Routines
Prev: DB24 Up: Map Next: DBC9
DB3F: Test Actor Collision
Used by the routines at Handler_Player and Handler_Actors.
Reverses the actor at a destination. On a player hit, copies the actor deltas onto Player.
Input
IY Actor record
Reverse at the destination when cell-aligned.
Test_ActorCollision DB3F LD A,(IY+$08) Jump to Test_ActorCollision_Column if the horizontal delta is set.
DB42 OR A
DB43 JR NZ,Test_ActorCollision_Column
Test the destination row.
DB45 LD A,$07 Jump to Test_ActorCollision_Bounds unless the fine-Y is 07.
DB47 CP (IY+$03)
DB4A JR NZ,Test_ActorCollision_Bounds
DB4C LD A,(IY+$01) Call Actor_Reverse if the row matches the destination.
DB4F CP (IY+$06)
DB52 CALL Z,Actor_Reverse
DB55 JR Test_ActorCollision_Bounds Jump to Test_ActorCollision_Bounds.
Test the destination column.
Test_ActorCollision_Column DB57 LD A,$07 Jump to Test_ActorCollision_Bounds unless the fine-X is 07.
DB59 CP (IY+$02)
DB5C JR NZ,Test_ActorCollision_Bounds
DB5E LD A,(IY+$00) Call Actor_Reverse if the column matches the destination.
DB61 CP (IY+$05)
DB64 CALL Z,Actor_Reverse
Skip the hit test while jumping or falling.
Test_ActorCollision_Bounds DB67 LD A,($6410) Return if *Player_JumpTimer is set.
DB6A OR A
DB6B RET NZ
Require a close vertical overlap.
DB6C LD A,(IY+$01) Convert the actor row and fine-Y into a pixel row.
DB6F ADD A,A
DB70 ADD A,A
DB71 ADD A,A
DB72 ADD A,(IY+$03)
DB75 LD C,A
Convert the player row the same way.
DB76 LD A,($64A7) Convert the player row and fine-Y into a pixel row.
DB79 LD B,A
DB7A LD A,($64A5)
DB7D SUB $03
DB7F ADD A,A
DB80 ADD A,A
DB81 ADD A,A
DB82 ADD A,B
DB83 SUB C Return unless the difference is less than 04.
DB84 CP $04
DB86 RET NC
Keep the gap and convert the actor column.
DB87 LD D,A Keep the vertical gap in D.
DB88 LD A,(IY+$00) Convert the actor column and fine-X into a pixel column.
DB8B DEC A
DB8C DEC A
DB8D ADD A,A
DB8E ADD A,A
DB8F ADD A,A
DB90 ADD A,(IY+$02)
DB93 LD B,A
Build the overlap limit.
DB94 LD A,($6449) Copy the footprint offset into C.
DB97 LD C,A
DB98 LD A,(IY+$04) Write the actor pixel width plus that offset into *DBAD.
DB9B ADD A,A
DB9C ADD A,A
DB9D ADD A,A
DB9E ADD A,C
DB9F DEC A
DBA0 LD ($DBAD),A
Test the player width against the actor column.
DBA3 SUB C Restore the actor pixel width in C.
DBA4 LD C,A
DBA5 INC C
DBA6 LD A,($6448) Return unless the ranges overlap.
DBA9 ADD A,C
DBAA SUB B
DBAB DEC A
DBAC CP $C8
DBAE RET NC
Copy the actor movement onto the player.
DBAF LD A,(IY+$08) Write the horizontal delta to *Player_HorizontalDelta.
DBB2 LD ($64AC),A
DBB5 LD A,$03 Write 03 to *CollisionState.
DBB7 LD ($6434),A
Adjust the vertical delta by the gap.
DBBA LD A,(IY+$09) Jump to Test_ActorCollision_Store if the vertical delta is zero.
DBBD OR A
DBBE JR Z,Test_ActorCollision_Store
DBC0 SUB D Subtract the vertical gap.
Store the vertical delta and the actor.
Test_ActorCollision_Store DBC1 LD ($64AD),A Write the vertical delta to *Player_VerticalDelta.
DBC4 LD ($644B),IY Write the actor pointer to *Pointer_CollidedActor.
DBC8 RET Return.
Prev: DB24 Up: Map Next: DBC9