vec_dist(my.y, rogue.y)
is not a valid use of the function and vectors in general. vec_dist has 2 VECTOR* parameters, not vars, thus the function will assume
(my.y,my.z, whatever follows in the memory)
as the vector you want to use.
The "distance" of two vars obviously is abs(my.y-rogue.y); which is equal to but faster than vec_dist(vector(0,my.y,0),vector(0,rogue.y,0));