Routines
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50622: 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 50622 LD A,(IX+5) Fetch the depth of the first object.
50625 ADD A,(IY+5) Add the depth of the second object.
50628 LD D,A Copy the total to D.
50629 LD A,(IX+2) Fetch the y position of the first object.
50632 ADD A,L Add L.
50633 SUB (IY+2) Subtract the y position of the second object.
50636 JP P,TestOverlapInY_Compare Jump to TestOverlapInY_Compare if the sign flag is clear.
50639 NEG Negate A.
TestOverlapInY_Compare 50641 SUB D Subtract D.
50642 RET Return.
View the equivalent code in;
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