Routines
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50643: Test Overlap In Z
Used by the routines at TestObjectIntersections, TestNearObject, BlockMovementInX, BlockMovementInY and BlockMovementInZ.
Tests whether two objects overlap along z, once the first has moved by its new speed along z. They overlap when the distance between the z positions is smaller than the height of whichever of the objects is lower.
Input
H New speed along z of the first object
IX The address of the first object
IY The address of the second object
Output
F Carry flag set if the objects overlap
Use the height of the lower object.
TestOverlapInZ 50643 LD A,(IX+3) Fetch the z position of the first object.
50646 ADD A,H Add H.
50647 SUB (IY+3) Subtract the z position of the second object.
50650 JP P,TestOverlapInZ_Second Jump to TestOverlapInZ_Second if the sign flag is clear.
50653 NEG Negate A.
50655 LD D,(IX+6) Fetch the height of the first object.
TestOverlapInZ_Compare 50658 SUB D Subtract D.
50659 RET Return.
TestOverlapInZ_Second 50660 LD D,(IY+6) Fetch the height of the second object.
50663 JR TestOverlapInZ_Compare Jump to TestOverlapInZ_Compare.
View the equivalent code in;
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