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Routines |
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Used by the routine at CheckTerrainCollision.
Sets up CheckTerrainCollision: keeps the size of the object in SegmentColumn and clears the working values, finds where the object will be after it has moved by its speeds using FindHorizontalMove and FindVerticalMove, and keeps its speeds. Carries on at FindTilesOverlapped.
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| StartTerrainCheck | 48783 | LD (52803),BC | Update the segment column. | |||||||
| 48787 | XOR A | Clear A. | ||||||||
| 48788 | LD (23594),A | The object does not reach the next column. | ||||||||
| 48791 | LD (23595),A | The object does not reach the zone above. | ||||||||
| 48794 | LD (23581),A | Update the tiles still to test. | ||||||||
| 48797 | LD (23605),A | Update the collision status. | ||||||||
| 48800 | LD (58395),A | Update the slope direction. | ||||||||
| 48803 | CALL FindHorizontalMove | Call FindHorizontalMove. | ||||||||
| 48806 | LD (49023),HL | Update the tile position. | ||||||||
| 48809 | LD (23598),HL | Update the piece column. | ||||||||
| 48812 | CALL FindVerticalMove | Call FindVerticalMove. | ||||||||
| 48815 | LD (49025),HL | The vertical position after the move. | ||||||||
| 48818 | LD (23600),HL | Update the back to front flag. | ||||||||
| 48821 | LD A,(23589) | The collision mode. | ||||||||
| 48824 | INC A | Advance A. | ||||||||
| 48825 | JR Z,StartTerrainCheck_Ship | Jump to StartTerrainCheck_Ship if the zero flag is set. | ||||||||
| 48827 | DEC A | Step A back. | ||||||||
| 48828 | CALL Z,ReverseObjectSpeed | Call ReverseObjectSpeed if the zero flag is set. | ||||||||
| 48831 | JR StartTerrainCheck_Speeds | Jump to StartTerrainCheck_Speeds. | ||||||||
| StartTerrainCheck_Ship | 48833 | LD HL,(51454) | Fetch the word at 51454 into HL. | |||||||
| 48836 | LD (51436),HL | Update the high byte of the ship's horizontal speed. | ||||||||
| 48839 | LD HL,(51456) | Fetch the word at 51456 into HL. | ||||||||
| 48842 | LD (51438),HL | Update the high byte of the ship's vertical speed. | ||||||||
| StartTerrainCheck_Speeds | 48845 | LD A,(IX+7) | Read offset 7 of IX. | |||||||
| 48848 | LD (48781),A | Update the saved horizontal speed. | ||||||||
| 48851 | LD A,(IX+9) | Read offset 9 of IX. | ||||||||
| 48854 | NEG | Negate A. | ||||||||
| 48856 | LD (48782),A | Update the saved vertical speed. | ||||||||
| 48859 | LD A,(52803) | The segment column. | ||||||||
| 48862 | LD (23596),A | Update the segment screen column. | ||||||||
| 48865 | LD A,(52804) | The segment row. | ||||||||
| 48868 | LD (23597),A | Update the segment screen row. | ||||||||
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Continue on to FindTilesOverlapped.
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| Prev: 48707 | Up: Map | Next: 48871 |