATB[bit] = 0 → colour 2 (COLOR18)
DATA[bit] = 1, DATB[bit] = 1 → colour 3 (COLOR19)
DATA[bit] = 0, DATB[bit] = 1 → color 1 (COLOR17 for sprite 0)
DATA[bit] = 1, DATB[bit] = 0 → color 2 (COLOR18)
DATA[bit] = 1, DATB[bit] = 1 → color 3 (COLOR19)
```
## Sprite Data in Memory
@ -85,29 +85,29 @@ Agnus DMA reads the sprite from a memory block structured as:
Word: $0000 (SPRnCTL = 0)
```
## Colour Mapping
## Color Mapping
Sprites share colour registers with bitplanes:
Sprites share color registers with bitplanes:
| Sprites | Colour Registers |
| Sprites | Color Registers |
|---|---|
| 0 and 1 | COLOR16–COLOR19 |
| 2 and 3 | COLOR20–COLOR23 |
| 4 and 5 | COLOR24–COLOR27 |
| 6 and 7 | COLOR28–COLOR31 |
COLOR16 (the first colour of sprite pair 0/1) is always transparent — the sprite background. Only COLOR17–COLOR19 are visible for sprites 0/1.
COLOR16 (the first color of sprite pair 0/1) is always transparent — the sprite background. Only COLOR17–COLOR19 are visible for sprites 0/1.
## Attached Sprites (15 Colours)
## Attached Sprites (15 Colors)
Pairing two sprites (`ATT` bit in SPRnCTL of the even sprite) combines their DATA/DATB bits to produce a 4-bit colour index (16 colours, one transparent):
Pairing two sprites (`ATT` bit in SPRnCTL of the even sprite) combines their DATA/DATB bits to produce a 4-bit color index (16 colors, one transparent):
```
4-bit colour = {SPR_even.DATA[bit], SPR_even.DATB[bit],
4-bit color = {SPR_even.DATA[bit], SPR_even.DATB[bit],
SPR_odd.DATA[bit], SPR_odd.DATB[bit]}
```
This gives 15 visible colours per pair, using COLOR16–COLOR31 for pair 0/1.
This gives 15 visible colors per pair, using COLOR16–COLOR31 for pair 0/1.
## BPLCON2 — Sprite Priority
@ -122,7 +122,7 @@ Default: sprites appear in front of all bitplanes.
## OS Mouse Pointer
AmigaOS's Intuition uses sprite 0 (and 1 in attached mode for colour pointer) for the mouse pointer. Intuition calls `SetPointer()` / `ClearPointer()` on a Window to install custom pointer sprites.
AmigaOS's Intuition uses sprite 0 (and 1 in attached mode for color pointer) for the mouse pointer. Intuition calls `SetPointer()` / `ClearPointer()` on a Window to install custom pointer sprites.
```c
SetPointer(window, pointer_data, height, width, x_offset, y_offset);