Adjacent Lanelets with oposite directions

[francocipollone]

Context

Lanelets support having different directions for adjacent lanelets (what we could call a maliput:api::Segment), it is achieved by inverting the order of the linestrings, for example for two adjacent lanelets:

A  -------->
B  -------->
C <-------

Lanelet AB's direction is west-east
Lanelet CB's direction is east-west (It is achieved by inverting the B linestring)

For these two lanelets as they have opposite directions, lanelet2 doesn't support passing/driving from one lane to the other.
In our case(maliput_osm), as the code stands, we are considering AB and CB as lanelets that belong to the same direction (as AB), ergo same maliput segment.

Note: Actually we haven't changed anything to do so, the lanelet2's api for getting the right and left boundaries automatically invert the boundaries:

  ConstLineString3d Lanelet::rightBound3d() const {
    return inverted() ? constData()->leftBound().invert() : constData()->rightBound();
  }

Proposal

When parsing the lanelets we should check those linestrings that are inverted and derive a direction usage rule to be AgainstS.

Extra

I leave here just a python script for creating a map using an inverted linestring for the shared linestring.

Click to see script

    map = LaneletMap()
    ls_at_2 = LineString3d(getId(), [Point3d(getId(), i, 2, 0) for i in range(0, 3)]) # y=2
    ls_at_4 = LineString3d(getId(), [Point3d(getId(), i, 4, 0) for i in range(0, 3)]) # y=4
    ls_at_2_inv = ls_at_2.invert()
    ls_at_0 = LineString3d(getId(), [Point3d(getId(), i, 0, 0) for i in range(2, -1, -1)]) # y=0
    lanelet = Lanelet(getId(), ls_at_4, ls_at_2)
    lanelet2 = Lanelet(getId(), ls_at_2_inv, ls_at_0)
    map.add(lanelet)
    map.add(lanelet2)
    path = os.path.join('./mapfile.osm')
    projector = UtmProjector(Origin(0, 0))
    write(path, map, projector)
    mapLoad, errors = loadRobust(path, projector)
    assert not errors
    assert mapLoad.laneletLayer.exists(lanelet.id)

    gotten_lanelet = mapLoad.laneletLayer[lanelet.id]
    gotten_lanelet2 = mapLoad.laneletLayer[lanelet2.id]
    print(gotten_lanelet)
    print("\tleft_bound: " + str(gotten_lanelet.leftBound))
    print("\tright_bound: " + str(gotten_lanelet.rightBound))
    print(gotten_lanelet2)
    print("\tleft_bound: " + str(gotten_lanelet2.leftBound))
    print("\tright_bound: " + str(gotten_lanelet2.rightBound))