vec_dist only accepts VECTOR pointers, write
distance = vec_dist(my.x,marker.x);
instead.
Btw on low framerates distance probably will never be 1 or less, example:
- fps == 16, then time_step will be 1
- situation in one arbitrary frame: marker.x/z = my.x/z, marker.y = 10, my.y = 12.3
my.y -= 5;
- situation next frame: marker.y = 10, my.y = 7.3
...
my.y = 2.3, -3.3, ...
=> distance will never be smaller than 2.3