if (this_index - last_index > points_in_line/2)
while (this_index - last_index > points_in_line/2)
this_index -= points_in_line;
else if (last_index - this_index > points_in_line/2)
while (last_index - this_index > points_in_line/2)
this_index += points_in_line;
if (this_index - last_index > points_in_line/2)
while (this_index - last_index > points_in_line/2)
this_index -= points_in_line;
else if (last_index - this_index > points_in_line/2)
while (last_index - this_index > points_in_line/2)
this_index += points_in_line;