Now, I like to believe that for curve inclined at various different angles, the essence of `r` would be to compute the perpendicular distance to this curve using the difference in `u` values (which depends on the direction of the curve), since the curve always travels normal to itself and with unit speed, the perpendicular distance from the curve to `?` should give me the answer. I just add an offset in time to keep the `u` values always progressing ahead in time, which is what `s` does here.