Routines
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35575: Position Mask Sprite
Convert the actor's world position into a screen column. If it is on screen, work out the pixel shift, the screen address and the sprite size, and cache them on the actor.
Input
IX Actor slot
PositionMaskSprite 35575 LD L,(IX+2) Fetch the actor's world X position.
35578 LD H,(IX+3)
35581 LD BC,(24698) Subtract the scroll position at Jetman_Position.
35585 AND A
35586 SBC HL,BC
35588 LD BC,120 Add the 0120 draw offset.
35591 ADD HL,BC
35592 LD A,H Fetch the high byte of the screen column.
35593 AND %00011111 Keep only bits 0-4.
35595 JP NZ,ResetSpriteFields Jump to ResetSpriteFields if the actor is off-screen.
35598 LD (IX+1),L Store the screen column in *IX+1.
Look up the sprite graphic and work out the pixel shift from the screen column.
35601 CALL FetchActorSprite Call FetchActorSprite.
35604 LD L,(IX+1) Fetch the screen column and actor Y.
35607 LD H,(IX+4)
35610 LD A,L Build a pixel-shift index from the column.
35611 DEC A
35612 AND %00000111 Keep only bits 0-2.
35614 CP 7 Jump to PositionMaskSprite_StoreShift if the shift is not 7.
35616 JR NZ,PositionMaskSprite_StoreShift
35618 LD A,242 Set the shift operand to 242.
PositionMaskSprite_StoreShift 35620 LD (35537),A Write the shift to 35537 and *IX+9.
35623 LD (IX+9),A
Choose the scratch width for the shift.
35626 LD A,1 Set the scratch width to 1.
35628 JR Z,PositionMaskSprite_StoreWidth Jump to PositionMaskSprite_StoreWidth if the shift was 7.
35630 INC A Widen the scratch width to 2.
PositionMaskSprite_StoreWidth 35631 LD (24151),A Write the scratch width and cache the actor Y.
35634 LD (IX+11),H
Work out the screen address, then cache the sprite size and pointers on the actor.
35637 CALL ScreenAddress Call ScreenAddress.
35640 LD A,(DE) Copy the sprite height into SpriteRowsLeft, SpriteHeight and *IX+10.
35641 INC DE
35642 LD (24153),A
35645 LD (24152),A
35648 LD (IX+10),A
35651 LD (IX+12),E Cache the graphic pointer and screen address on the actor.
35654 LD (IX+13),D
35657 LD (IX+14),L
35660 LD (IX+15),H
35663 LD C,0 Clear the row counter.
35665 RET Return.
Prev: 35560 Up: Map Next: 35666