|
Routines |
| Prev: 56383 | Up: Map | Next: 56673 |
|
Used by the routine at TestGroupObjects.
Moves an entity off the overlap whose axis is the smallest of the three held at OverlapDistances. The x axis is handled by HandleOverlapFirst and the y axis by HandleOverlapSecond. On z, a player under a flagged block changes frame, the difference is planted for TestEntityCells, and the vertical speed pushes the entity clear. A saucer sets the high byte of its vertical speed to 2 first.
|
||||||||||
|
The smallest overlap chooses the axis. A saucer is pushed up before the choice is made.
|
||||||||||
| HandleOverlap | 56426 | LD A,(IX+0) | A saucer sets its vertical speed. | |||||||
| 56429 | CP 9 | |||||||||
| 56431 | JR NZ,HandleOverlap_Compare | |||||||||
| 56433 | LD (IX+18),2 | Set the high byte of the vertical speed to 2. | ||||||||
|
This entry point is used by the routine at TestEntityPair.
|
||||||||||
| HandleOverlap_Compare | 56437 | LD A,(56783) | Read the x overlap. | |||||||
| 56440 | LD B,A | |||||||||
| 56441 | LD A,(56785) | Compare it with the y overlap. | ||||||||
| 56444 | CP B | |||||||||
| 56445 | JP NC,HandleOverlapFirst | Handle x when it is the smaller overlap. | ||||||||
| 56448 | LD B,A | Keep the y overlap. | ||||||||
| 56449 | LD A,(56787) | Compare it with the z overlap. | ||||||||
| 56452 | CP B | |||||||||
| 56453 | JP NC,HandleOverlapSecond | Handle y when it is the smaller overlap. | ||||||||
|
This entry point is used by the routine at HandleOverlapFirst.
The z overlap is the smallest. A player whose block has the top flag set takes frame 2 and the sides of the block choose the push.
|
||||||||||
| HandleOverlap_Vertical | 56456 | LD A,(IX+0) | Remember the type. | |||||||
| 56459 | LD (54692),A | |||||||||
| 56462 | DEC A | Only the player changes frame. | ||||||||
| 56463 | JR NZ,HandleOverlap_Frame | |||||||||
| 56465 | LD A,(23768) | Read the object's flags. | ||||||||
| 56468 | RLA | Change the frame when the top flag is set. | ||||||||
| 56469 | JR NC,HandleOverlap_Frame | |||||||||
| 56471 | LD A,(IX+1) | Use the top three bits of the frame. | ||||||||
| 56474 | AND 224 | |||||||||
| 56476 | OR %00000010 | Set the frame number to 2. | ||||||||
| 56478 | LD (IX+1),A | Keep that frame. | ||||||||
| 56481 | CALL SetEntitySize | Measure the sprite. | ||||||||
| HandleOverlap_Frame | 56484 | BIT 5,(IX+1) | Move straight on when bit 5 of the frame is set. | |||||||
| 56488 | JP NZ,HandleOverlap_Move | |||||||||
| 56491 | LD D,(IX+2) | Fetch the x coordinate. | ||||||||
| 56494 | LD E,(IX+3) | |||||||||
| 56497 | LD HL,(55012) | Fetch the near x edge. | ||||||||
| 56500 | XOR A | Subtract the entity's x from the edge. | ||||||||
| 56501 | INC A | |||||||||
| 56502 | SBC HL,DE | |||||||||
| 56504 | JR Z,HandleOverlap_SizeX | The entity is on the edge. | ||||||||
| 56506 | JR NC,HandleOverlap_Push | Push back when the entity is past the edge. | ||||||||
| HandleOverlap_SizeX | 56508 | LD A,(IY+2) | Scale the object's byte up to a size along x. | |||||||
| 56511 | ADD A,A | |||||||||
| 56512 | ADD A,A | |||||||||
| 56513 | ADD A,A | |||||||||
| 56514 | ADD A,A | |||||||||
| 56515 | AND %01110000 | Use bits 4-6 of that byte. | ||||||||
| 56517 | ADD A,16 | Add 16 to make the size. | ||||||||
| 56519 | LD C,A | |||||||||
| 56520 | LD B,0 | |||||||||
| 56522 | ADD HL,BC | Add the size to the difference. | ||||||||
| 56523 | LD A,L | The push stays small when x is still inside the extent. | ||||||||
| 56524 | CP (IX+11) | |||||||||
| 56527 | LD A,2 | The small push is 2. | ||||||||
| 56529 | JR C,HandleOverlap_Push | Double the push and test y when x is clear. | ||||||||
| 56531 | ADD A,A | Double the push. | ||||||||
| 56532 | LD D,(IX+5) | Fetch the y coordinate. | ||||||||
| 56535 | LD E,(IX+6) | |||||||||
| 56538 | LD HL,(55029) | Subtract the entity's y from the near edge. | ||||||||
| 56541 | SBC HL,DE | |||||||||
| 56543 | JR Z,HandleOverlap_SizeY | The entity is on the edge. | ||||||||
| 56545 | JR NC,HandleOverlap_Push | Push back when the entity is past the edge. | ||||||||
| HandleOverlap_SizeY | 56547 | LD A,(IY+2) | Read the object's byte. | |||||||
| 56550 | ADD A,A | Double that byte. | ||||||||
| 56551 | AND %01110000 | Use bits 4-6. | ||||||||
| 56553 | ADD A,16 | Add 16 to make the size. | ||||||||
| 56555 | LD C,A | |||||||||
| 56556 | ADD HL,BC | Add the size to the difference. | ||||||||
| 56557 | LD A,L | The push stays 8 when y is still inside the extent. | ||||||||
| 56558 | CP (IX+12) | |||||||||
| 56561 | LD A,8 | The push is 8. | ||||||||
| 56563 | JR NC,HandleOverlap_Move | Move the entity when y is clear. | ||||||||
| HandleOverlap_Push | 56565 | LD B,A | Keep the push. | |||||||
| 56566 | LD A,L | Read the low byte of the difference. | ||||||||
| 56567 | BIT 7,A | Jump to HandleOverlap_Step to keep a negative difference. | ||||||||
| 56569 | JR NZ,HandleOverlap_Step | |||||||||
| 56571 | NEG | Force the difference negative. | ||||||||
| HandleOverlap_Step | 56573 | LD (55488),A | Give that step to the turn. | |||||||
| 56576 | LD A,(55357) | Read the hit already planted. | ||||||||
| 56579 | AND A | A second hit becomes 255. | ||||||||
| 56580 | JR Z,HandleOverlap_Hit | |||||||||
| 56582 | LD B,255 | A second hit is 255. | ||||||||
| HandleOverlap_Hit | 56584 | LD A,B | Plant the hit for TestEntityCells. | |||||||
| 56585 | LD (55357),A | |||||||||
|
A positive z overlap clears the vertical speed. A negative one sets it, and a saucer is left alone. The byte at 56652 is patched by TestGroupObjects: zero clears the low byte of the speed, and 4 skips that clear.
|
||||||||||
| HandleOverlap_Move | 56588 | LD HL,(56787) | Fetch the z overlap. | |||||||
| 56591 | PUSH IX | Remember the entity. | ||||||||
| 56593 | LD DE,6 | Move on to the vertical speed. | ||||||||
| 56596 | ADD IX,DE | |||||||||
| 56598 | XOR A | Clear the fraction of x. | ||||||||
| 56599 | LD (IX+4),A | |||||||||
| 56602 | BIT 7,H | A negative overlap pushes the entity up. | ||||||||
| 56604 | JR NZ,HandleOverlap_0 | |||||||||
| 56606 | LD (IX+12),A | Clear the vertical speed. | ||||||||
| 56609 | LD (IX+13),A | |||||||||
| 56612 | CALL MoveEntityBack | Move the entity back. | ||||||||
| 56615 | JR HandleOverlap_4 | Join the restore. | ||||||||
| HandleOverlap_0 | 56617 | LD A,(IX-6) | A saucer is not pushed up. | |||||||
| 56620 | CP 9 | |||||||||
| 56622 | JR Z,HandleOverlap_2 | |||||||||
| 56624 | LD A,(23768) | Read the object's flags. | ||||||||
| 56627 | RLA | The push is 253 when the top flag is set. | ||||||||
| 56628 | LD A,253 | |||||||||
| 56630 | JR C,HandleOverlap_1 | |||||||||
| 56632 | INC A | Otherwise the push is 255. | ||||||||
| 56633 | INC A | |||||||||
| HandleOverlap_1 | 56634 | LD (IX+12),A | Use that as the vertical speed. | |||||||
| 56637 | LD (IX+13),A | |||||||||
| HandleOverlap_2 | 56640 | SET 7,(IX+24) | Set bit 7 of the vertical speed and clear bit 6. | |||||||
| 56644 | RES 6,(IX+24) | |||||||||
| 56648 | CALL MoveEntityBack | Move the entity back. | ||||||||
| HandleOverlap_3 | 56651 | JR HandleOverlap_3 | Clear the low byte of the speed when the entity is inside. | |||||||
| 56653 | LD (IX+25),0 | Clear the low byte of the vertical speed. | ||||||||
| HandleOverlap_4 | 56657 | POP IX | Restore the entity. | |||||||
| 56659 | LD A,(IX+8) | Snap z up when its top byte is zero. | ||||||||
| 56662 | AND A | |||||||||
| 56663 | RET NZ | |||||||||
| 56664 | LD (IX+8),1 | Set the top of z to one. | ||||||||
| 56668 | LD (IX+9),0 | Clear the middle byte of z. | ||||||||
| 56672 | RET | Return. | ||||||||
| Prev: 56383 | Up: Map | Next: 56673 |