Routines
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47287: Test Overlap In Y
Used by the routines at BlockMovementInX, BlockMovementInY, BlockMovementInZ, TestObjectIntersections and TestObjectCanBePickedUp.
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 47287 LD A,(IX+5) Fetch the depth of the first object.
47290 ADD A,(IY+5) Add the depth of the second object.
47293 LD D,A Copy the total to D.
Work out the distance between the centres, once the first has moved.
47294 LD A,(IX+2) Fetch the y position of the first object.
47297 ADD A,L Add L.
47298 SUB (IY+2) Subtract the y position of the second object.
47301 JP P,TestOverlapInY_Compare Jump to TestOverlapInY_Compare if the distance is positive.
47304 NEG Negate A.
TestOverlapInY_Compare 47306 SUB D Subtract D.
47307 RET Return.
View the equivalent code in;
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