Moves InteractiveScene entities from class to instance variables (#466)

# Description

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Currently, InteractiveScene declares several of its entities
(articulation, sensor, and rigid bodies) as class variables. This causes
the variables to be shared across **all** instances of the class, which
is not desired behavior if there is ever a case when `InteractiveScene`
is used more than once.

This fix changes the following: 

1. All class variables in `InteractiveScene` defined above the
constructor is now moved inside the constructor as instance variables.
2. Adds `@property` getters to access the entities. 
3. Rolls back the fix introduced in #380, which changes the `__del__`
magic method to clear out the class variables that persisted, but ended
up breaking #464.

Fixes #465 

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## Type of change

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applicable. -->

- Bug fix (non-breaking change which fixes an issue)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have run all the tests with `./orbit.sh --test` and they pass
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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source/extensions/omni.isaac.orbit/config/extension.toml

 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.15.2"
+version = "0.15.3"
 
 # Description
 title = "ORBIT framework for Robot Learning"

source/extensions/omni.isaac.orbit/docs/CHANGELOG.rst

 Changelog
 ---------
 
+0.15.3 (2024-03-21)
+~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added unit test to check that :class:`omni.isaac.orbit.scene.InteractiveScene` entity data is not shared between separate instances.
+
+Fixed
+^^^^^
+* Moved class variables in :class:`omni.isaac.orbit.scene.InteractiveScene` to correctly  be assigned as
+  instance variables.
+* Removed custom ``__del__`` magic method from :class:`omni.isaac.orbit.scene.InteractiveScene`.
+
+
 0.15.2 (2024-03-21)
 ~~~~~~~~~~~~~~~~~~~
 

source/extensions/omni.isaac.orbit/omni/isaac/orbit/scene/interactive_scene.py

@@ -69,36 +69,6 @@ class InteractiveScene:
         for more details.
     """
 
-    terrain: TerrainImporter | None = None
-    """The terrain in the scene. If None, then the scene has no terrain.
-
-    Note:
-        We treat terrain separate from :attr:`extras` since terrains define environment origins and are
-        handled differently from other miscellaneous entities.
-    """
-    articulations: dict[str, Articulation] = dict()
-    """A dictionary of articulations in the scene."""
-    rigid_objects: dict[str, RigidObject] = dict()
-    """A dictionary of rigid objects in the scene."""
-    sensors: dict[str, SensorBase] = dict()
-    """A dictionary of the sensors in the scene, such as cameras and contact reporters."""
-    extras: dict[str, XFormPrimView] = dict()
-    """A dictionary of miscellaneous simulation objects that neither inherit from assets nor sensors.
-
-    The keys are the names of the miscellaneous objects, and the values are the `XFormPrimView`_
-    of the corresponding prims.
-
-    As an example, lights or other props in the scene that do not have any attributes or properties that you
-    want to alter at runtime can be added to this dictionary.
-
-    Note:
-        These are not reset or updated by the scene. They are mainly other prims that are not necessarily
-        handled by the interactive scene, but are useful to be accessed by the user.
-
-    .. _XFormPrimView: https://docs.omniverse.nvidia.com/py/isaacsim/source/extensions/omni.isaac.core/docs/index.html#omni.isaac.core.prims.XFormPrimView
-
-    """
-
     def __init__(self, cfg: InteractiveSceneCfg):
         """Initializes the scene.
 
@@ -107,6 +77,12 @@ class InteractiveScene:
         """
         # store inputs
         self.cfg = cfg
+        # initialize scene elements
+        self._terrain = None
+        self._articulations = dict()
+        self._rigid_objects = dict()
+        self._sensors = dict()
+        self._extras = dict()
         # obtain the current stage
         self.stage = omni.usd.get_context().get_stage()
         # prepare cloner for environment replication
@@ -149,12 +125,6 @@ class InteractiveScene:
             global_paths=self._global_prim_paths,
         )
 
-    def __del__(self):
-        """Clear instances of registered assets and sensors."""
-        self.articulations.clear()
-        self.rigid_objects.clear()
-        self.sensors.clear()
-
     def __str__(self) -> str:
         """Returns a string representation of the scene."""
         msg = f"<class {self.__class__.__name__}>\n"
@@ -201,11 +171,55 @@ class InteractiveScene:
     @property
     def env_origins(self) -> torch.Tensor:
         """The origins of the environments in the scene. Shape is (num_envs, 3)."""
-        if self.terrain is not None:
-            return self.terrain.env_origins
+        if self._terrain is not None:
+            return self._terrain.env_origins
         else:
             return self._default_env_origins
 
+    @property
+    def terrain(self) -> TerrainImporter | None:
+        """The terrain in the scene. If None, then the scene has no terrain.
+
+        Note:
+            We treat terrain separate from :attr:`extras` since terrains define environment origins and are
+            handled differently from other miscellaneous entities.
+        """
+        return self._terrain
+
+    @property
+    def articulations(self) -> dict[str, Articulation]:
+        """A dictionary of articulations in the scene."""
+        return self._articulations
+
+    @property
+    def rigid_objects(self) -> dict[str, RigidObject]:
+        """A dictionary of rigid objects in the scene."""
+        return self._rigid_objects
+
+    @property
+    def sensors(self) -> dict[str, SensorBase]:
+        """A dictionary of the sensors in the scene, such as cameras and contact reporters."""
+        return self._sensors
+
+    @property
+    def extras(self) -> dict[str, XFormPrimView]:
+        """A dictionary of miscellaneous simulation objects that neither inherit from assets nor sensors.
+
+        The keys are the names of the miscellaneous objects, and the values are the `XFormPrimView`_
+        of the corresponding prims.
+
+        As an example, lights or other props in the scene that do not have any attributes or properties that you
+        want to alter at runtime can be added to this dictionary.
+
+        Note:
+            These are not reset or updated by the scene. They are mainly other prims that are not necessarily
+            handled by the interactive scene, but are useful to be accessed by the user.
+
+        .. _XFormPrimView: https://docs.omniverse.nvidia.com/py/isaacsim/source/extensions/omni.isaac.core/docs/index.html#omni.isaac.core.prims.XFormPrimView
+
+        """
+        return self._extras
+
     """
     Operations.
     """
@@ -218,12 +232,12 @@ class InteractiveScene:
                 Defaults to None (all instances).
         """
         # -- assets
-        for articulation in self.articulations.values():
+        for articulation in self._articulations.values():
             articulation.reset(env_ids)
-        for rigid_object in self.rigid_objects.values():
+        for rigid_object in self._rigid_objects.values():
             rigid_object.reset(env_ids)
         # -- sensors
-        for sensor in self.sensors.values():
+        for sensor in self._sensors.values():
             sensor.reset(env_ids)
         # -- flush physics sim view if called in extension mode
         # this is needed when using PhysX GPU pipeline since the data needs to be sent to the underlying
@@ -236,9 +250,9 @@ class InteractiveScene:
     def write_data_to_sim(self):
         """Writes the data of the scene entities to the simulation."""
         # -- assets
-        for articulation in self.articulations.values():
+        for articulation in self._articulations.values():
             articulation.write_data_to_sim()
-        for rigid_object in self.rigid_objects.values():
+        for rigid_object in self._rigid_objects.values():
             rigid_object.write_data_to_sim()
         # -- flush physics sim view if called in extension mode
         # this is needed when using PhysX GPU pipeline since the data needs to be sent to the underlying
@@ -255,12 +269,12 @@ class InteractiveScene:
             dt: The amount of time passed from last :meth:`update` call.
         """
         # -- assets
-        for articulation in self.articulations.values():
+        for articulation in self._articulations.values():
             articulation.update(dt)
-        for rigid_object in self.rigid_objects.values():
+        for rigid_object in self._rigid_objects.values():
             rigid_object.update(dt)
         # -- sensors
-        for sensor in self.sensors.values():
+        for sensor in self._sensors.values():
             sensor.update(dt, force_recompute=not self.cfg.lazy_sensor_update)
 
     """
@@ -274,7 +288,7 @@ class InteractiveScene:
             The keys of the scene entities.
         """
         all_keys = ["terrain"]
-        for asset_family in [self.articulations, self.rigid_objects, self.sensors, self.extras]:
+        for asset_family in [self._articulations, self._rigid_objects, self._sensors, self._extras]:
             all_keys += list(asset_family.keys())
         return all_keys
 
@@ -289,11 +303,11 @@ class InteractiveScene:
         """
         # check if it is a terrain
         if key == "terrain":
-            return self.terrain
+            return self._terrain
 
         all_keys = ["terrain"]
         # check if it is in other dictionaries
-        for asset_family in [self.articulations, self.rigid_objects, self.sensors, self.extras]:
+        for asset_family in [self._articulations, self._rigid_objects, self._sensors, self._extras]:
             out = asset_family.get(key)
             # if found, return
             if out is not None:
@@ -323,11 +337,11 @@ class InteractiveScene:
                 # terrains are special entities since they define environment origins
                 asset_cfg.num_envs = self.cfg.num_envs
                 asset_cfg.env_spacing = self.cfg.env_spacing
-                self.terrain = asset_cfg.class_type(asset_cfg)
+                self._terrain = asset_cfg.class_type(asset_cfg)
             elif isinstance(asset_cfg, ArticulationCfg):
-                self.articulations[asset_name] = asset_cfg.class_type(asset_cfg)
+                self._articulations[asset_name] = asset_cfg.class_type(asset_cfg)
             elif isinstance(asset_cfg, RigidObjectCfg):
-                self.rigid_objects[asset_name] = asset_cfg.class_type(asset_cfg)
+                self._rigid_objects[asset_name] = asset_cfg.class_type(asset_cfg)
             elif isinstance(asset_cfg, SensorBaseCfg):
                 # Update target frame path(s)' regex name space for FrameTransformer
                 if isinstance(asset_cfg, FrameTransformerCfg):
@@ -337,7 +351,7 @@ class InteractiveScene:
                         updated_target_frames.append(target_frame)
                     asset_cfg.target_frames = updated_target_frames
 
-                self.sensors[asset_name] = asset_cfg.class_type(asset_cfg)
+                self._sensors[asset_name] = asset_cfg.class_type(asset_cfg)
             elif isinstance(asset_cfg, AssetBaseCfg):
                 # manually spawn asset
                 if asset_cfg.spawn is not None:
@@ -349,7 +363,7 @@ class InteractiveScene:
                     )
                 # store xform prim view corresponding to this asset
                 # all prims in the scene are Xform prims (i.e. have a transform component)
-                self.extras[asset_name] = XFormPrimView(asset_cfg.prim_path, reset_xform_properties=False)
+                self._extras[asset_name] = XFormPrimView(asset_cfg.prim_path, reset_xform_properties=False)
             else:
                 raise ValueError(f"Unknown asset config type for {asset_name}: {asset_cfg}")
             # store global collision paths

source/extensions/omni.isaac.orbit/test/scene/test_interactive_scene.py

+# Copyright (c) 2022-2024, The ORBIT Project Developers.
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+from __future__ import annotations
+
+"""Launch Isaac Sim Simulator first."""
+
+from omni.isaac.orbit.app import AppLauncher
+
+# launch omniverse app
+simulation_app = AppLauncher(headless=True).app
+
+"""Rest everything follows."""
+
+import unittest
+
+import omni.isaac.orbit.sim as sim_utils
+from omni.isaac.orbit.actuators import ImplicitActuatorCfg
+from omni.isaac.orbit.assets import ArticulationCfg, AssetBaseCfg, RigidObjectCfg
+from omni.isaac.orbit.scene import InteractiveScene, InteractiveSceneCfg
+from omni.isaac.orbit.sensors import ContactSensorCfg
+from omni.isaac.orbit.sim import build_simulation_context
+from omni.isaac.orbit.terrains import TerrainImporterCfg
+from omni.isaac.orbit.utils import configclass
+from omni.isaac.orbit.utils.assets import ISAAC_NUCLEUS_DIR
+
+
+@configclass
+class MySceneCfg(InteractiveSceneCfg):
+    """Example scene configuration."""
+
+    # terrain - flat terrain plane
+    terrain = TerrainImporterCfg(
+        prim_path="/World/ground",
+        terrain_type="plane",
+    )
+
+    # articulation
+    robot = ArticulationCfg(
+        prim_path="/World/Robot",
+        spawn=sim_utils.UsdFileCfg(usd_path=f"{ISAAC_NUCLEUS_DIR}/Robots/Simple/revolute_articulation.usd"),
+        actuators={
+            "joint": ImplicitActuatorCfg(),
+        },
+    )
+    # rigid object
+    rigid_obj = RigidObjectCfg(
+        prim_path="/World/RigidObj",
+        spawn=sim_utils.CuboidCfg(
+            size=(0.5, 0.5, 0.5),
+            rigid_props=sim_utils.RigidBodyPropertiesCfg(
+                disable_gravity=False,
+            ),
+            collision_props=sim_utils.CollisionPropertiesCfg(
+                collision_enabled=True,
+            ),
+        ),
+    )
+
+    # sensor
+    sensor = ContactSensorCfg(
+        prim_path="/World/Robot",
+    )
+    # extras - light
+    light = AssetBaseCfg(
+        prim_path="/World/light",
+        spawn=sim_utils.DistantLightCfg(),
+    )
+
+
+class TestInteractiveScene(unittest.TestCase):
+    """Test cases for InteractiveScene."""
+
+    def setUp(self) -> None:
+        self.devices = ["cuda:0", "cpu"]
+        self.sim_dt = 0.001
+        self.scene_cfg = MySceneCfg(num_envs=1, env_spacing=1)
+
+    def test_scene_entity_isolation(self):
+        """Tests that multiple instances of InteractiveScene does not share any data.
+
+        In this test, two InteractiveScene instances are created in a loop and added to a list.
+        The scene at index 0 of the list will have all of its entities cleared manually, and
+        the test compares that the data held in the scene at index 1 remained intact.
+        """
+        for device in self.devices:
+            scene_list = []
+            # create two InteractiveScene instances
+            for _ in range(2):
+                with build_simulation_context(device=device, dt=self.sim_dt) as _:
+                    scene = InteractiveScene(MySceneCfg(num_envs=1, env_spacing=1))
+                    scene_list.append(scene)
+            scene_0 = scene_list[0]
+            scene_1 = scene_list[1]
+            # clear entities for scene_0 - this should not affect any data in scene_1
+            scene_0.articulations.clear()
+            scene_0.rigid_objects.clear()
+            scene_0.sensors.clear()
+            scene_0.extras.clear()
+            # check that scene_0 and scene_1 do not share entity data via dictionary comparison
+            self.assertEqual(scene_0.articulations, dict())
+            self.assertNotEqual(scene_0.articulations, scene_1.articulations)
+            self.assertEqual(scene_0.rigid_objects, dict())
+            self.assertNotEqual(scene_0.rigid_objects, scene_1.rigid_objects)
+            self.assertEqual(scene_0.sensors, dict())
+            self.assertNotEqual(scene_0.sensors, scene_1.sensors)
+            self.assertEqual(scene_0.extras, dict())
+            self.assertNotEqual(scene_0.extras, scene_1.extras)
+
+
+if __name__ == "__main__":
+
+    # run main
+    unittest.main(verbosity=2, exit=False)
+    # close sim app
+    simulation_app.close()