Fixes contact threshold when activating contact sensor (#3498)

# Description

We were incorrectly passing in the activate contact sensor boolean as
the threshold when setting up the contact sensor API, which caused the
sensor threshold to always be 1 when the sensor is activated. The
desired behavior should be defaulting to 0 threshold.


## Type of change

- Bug fix (non-breaking change which fixes an issue)
- Breaking change (existing functionality will not work without user
modification)

## Checklist

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.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
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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---------

Signed-off-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>
Signed-off-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>

Author: kellyguo11

source/isaaclab/config/extension.toml

@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.47.11"
+version = "0.48.0"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/isaaclab/docs/CHANGELOG.rst

@@ -1,6 +1,22 @@
 Changelog
 ---------
 
+0.48.0 (2025-11-03)
+~~~~~~~~~~~~~~~~~~~
+
+Changed
+^^^^^^^
+
+* Detected contacts are reported with the threshold of 0.0 (instead of 1.0). This increases the sensitivity of contact
+  detection.
+
+Fixed
+^^^^^
+
+* Removed passing the boolean flag to :meth:`isaaclab.sim.schemas.activate_contact_sensors` when activating contact
+  sensors. This was incorrectly modifying the threshold attribute to 1.0 when contact sensors were activated.
+
+
 0.47.11 (2025-11-03)
 ~~~~~~~~~~~~~~~~~~~~
 
@@ -95,8 +111,8 @@ Changed
 0.47.3 (2025-10-22)
 ~~~~~~~~~~~~~~~~~~~
 
-Changed
-^^^^^^^
+Fixed
+^^^^^
 
 * Fixed the data type conversion in :class:`~isaaclab.sensors.tiled_camera.TiledCamera` to
   support the correct data type when converting from numpy arrays to warp arrays on the CPU.

source/isaaclab/isaaclab/sim/utils.py

@@ -288,7 +288,7 @@ def wrapper(prim_path: str | Sdf.Path, cfg: SpawnerCfg, *args, **kwargs):
                 sem.GetSemanticDataAttr().Set(semantic_value)
         # activate rigid body contact sensors
         if hasattr(cfg, "activate_contact_sensors") and cfg.activate_contact_sensors:
-            schemas.activate_contact_sensors(prim_paths[0], cfg.activate_contact_sensors)
+            schemas.activate_contact_sensors(prim_paths[0])
         # clone asset using cloner API
         if len(prim_paths) > 1:
             cloner = Cloner(stage=stage)

source/isaaclab/test/sensors/test_contact_sensor.py

@@ -21,6 +21,7 @@
 import carb
 import pytest
 from flaky import flaky
+from pxr import PhysxSchema
 
 import isaaclab.sim as sim_utils
 from isaaclab.assets import RigidObject, RigidObjectCfg
@@ -395,6 +396,50 @@ def test_sensor_print(setup_simulation):
         print(scene.sensors["contact_sensor"])
 
 
+@pytest.mark.parametrize("device", ["cuda:0", "cpu"])
+def test_contact_sensor_threshold(setup_simulation, device):
+    """Test that the contact sensor USD threshold attribute is set to 0.0."""
+    sim_dt, durations, terrains, devices, carb_settings_iface = setup_simulation
+    with build_simulation_context(device=device, dt=sim_dt, add_lighting=False) as sim:
+        sim._app_control_on_stop_handle = None
+        # Spawn things into stage
+        scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
+        scene_cfg.terrain = FLAT_TERRAIN_CFG.replace(prim_path="/World/ground")
+        scene_cfg.shape = CUBE_CFG
+        scene_cfg.contact_sensor = ContactSensorCfg(
+            prim_path=scene_cfg.shape.prim_path,
+            track_pose=True,
+            debug_vis=False,
+            update_period=0.0,
+            track_air_time=True,
+            history_length=3,
+        )
+        scene = InteractiveScene(scene_cfg)
+        # Play the simulator
+        sim.reset()
+
+        # Get the stage and check the USD threshold attribute on the rigid body prim
+        from isaacsim.core.utils.stage import get_current_stage
+
+        stage = get_current_stage()
+        prim_path = scene_cfg.shape.prim_path
+        prim = stage.GetPrimAtPath(prim_path)
+
+        # Ensure the contact sensor was created properly
+        contact_sensor = scene["contact_sensor"]
+        assert contact_sensor is not None, "Contact sensor was not created"
+
+        # Check if the prim has contact report API and verify threshold is close to 0.0
+        if prim.HasAPI(PhysxSchema.PhysxContactReportAPI):
+            cr_api = PhysxSchema.PhysxContactReportAPI.Get(stage, prim.GetPrimPath())
+            threshold_attr = cr_api.GetThresholdAttr()
+            if threshold_attr.IsValid():
+                threshold_value = threshold_attr.Get()
+                assert (
+                    pytest.approx(threshold_value, abs=1e-6) == 0.0
+                ), f"Expected USD threshold to be close to 0.0, but got {threshold_value}"
+
+
 """
 Internal helpers.
 """