Routines
Prev: 47287 Up: Map Next: 47330
47308: Test Overlap In Z
Used by the routines at BlockMovementInX, BlockMovementInY, BlockMovementInZ, TestObjectIntersections and TestObjectCanBePickedUp.
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 47308 LD A,(IX+3) Fetch the z position of the first object.
47311 ADD A,H Add H.
47312 SUB (IY+3) Subtract the z position of the second object.
47315 JP P,TestOverlapInZ_SecondLower Jump to TestOverlapInZ_SecondLower if the first object is the higher.
47318 NEG Negate A.
47320 LD D,(IX+6) Fetch the height of the first object, which is the lower.
Compare the distance with the height of the lower object.
TestOverlapInZ_Compare 47323 SUB D Subtract the height of the lower object, which sets the carry flag if they overlap.
47324 RET Return.
TestOverlapInZ_SecondLower 47325 LD D,(IY+6) Fetch the height of the second object, which is the lower.
47328 JR TestOverlapInZ_Compare Jump to TestOverlapInZ_Compare.
View the equivalent code in;
Prev: 47287 Up: Map Next: 47330