Routines
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C5BE: Test Overlap In Y
Used by the routines at TestObjectIntersections, TestNearObject, BlockMovementInX, BlockMovementInY and BlockMovementInZ.
Tests whether two objects overlap along y, once the first has moved by its new speed along y. They overlap when the distance between the y positions is smaller than the two depths added together.
Input
L New speed along y 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
Compare the y distance with the depths.
TestOverlapInY C5BE LD A,(IX+$05) Fetch the depth of the first object.
C5C1 ADD A,(IY+$05) Add the depth of the second object.
C5C4 LD D,A Copy the total to D.
C5C5 LD A,(IX+$02) Fetch the y position of the first object.
C5C8 ADD A,L Add L.
C5C9 SUB (IY+$02) Subtract the y position of the second object.
C5CC JP P,TestOverlapInY_Compare Jump to TestOverlapInY_Compare if the sign flag is clear.
C5CF NEG Negate A.
TestOverlapInY_Compare C5D1 SUB D Subtract D.
C5D2 RET Return.
View the equivalent code in;
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