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Routines |
| Prev: C501 | Up: Map | Next: C5B5 |
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Room scenery elements' co-ordinates need to be tweaked with an offset amount based on Maroc's room entry point.
This routine adjusts each element's horizontal and vertical positions of each of the room item data sets at 7C00 and the foreground scenery object sets at 7F01.
Calculate offset based on Maroc's default room position and his room entry point
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| C571 | LD A,($EB75) | Maroc's horizontal (entry) position when he moves to a new room, in half-character/4-pixel steps | ||
| C574 | LD C,A | |||
| C575 | LD A,($EAC0) | Maroc's default horizontal (X-axis) room position (in half-characters = 29) | ||
| C578 | SUB C | Offset amount = Maroc's default horizontal room position (~ 14.5 character spaces) minus his horizontal entry position | ||
| C579 | LD B,A | ...store in B register | ||
| C57A | LD A,($EB76) | Maroc's vertical (entry) position when he moves to a new room, in pixels | ||
| C57D | LD C,A | |||
| C57E | LD A,($EB74) | Maroc's default vertical (Y-axis) room position (in pixels) | ||
| C581 | SUB C | Offset amount = Maroc's default vertical room position (~ 48 pixels) minus his vertical entry position | ||
| C582 | LD C,A | |||
| C583 | LD D,$00 | Clear D register ready for DE offset addition shortly | ||
| C585 | LD HL,($DAEE) | Address pointer to room item data sets at 7C00 | ||
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Add co-ordinate offsets into bytes 6 (horizontal co-ordinate) and 8 (vertical co-ordinate) of each of the room item data sets at 7C00
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| C588 | LD A,(HL) | |||
| C589 | CP $FF | Skip next bit if no more data sets | ||
| C58B | JR Z,$C59D | |||
| C58D | LD E,$05 | DE contains offset to move along 5 bytes to 6th byte of set | ||
| C58F | ADD HL,DE | |||
| C590 | LD A,(HL) | Get item's horizontal room position (4-pixel/half-character steps) | ||
| C591 | ADD A,B | Add (or subtract if negative) the horizontal offset | ||
| C592 | LD (HL),A | ...and re-store | ||
| C593 | INC HL | Move along two bytes | ||
| C594 | INC HL | |||
| C595 | LD A,(HL) | Get item's vertical room position (in pixels) | ||
| C596 | ADD A,C | Add (or subtract if negative) the vertical offset | ||
| C597 | LD (HL),A | ...and re-store | ||
| C598 | LD E,$09 | Move along 9 bytes - this puts the pointer at the start of the next bank of data | ||
| C59A | ADD HL,DE | |||
| C59B | JR $C588 | Repeat until all data sets adjusted | ||
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Next do the same for the foreground scenery items, which are stored separately at 7F01
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| C59D | LD HL,($EB70) | Get address pointer to foreground scenery data sets at 7F01 | ||
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Update data item loop:
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| C5A0 | LD A,(HL) | |||
| C5A1 | CP $FF | Check first byte for end-of-data byte | ||
| C5A3 | JP Z,$C63B | Skip out of routine if found - all sets dealt with | ||
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Update co-ordinates at bytes 3 (horizontal) and 5 (vertical) of data set
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| C5A6 | INC HL | Move to byte 3 - horizontal co-ordinate | ||
| C5A7 | INC HL | |||
| C5A8 | LD A,(HL) | |||
| C5A9 | ADD A,B | Add (or subtract if negative) horizontal co-ordinate offset | ||
| C5AA | LD (HL),A | ...and re-store | ||
| C5AB | INC HL | Move to byte 5 - vertical co-ordinate | ||
| C5AC | INC HL | |||
| C5AD | LD A,(HL) | |||
| C5AE | ADD A,C | Add (or subtract if negative) vertical co-ordinate offset | ||
| C5AF | LD (HL),A | ...and re-store | ||
| C5B0 | INC HL | Move along three bytes to the next data set | ||
| C5B1 | INC HL | |||
| C5B2 | INC HL | |||
| C5B3 | JR $C5A0 | ...and repeat until all sets have been adjusted. | ||
| Prev: C501 | Up: Map | Next: C5B5 |