A NavMesh is a feature of the underlying Unity Engine that can generate basic pathfinding data for agents. In TDW, if a scene has a NavMesh you can receive path data, where a path is a list of (x, y, z) positions.
A NavMesh is a static data object in a Unity scene. It must be baked in order to be used for navigation. It isn't possible to view the NavMesh in TDW; however, this is what it looks like in the Unity Editor (the software used to develop Unity projects):
TDW objects can optionally receive a NavMeshObstacle Unity component. If added, they will carve a hole in the NavMesh:
The NavMesh add-on simplifies the process of baking a NavMesh and adding NavMeshObstacles:
from tdw.tdw_utils import TDWUtils
from tdw.controller import Controller
from tdw.add_ons.nav_mesh import NavMesh
c = Controller()
c.add_ons.append(NavMesh())
c.communicate([TDWUtils.create_empty_room(12, 12)])
c.communicate([])Result:
Notice that the NavMesh add-on requires two communicate() calls to initialize:
- In the first communicate() call, the
NavMeshadd-on requests output data:StaticRigidbodiesto determine which objects are kinematic,Boundsto get the size and position of each object, andStaticRobotto get robot IDs (robots are ignored when baking the NavMesh). - In the second communicate() call, the
NavMeshadd-on parses the output data. Depending on the size and position of each object, the add-on makes the object a NavMeshObstacle viamake_nav_mesh_obstacleand then bakes the NavMesh viabake_nav_mesh.
In this example, two objects carve holes in the NavMesh:
from tdw.tdw_utils import TDWUtils
from tdw.controller import Controller
from tdw.add_ons.nav_mesh import NavMesh
c = Controller()
c.add_ons.append(NavMesh())
c.communicate([TDWUtils.create_empty_room(12, 12),
c.get_add_object(model_name="trunck",
object_id=0,
position={"x": 0, "y": 0, "z": 0}),
c.get_add_object(model_name="rh10",
object_id=1,
position={"x": -1, "y": 0, "z": 1.5})])
c.communicate([])Result:
In the above example, the two objects have NavMeshObstacle components. The NavMesh add-on includes many optional constructor parameters that will help you adjust which objects receive NavMeshObstacle components, the size of each NavMeshObstacle, etc. For example, exclude_objects is an optional list of object IDs for objects if you want certain objects to not be NavMeshObstacles.
Read the API documentation for a full list of optional constructor parameters.
After initializing the NavMesh add-on, you can request NavMeshPath output data by sending send_nav_mesh_path. NavMeshPath includes a path (a numpy array of [x, y, z] coordinates) and a state (complete, partial, or invalid).
In this example, we'll create a scene with a NavMesh and find a path between two points. Notice that we send send_nav_mesh_path after the scene is created because the NavMesh add-on requires two communicate() calls to initialize.
from tdw.tdw_utils import TDWUtils
from tdw.controller import Controller
from tdw.output_data import OutputData, NavMeshPath
from tdw.add_ons.nav_mesh import NavMesh
c = Controller()
c.add_ons.append(NavMesh())
c.communicate([TDWUtils.create_empty_room(12, 12),
c.get_add_object(model_name="trunck",
object_id=0,
position={"x": 0, "y": 0, "z": 0}),
c.get_add_object(model_name="rh10",
object_id=1,
position={"x": -1, "y": 0, "z": 1.5})])
resp = c.communicate({"$type": "send_nav_mesh_path",
"origin": {"x": 0.1, "y": 0, "z": -1.3},
"destination": {"x": -0.13, "y": 0, "z": 4}})
for i in range(len(resp) - 1):
r_id = OutputData.get_data_type_id(resp[i])
if r_id == "path":
nav_mesh_path = NavMeshPath(resp[i])
print(nav_mesh_path.get_state())
for point in nav_mesh_path.get_path():
print(point)
c.communicate({"$type": "terminate"})Output:
complete
[ 0.1 0.08333325 -1.3 ]
[-0.9404912 0.08333325 -0.844499 ]
[-0.9404912 0.08333325 0.83449864]
[-0.13 0.08333325 4. ]
An agent can then use this data to pathfind. In this example, we'll use a Magnebot agent:
from tdw.tdw_utils import TDWUtils
from tdw.controller import Controller
from tdw.output_data import OutputData, NavMeshPath
from tdw.add_ons.third_person_camera import ThirdPersonCamera
from tdw.add_ons.image_capture import ImageCapture
from tdw.add_ons.nav_mesh import NavMesh
from tdw.backend.paths import EXAMPLE_CONTROLLER_OUTPUT_PATH
from magnebot import Magnebot, ActionStatus
c = Controller()
magnebot = Magnebot(position={"x": 0.1, "y": 0, "z": -1.3},
robot_id=c.get_unique_id())
magnebot.collision_detection.objects = False
camera = ThirdPersonCamera(position={"x": 0, "y": 8, "z": 0},
look_at={"x": 0, "y": 0, "z": 0},
avatar_id="c")
path = EXAMPLE_CONTROLLER_OUTPUT_PATH.joinpath("nav_mesh")
print(f"Images will be saved to: {path}")
capture = ImageCapture(avatar_ids=["c"], path=path)
nav_mesh = NavMesh(exclude_objects=[magnebot.robot_id])
c.add_ons.extend([magnebot, camera, capture, nav_mesh])
# Create the scene and add an object. This will also tell the NavMesh add-on to request the output data it needs.
c.communicate([TDWUtils.create_empty_room(12, 12),
c.get_add_object(model_name="trunck",
object_id=0,
position={"x": 0, "y": 0, "z": 0}),
c.get_add_object(model_name="rh10",
object_id=1,
position={"x": -1, "y": 0, "z": 1.5})])
# Add NavMeshObstacles, bake the NavMesh, and request a path.
resp = c.communicate({"$type": "send_nav_mesh_path",
"origin": {"x": 0.1, "y": 0, "z": -1.3},
"destination": {"x": -2, "y": 0, "z": 4}})
path = []
for i in range(len(resp) - 1):
r_id = OutputData.get_data_type_id(resp[i])
if r_id == "path":
nav_mesh_path = NavMeshPath(resp[i])
path = nav_mesh_path.get_path()
break
for point in path[1:]:
p = TDWUtils.array_to_vector3(point)
p["y"] = 0
magnebot.move_to(target=p)
while magnebot.action.status == ActionStatus.ongoing:
c.communicate([])
c.communicate([])
c.communicate({"$type": "terminate"})Result:
Next: Occupancy maps
External APIs:
Example controllers:
- nav_mesh.py Add a Magnebot to the scene and navigate using a NavMesh.
Python API:
NavMeshThe NavMesh add-on.
Command API:
Output Data: