Is agent movement always instantaneous?

[garfieldnate]

When I disable physics auto-sim and move time forward via AdvancePhysicsStep, the agent appears to always teleport to its new position. An example illustrating this:

# demo showing that agent movement is always instantaneous
from time import sleep
from ai2thor.controller import Controller

controller = Controller(snapToGrid=False)
controller.step("PausePhysicsAutoSim")

forward = True
while True:
    if forward:
        action = "MoveAhead"
    else:
        action = "MoveBack"
    forward = not forward
    print(action)
    controller.step(action=action, moveMagnitude=0.25)
    for i in range(50):
        event = controller.step(action="AdvancePhysicsStep", timeStep=0.02)
        print(event.metadata["agent"]["position"])
        if not event.metadata["lastActionSuccess"]:
            print(event.metadata["errorMessage"])
        # no "isMoving" key!
        # print(event.metadata["agent"].keys())
    sleep(1)

This script moves the agent back and forth, calling AdvancePhysicsStep multiple times in between. I print the agent's position and also watch the Unity window, and it always appears that the agent simply moves instantaneously to its new position, as with teleportation. Here's a sample of the terminal output:

MoveAhead
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
...
MoveBack
{'x': 0.0, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.0, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.0, 'y': 0.9009992480278015, 'z': -1.25}
...
MoveAhead
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
{'x': 0.2500000298023224, 'y': 0.9009992480278015, 'z': -1.25}
...

Do I have the controller configured incorrectly here, or is continuous agent movement not possible?

(EDIT: I was not using a legal timestep. I have fixed that and added error checking. The original problem persists, and the agent teleports instead of moving continuously.)

[garfieldnate]

Someone suggested I try the ManipulaTHOR API instead, but it has a similar issue:

# demo showing that agent movement is always instantaneous
from time import sleep
from ai2thor.controller import Controller

controller = Controller(
    snapToGrid=False,
    agentMode="arm",
)
controller.step("PausePhysicsAutoSim")

forward = True
while True:
    if forward:
        print("moving forward")
        action = {
            "action": "MoveAgent",
            "ahead": 0.1,
            "speed": 1,
            "fixedDeltaTime": 0.0001,
            "disableRendering": False,
        }
    else:
        print("moving backward")
        action = {
            "action": "MoveAgent",
            "ahead": -0.1,
            "speed": 1,
            "fixedDeltaTime": 0.0001,
            "disableRendering": False,
        }
    forward = not forward
    # renders a bunch of frames showing the agent moving forward or backward for the entire specified distance
    event = controller.step(action=action)
    if not event.metadata["lastActionSuccess"]:
        raise ValueError(event.metadata["errorMessage"])
    print(action)
    for i in range(50):
        event = controller.step(action="AdvancePhysicsStep", timeStep=0.0001)
        print(event.metadata["agent"]["position"])
        if not event.metadata["lastActionSuccess"]:
            print(event.metadata["errorMessage"])
        # no "isMoving" key!
        print(event.metadata["agent"].keys())
    sleep(1)

The MoveAgent action is capable of continuous movement in the rendering and physics simulation, but the action is always completely executed before returning, despite physics auto-sim being turned off.

And now I'm getting the feeling more strongly that this API does not exist. This is what I need:

• turn off physics auto-sim
• tell agent to move
• step time forward; agent metadata indicates it is moving and whether it has collided with anything
• would probably be nice to have one more command to tell the agent to stop moving, though I think not having this could be worked around.

[garfieldnate]

I will note also that turning off physics auto-sim prevents the microwave from cooking foods.