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Physics (PhysX)

Rigidbodies output data

Send the command send_rigidbodies to receive Rigidbodies dynamic data (data that changes per-frame such as velocity). Send send_static_rigidbodies to receive StaticRigidbodies static data (data that isn't expected to change per-frame such as mass).

Rigidbodies output data also contains:

  • Object ID
  • Velocity (the directional velocity)
  • Angular velocity
  • Sleeping: PhysX makes a low-level distinction between objects that are moving and objects that are inert; inert objects are considered "sleeping".

StaticRigidbodies output data contains:

from tdw.controller import Controller
from tdw.tdw_utils import TDWUtils
from tdw.output_data import OutputData, Rigidbodies, StaticRigidbodies

c = Controller()
resp = c.communicate([TDWUtils.create_empty_room(12, 12),
                      c.get_add_object(model_name="iron_box",
                                       position={"x": 0, "y": 3, "z": 0},
                                       object_id=c.get_unique_id()),
                      {"$type": "send_rigidbodies",
                       "frequency": "always"},
                      {"$type": "send_static_rigidbodies",
                       "frequency": "once"}])

for i in range(len(resp) - 1):
    r_id = OutputData.get_data_type_id(resp[i])
    if r_id == "rigi":
        rigi = Rigidbodies(resp[i])
        for j in range(rigi.get_num()):
            object_id = rigi.get_id(j)
            velocity = rigi.get_velocity(j)
            angular_velocity = rigi.get_angular_velocity(j)
            sleeping = rigi.get_sleeping(j)
    elif r_id == "srig":
        srig = StaticRigidbodies(resp[i])
        for j in range(srig.get_num()):
            object_id = srig.get_id(j)
            mass = srig.get_mass(j)
            kinematic = srig.get_kinematic(j)
            dynamic_friction = srig.get_dynamic_friction(j)
            static_friction = srig.get_static_friction(j)
            bounciness = srig.get_bounciness(j)
c.communicate({"$type": "terminate"})

The ObjectManager add-on

We've seen the ObjectManager add-on in the Core Concepts documentation. If you need to frequently use rigidbody data, you can use the ObjectManager which will conveniently sort all rigidbody data by object per frame. If rigidbodies=True in the constructor, the ObjectManager will send send_rigidbodies when it is first initialized and parse Rigidbodies data per frame.

Note that in Rigidbodies output data, velocity and angular velocity as (x, y, z) tuples, but in the ObjectManager these parameters are conveniently converted into numpy arrays.

Static rigidbody data is always cached in objects_static regardless of whether rigidbodies=True.

from tdw.controller import Controller
from tdw.tdw_utils import TDWUtils
from tdw.add_ons.object_manager import ObjectManager

c = Controller()
c.communicate(TDWUtils.create_empty_room(12, 12))

# Add the object manager.
object_manager = ObjectManager(transforms=True, rigidbodies=True)
c.add_ons.extend([object_manager])
object_id = c.get_unique_id()
# Add the object.
c.communicate(c.get_add_physics_object(model_name="iron_box",
                                       object_id=object_id,
                                       position={"x": 0, "y": 7, "z": 0}))

for o_id in object_manager.objects_static:
    print(o_id, object_manager.objects_static[o_id].mass)

# Let the object fall.
while not object_manager.rigidbodies[object_id].sleeping:
    print(object_manager.rigidbodies[object_id].velocity)
    c.communicate([])
c.communicate({"$type": "terminate"})

Next: Collision output data

Return to the README

Example controllers:

  • physics_values.py Drop an object with varying physics values and observe its behavior.

Python API:

Command API:

Output Data API: