From 1e1e6e0293f022af96403b030458f61d3981f821 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 24 Sep 2025 14:50:07 -0400
Subject: [PATCH 01/33] removed redundant buffer

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index aed50d390f8..af6f078011c 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -162,8 +162,6 @@ def reset(self, env_ids: Sequence[int] | None = None):
         # reset contact positions
         if self.cfg.track_contact_points:
             self._data.contact_pos_w[env_ids, :] = torch.nan
-            # buffer used during contact position aggregation
-            self._contact_position_aggregate_buffer[env_ids, :] = torch.nan
 
     def find_bodies(self, name_keys: str | Sequence[str], preserve_order: bool = False) -> tuple[list[int], list[str]]:
         """Find bodies in the articulation based on the name keys.
@@ -317,12 +315,6 @@ def _initialize_impl(self):
                 torch.nan,
                 device=self._device,
             )
-            # buffer used during contact position aggregation
-            self._contact_position_aggregate_buffer = torch.full(
-                (self._num_bodies * self._num_envs, self.contact_physx_view.filter_count, 3),
-                torch.nan,
-                device=self._device,
-            )
         # -- air/contact time between contacts
         if self.cfg.track_air_time:
             self._data.last_air_time = torch.zeros(self._num_envs, self._num_bodies, device=self._device)
@@ -401,8 +393,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 agg = agg.zero_().index_add_(0, row_ids, pts) / counts.clamp_min(1).unsqueeze(1)
                 agg[counts == 0] = float("nan")
 
-            self._contact_position_aggregate_buffer[:] = agg.view(self._num_envs * self.num_bodies, -1, 3)
-            self._data.contact_pos_w[env_ids] = self._contact_position_aggregate_buffer.view(
+            self._data.contact_pos_w[env_ids] = agg.view(self._num_envs * self.num_bodies, -1, 3).view(
                 self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3
             )[env_ids]
 

From e9c9f47a0053e24c79711535db10459f729b409c Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 24 Sep 2025 15:18:58 -0400
Subject: [PATCH 02/33] added friction force tracking

---
 .../sensors/contact_sensor/contact_sensor.py  | 36 +++++++++++++++----
 .../contact_sensor/contact_sensor_cfg.py      |  3 ++
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index af6f078011c..96b369047a9 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -162,6 +162,9 @@ def reset(self, env_ids: Sequence[int] | None = None):
         # reset contact positions
         if self.cfg.track_contact_points:
             self._data.contact_pos_w[env_ids, :] = torch.nan
+        # reset friction forces
+        if self.cfg.track_friction_forces:
+            self._data.friction_forces_w[env_ids, :] = torch.nan
 
     def find_bodies(self, name_keys: str | Sequence[str], preserve_order: bool = False) -> tuple[list[int], list[str]]:
         """Find bodies in the articulation based on the name keys.
@@ -315,6 +318,13 @@ def _initialize_impl(self):
                 torch.nan,
                 device=self._device,
             )
+        # -- friction forces at contact points
+        if self.cfg.track_friction_forces:
+            self._data.friction_forces_w = torch.full(
+                (self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3),
+                torch.nan,
+                device=self._device,
+            )
         # -- air/contact time between contacts
         if self.cfg.track_air_time:
             self._data.last_air_time = torch.zeros(self._num_envs, self._num_bodies, device=self._device)
@@ -369,11 +379,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             pose[..., 3:] = convert_quat(pose[..., 3:], to="wxyz")
             self._data.pos_w[env_ids], self._data.quat_w[env_ids] = pose.split([3, 4], dim=-1)
 
-        # obtain contact points
-        if self.cfg.track_contact_points:
-            _, buffer_contact_points, _, _, buffer_count, buffer_start_indices = (
-                self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
-            )
+        def unpack_contact_points(contact_points, buffer_count, buffer_start_indices):
             # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
             # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
             # buffer_count: (N_envs * N_bodies, N_filters), buffer_contact_points: (N_envs * N_bodies, 3)
@@ -393,9 +399,25 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 agg = agg.zero_().index_add_(0, row_ids, pts) / counts.clamp_min(1).unsqueeze(1)
                 agg[counts == 0] = float("nan")
 
-            self._data.contact_pos_w[env_ids] = agg.view(self._num_envs * self.num_bodies, -1, 3).view(
+            return agg.view(self._num_envs * self.num_bodies, -1, 3).view(
                 self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3
-            )[env_ids]
+            )
+
+        # obtain contact points
+        if self.cfg.track_contact_points:
+            _, buffer_contact_points, _, _, buffer_count, buffer_start_indices = (
+                self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
+            )
+            self._data.contact_pos_w[env_ids] = unpack_contact_points(
+                buffer_contact_points, buffer_count, buffer_start_indices)[env_ids]
+
+        # obtain friction forces
+        if self.cfg.track_friction_forces:
+            friction_forces, buffer_count, buffer_start_indices = (
+                self.contact_physx_view.get_friction_forces(dt=self._sim_physics_dt)
+            )
+            self._data.friction_forces_w[env_ids] = unpack_contact_points(
+                friction_forces, buffer_count, buffer_start_indices)[env_ids]
 
         # obtain the air time
         if self.cfg.track_air_time:
diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_cfg.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_cfg.py
index c51b09473bb..e230b9fd2be 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_cfg.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_cfg.py
@@ -23,6 +23,9 @@ class ContactSensorCfg(SensorBaseCfg):
     track_contact_points: bool = False
     """Whether to track the contact point locations. Defaults to False."""
 
+    track_friction_forces: bool = False
+    """Whether to track the friction forces at the contact points. Defaults to False."""
+
     max_contact_data_count_per_prim: int = 4
     """The maximum number of contacts across all batches of the sensor to keep track of. Default is 4.
 

From e2a9f4374d161ca015af7b9dd8ef7afa32ddf332 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 24 Sep 2025 15:25:38 -0400
Subject: [PATCH 03/33] added friction force shape test

---
 .../contact_sensor/contact_sensor_data.py     | 15 +++++
 .../test/sensors/test_contact_sensor.py       | 56 ++++++++++++-------
 2 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
index 5d08f6058ce..8a1c6c2947c 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
@@ -38,7 +38,22 @@ class ContactSensorData:
         * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty, then this quantity is an empty tensor.
         * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1, then this quantity
           will not be calculated.
+    """
+
+    friction_forces_w: torch.Tensor | None = None
+    """Average of the friction forces between sensor body and filter prim in world frame.
+
+    Shape is (N, B, M, 3), where N is the number of sensors, B is number of bodies in each sensor
+    and M is the number of filtered bodies.
+
+    Collision pairs not in contact will result in NaN.
+
+    Note:
 
+        * If the :attr:`ContactSensorCfg.track_friction_forces` is False, then this quantity is None.
+        * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty, then this quantity is an empty tensor.
+        * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1, then this quantity
+          will not be calculated.
     """
 
     quat_w: torch.Tensor | None = None
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index c30a7d2eaf1..a9e405c0c15 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -422,9 +422,9 @@ def _run_contact_sensor_test(
                     scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
                     scene_cfg.terrain = terrain
                     scene_cfg.shape = shape_cfg
-                    test_contact_position = False
+                    test_contact_data = False
                     if (type(shape_cfg.spawn) is sim_utils.SphereCfg) and (terrain.terrain_type == "plane"):
-                        test_contact_position = True
+                        test_contact_data = True
                     elif track_contact_points:
                         continue
 
@@ -460,7 +460,7 @@ def _run_contact_sensor_test(
                         scene=scene,
                         sim_dt=sim_dt,
                         durations=durations,
-                        test_contact_position=test_contact_position,
+                        test_contact_data=test_contact_data,
                     )
                     _test_sensor_contact(
                         shape=scene["shape"],
@@ -470,7 +470,7 @@ def _run_contact_sensor_test(
                         scene=scene,
                         sim_dt=sim_dt,
                         durations=durations,
-                        test_contact_position=test_contact_position,
+                        test_contact_data=test_contact_data,
                     )
 
 
@@ -482,7 +482,7 @@ def _test_sensor_contact(
     scene: InteractiveScene,
     sim_dt: float,
     durations: list[float],
-    test_contact_position: bool = False,
+    test_contact_data: bool = False,
 ):
     """Test for the contact sensor.
 
@@ -549,8 +549,11 @@ def _test_sensor_contact(
                 expected_last_air_time=expected_last_test_contact_time,
                 dt=duration + sim_dt,
             )
-        if test_contact_position:
+
+        if test_contact_data:
             _test_contact_position(shape, sensor, mode)
+            _test_contact_forces(shape, sensor, mode)
+
         # switch the contact mode for 1 dt step before the next contact test begins.
         shape.write_root_pose_to_sim(root_pose=reset_pose)
         # perform simulation step
@@ -561,6 +564,16 @@ def _test_sensor_contact(
         expected_last_reset_contact_time = 2 * sim_dt
 
 
+def _test_contact_forces(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:
+    if not sensor.cfg.track_friction_forces:
+        assert sensor._data.friction_forces_w is None
+        return
+
+    # check shape of the contact_pos_w tensor
+    num_bodies = sensor.num_bodies
+    assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
+
+
 def _test_contact_position(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:
     """Test for the contact positions (only implemented for sphere and flat terrain)
     checks that the contact position is radius distance away from the root of the object
@@ -569,22 +582,23 @@ def _test_contact_position(shape: RigidObject, sensor: ContactSensor, mode: Cont
         sensor: The sensor reporting data to be verified by the contact sensor test.
         mode: The contact test mode: either contact with ground plane or air time.
     """
-    if sensor.cfg.track_contact_points:
-        # check shape of the contact_pos_w tensor
-        num_bodies = sensor.num_bodies
-        assert sensor._data.contact_pos_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
-        # check contact positions
-        if mode == ContactTestMode.IN_CONTACT:
-            contact_position = sensor._data.pos_w + torch.tensor(
-                [[0.0, 0.0, -shape.cfg.spawn.radius]], device=sensor._data.pos_w.device
-            )
-            assert torch.all(
-                torch.abs(torch.norm(sensor._data.contact_pos_w - contact_position.unsqueeze(1), p=2, dim=-1)) < 1e-2
-            ).item()
-        elif mode == ContactTestMode.NON_CONTACT:
-            assert torch.all(torch.isnan(sensor._data.contact_pos_w)).item()
-    else:
+    if not sensor.cfg.track_contact_points:
         assert sensor._data.contact_pos_w is None
+        return
+
+    # check shape of the contact_pos_w tensor
+    num_bodies = sensor.num_bodies
+    assert sensor._data.contact_pos_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
+    # check contact positions
+    if mode == ContactTestMode.IN_CONTACT:
+        contact_position = sensor._data.pos_w + torch.tensor(
+            [[0.0, 0.0, -shape.cfg.spawn.radius]], device=sensor._data.pos_w.device
+        )
+        assert torch.all(
+            torch.abs(torch.norm(sensor._data.contact_pos_w - contact_position.unsqueeze(1), p=2, dim=-1)) < 1e-2
+        ).item()
+    elif mode == ContactTestMode.NON_CONTACT:
+        assert torch.all(torch.isnan(sensor._data.contact_pos_w)).item()
 
 
 def _check_prim_contact_state_times(

From ac32441254f799bb5ff54bff0c16efc7f5a92a07 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 24 Sep 2025 15:27:40 -0400
Subject: [PATCH 04/33] added non contact test

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index a9e405c0c15..6d77ffbc824 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -552,7 +552,7 @@ def _test_sensor_contact(
 
         if test_contact_data:
             _test_contact_position(shape, sensor, mode)
-            _test_contact_forces(shape, sensor, mode)
+            _test_friction_forces(shape, sensor, mode)
 
         # switch the contact mode for 1 dt step before the next contact test begins.
         shape.write_root_pose_to_sim(root_pose=reset_pose)
@@ -564,7 +564,7 @@ def _test_sensor_contact(
         expected_last_reset_contact_time = 2 * sim_dt
 
 
-def _test_contact_forces(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:
+def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:
     if not sensor.cfg.track_friction_forces:
         assert sensor._data.friction_forces_w is None
         return
@@ -572,6 +572,11 @@ def _test_contact_forces(shape: RigidObject, sensor: ContactSensor, mode: Contac
     # check shape of the contact_pos_w tensor
     num_bodies = sensor.num_bodies
     assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
+    # check friction forces
+    if mode == ContactTestMode.IN_CONTACT:
+        pass
+    elif mode == ContactTestMode.NON_CONTACT:
+        assert torch.all(torch.isnan(sensor._data.friction_forces_w)).item()
 
 
 def _test_contact_position(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:

From 1aad6c1434e90d4de7c63b60cf4a66cc31d884a4 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 09:39:57 -0400
Subject: [PATCH 05/33] validating non nan

---
 .../sensors/contact_sensor/contact_sensor.py  | 59 ++++++++++---------
 .../test/sensors/test_contact_sensor.py       | 11 ++--
 2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 96b369047a9..665015dabc3 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -379,45 +379,21 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             pose[..., 3:] = convert_quat(pose[..., 3:], to="wxyz")
             self._data.pos_w[env_ids], self._data.quat_w[env_ids] = pose.split([3, 4], dim=-1)
 
-        def unpack_contact_points(contact_points, buffer_count, buffer_start_indices):
-            # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
-            # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
-            # buffer_count: (N_envs * N_bodies, N_filters), buffer_contact_points: (N_envs * N_bodies, 3)
-            counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
-            n_rows, total = counts.numel(), int(counts.sum())
-            # default to NaN rows
-            agg = torch.full((n_rows, 3), float("nan"), device=self._device, dtype=buffer_contact_points.dtype)
-            if total > 0:
-                row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)
-                total = row_ids.numel()
-
-                block_starts = counts.cumsum(0) - counts
-                deltas = torch.arange(total, device=counts.device) - block_starts.repeat_interleave(counts)
-                flat_idx = starts[row_ids] + deltas
-
-                pts = buffer_contact_points.index_select(0, flat_idx)
-                agg = agg.zero_().index_add_(0, row_ids, pts) / counts.clamp_min(1).unsqueeze(1)
-                agg[counts == 0] = float("nan")
-
-            return agg.view(self._num_envs * self.num_bodies, -1, 3).view(
-                self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3
-            )
-
         # obtain contact points
         if self.cfg.track_contact_points:
             _, buffer_contact_points, _, _, buffer_count, buffer_start_indices = (
                 self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
             )
-            self._data.contact_pos_w[env_ids] = unpack_contact_points(
+            self._data.contact_pos_w[env_ids] = self._unpack_contact_points(
                 buffer_contact_points, buffer_count, buffer_start_indices)[env_ids]
 
         # obtain friction forces
         if self.cfg.track_friction_forces:
-            friction_forces, buffer_count, buffer_start_indices = (
-                self.contact_physx_view.get_friction_forces(dt=self._sim_physics_dt)
+            friction_forces, _, buffer_count, buffer_start_indices = (
+                self.contact_physx_view.get_friction_data(dt=self._sim_physics_dt)
             )
-            self._data.friction_forces_w[env_ids] = unpack_contact_points(
-                friction_forces, buffer_count, buffer_start_indices)[env_ids]
+            self._data.friction_forces_w[env_ids] = self._unpack_contact_points(
+                friction_forces, buffer_count, buffer_start_indices, avg=False)[env_ids]
 
         # obtain the air time
         if self.cfg.track_air_time:
@@ -449,6 +425,31 @@ def unpack_contact_points(contact_points, buffer_count, buffer_start_indices):
                 is_contact, self._data.current_contact_time[env_ids] + elapsed_time.unsqueeze(-1), 0.0
             )
 
+    def _unpack_contact_points(self, contact_points, buffer_count, buffer_start_indices, avg=True):
+        # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
+        # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
+        # buffer_count: (N_envs * N_bodies, N_filters), contact_points: (N_envs * N_bodies, 3)
+        counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
+        n_rows, total = counts.numel(), int(counts.sum())
+        # default to NaN rows
+        agg = torch.full((n_rows, 3), float("nan"), device=self._device, dtype=contact_points.dtype)
+        if total > 0:
+            row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)
+            total = row_ids.numel()
+
+            block_starts = counts.cumsum(0) - counts
+            deltas = torch.arange(total, device=counts.device) - block_starts.repeat_interleave(counts)
+            flat_idx = starts[row_ids] + deltas
+
+            pts = contact_points.index_select(0, flat_idx)
+            agg = agg.zero_().index_add_(0, row_ids, pts)
+            agg = agg / counts.unsqueeze(-1) if avg else agg
+            agg[counts == 0] = float("nan")
+
+        return agg.view(self._num_envs * self.num_bodies, -1, 3).view(
+            self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3
+        )
+
     def _set_debug_vis_impl(self, debug_vis: bool):
         # set visibility of markers
         # note: parent only deals with callbacks. not their visibility
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 6d77ffbc824..c17a1faf4da 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -415,7 +415,7 @@ def _run_contact_sensor_test(
     """
     for device in devices:
         for terrain in terrains:
-            for track_contact_points in [True, False]:
+            for track_contact_data in [True, False]:
                 with build_simulation_context(device=device, dt=sim_dt, add_lighting=True) as sim:
                     sim._app_control_on_stop_handle = None
 
@@ -425,10 +425,10 @@ def _run_contact_sensor_test(
                     test_contact_data = False
                     if (type(shape_cfg.spawn) is sim_utils.SphereCfg) and (terrain.terrain_type == "plane"):
                         test_contact_data = True
-                    elif track_contact_points:
+                    elif track_contact_data:
                         continue
 
-                    if track_contact_points:
+                    if track_contact_data:
                         if terrain.terrain_type == "plane":
                             filter_prim_paths_expr = [terrain.prim_path + "/terrain/GroundPlane/CollisionPlane"]
                         elif terrain.terrain_type == "generator":
@@ -443,7 +443,8 @@ def _run_contact_sensor_test(
                         update_period=0.0,
                         track_air_time=True,
                         history_length=3,
-                        track_contact_points=track_contact_points,
+                        track_contact_points=track_contact_data,
+                        track_friction_forces=track_contact_data,
                         filter_prim_paths_expr=filter_prim_paths_expr,
                     )
                     scene = InteractiveScene(scene_cfg)
@@ -574,7 +575,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
     # check friction forces
     if mode == ContactTestMode.IN_CONTACT:
-        pass
+        assert not torch.any(torch.isnan(sensor._data.friction_forces_w)).item()
     elif mode == ContactTestMode.NON_CONTACT:
         assert torch.all(torch.isnan(sensor._data.friction_forces_w)).item()
 

From fa22e4016e54d89c39e88198a7a603040337617b Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 10:36:23 -0400
Subject: [PATCH 06/33] test to validate vectorized solution

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py  | 10 ++++++++++
 source/isaaclab/test/sensors/test_contact_sensor.py    | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 665015dabc3..4c46f2d4481 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -429,6 +429,16 @@ def _unpack_contact_points(self, contact_points, buffer_count, buffer_start_indi
         # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
         # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
         # buffer_count: (N_envs * N_bodies, N_filters), contact_points: (N_envs * N_bodies, 3)
+        """
+        Vectorizes the following nested loop:
+        for i in range(self._num_bodies * self._num_envs):
+            for j in range(self.contact_physx_view.filter_count):
+                start_index_ij = buffer_start_indices[i, j]
+                count_ij = buffer_count[i, j]
+                self._contact_position_aggregate_buffer[i, j, :] = torch.mean(
+                    contact_points[start_index_ij : (start_index_ij + count_ij), :], dim=0
+                )
+        """
         counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
         n_rows, total = counts.numel(), int(counts.sum())
         # default to NaN rows
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index c17a1faf4da..7fc6c77018f 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -576,6 +576,16 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     # check friction forces
     if mode == ContactTestMode.IN_CONTACT:
         assert not torch.any(torch.isnan(sensor._data.friction_forces_w)).item()
+        friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(dt=sensor._sim_physics_dt)
+        for i in range(sensor.num_instances * num_bodies):
+            for j in range(sensor.contact_physx_view.filter_count):
+                start_index_ij = buffer_start_indices[i, j]
+                count_ij = buffer_count[i, j]
+                force = torch.sum(
+                    friction_forces[start_index_ij : (start_index_ij + count_ij), :], dim=0
+                )
+                assert torch.allclose(force, sensor._data.friction_forces_w[i, j, :], atol=1e-5)
+
     elif mode == ContactTestMode.NON_CONTACT:
         assert torch.all(torch.isnan(sensor._data.friction_forces_w)).item()
 

From 0e4f6d4272dfe073034c6bcb3da4edb91cbfe692 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 11:26:52 -0400
Subject: [PATCH 07/33] formatting

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py  | 10 ++++++----
 source/isaaclab/test/sensors/test_contact_sensor.py    |  8 ++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 4c46f2d4481..415cdd021e4 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -385,15 +385,17 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
             )
             self._data.contact_pos_w[env_ids] = self._unpack_contact_points(
-                buffer_contact_points, buffer_count, buffer_start_indices)[env_ids]
+                buffer_contact_points, buffer_count, buffer_start_indices
+            )[env_ids]
 
         # obtain friction forces
         if self.cfg.track_friction_forces:
-            friction_forces, _, buffer_count, buffer_start_indices = (
-                self.contact_physx_view.get_friction_data(dt=self._sim_physics_dt)
+            friction_forces, _, buffer_count, buffer_start_indices = self.contact_physx_view.get_friction_data(
+                dt=self._sim_physics_dt
             )
             self._data.friction_forces_w[env_ids] = self._unpack_contact_points(
-                friction_forces, buffer_count, buffer_start_indices, avg=False)[env_ids]
+                friction_forces, buffer_count, buffer_start_indices, avg=False
+            )[env_ids]
 
         # obtain the air time
         if self.cfg.track_air_time:
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 7fc6c77018f..8f2c3e11b43 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -576,14 +576,14 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     # check friction forces
     if mode == ContactTestMode.IN_CONTACT:
         assert not torch.any(torch.isnan(sensor._data.friction_forces_w)).item()
-        friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(dt=sensor._sim_physics_dt)
+        friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(
+            dt=sensor._sim_physics_dt
+        )
         for i in range(sensor.num_instances * num_bodies):
             for j in range(sensor.contact_physx_view.filter_count):
                 start_index_ij = buffer_start_indices[i, j]
                 count_ij = buffer_count[i, j]
-                force = torch.sum(
-                    friction_forces[start_index_ij : (start_index_ij + count_ij), :], dim=0
-                )
+                force = torch.sum(friction_forces[start_index_ij : (start_index_ij + count_ij), :], dim=0)
                 assert torch.allclose(force, sensor._data.friction_forces_w[i, j, :], atol=1e-5)
 
     elif mode == ContactTestMode.NON_CONTACT:

From c78c80c627e6df4f5b0675257371522dc79d346d Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 11:34:27 -0400
Subject: [PATCH 08/33] updating doc / version

---
 source/isaaclab/config/extension.toml                | 2 +-
 source/isaaclab/docs/CHANGELOG.rst                   | 8 ++++++++
 source/isaaclab/test/sensors/check_contact_sensor.py | 1 +
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/source/isaaclab/config/extension.toml b/source/isaaclab/config/extension.toml
index d2c0e84fecd..cbc2de67560 100644
--- a/source/isaaclab/config/extension.toml
+++ b/source/isaaclab/config/extension.toml
@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.47.1"
+version = "0.47.2"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"
diff --git a/source/isaaclab/docs/CHANGELOG.rst b/source/isaaclab/docs/CHANGELOG.rst
index eb33e88773f..e625b2470af 100644
--- a/source/isaaclab/docs/CHANGELOG.rst
+++ b/source/isaaclab/docs/CHANGELOG.rst
@@ -1,6 +1,14 @@
 Changelog
 ---------
 
+0.47.2 (2025-10-20)
+~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+* Added :attr:`~isaaclab.sensors.contact_sensor.ContactSensorCfg.track_friction_forces` to toggle tracking of friction forces between sensor bodies and filtered bodies.
+* Added :attr:`~isaaclab.sensors.contact_sensor.ContactSensorData.friction_forces_w` data field for tracking friction forces.
+
 0.47.1 (2025-10-17)
 ~~~~~~~~~~~~~~~~~~~
 
diff --git a/source/isaaclab/test/sensors/check_contact_sensor.py b/source/isaaclab/test/sensors/check_contact_sensor.py
index 30d2c9be437..431ab2f47f6 100644
--- a/source/isaaclab/test/sensors/check_contact_sensor.py
+++ b/source/isaaclab/test/sensors/check_contact_sensor.py
@@ -106,6 +106,7 @@ def main():
         prim_path="/World/envs/env_.*/Robot/.*_FOOT",
         track_air_time=True,
         track_contact_points=True,
+        track_friction_forces=True,
         debug_vis=False,  # not args_cli.headless,
         filter_prim_paths_expr=["/World/defaultGroundPlane/GroundPlane/CollisionPlane"],
     )

From ab095a94d2533f8131b4d4cbac6c7918041618c0 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 11:43:09 -0400
Subject: [PATCH 09/33] rename func to be more generic

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py  | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 415cdd021e4..7da37c192a2 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -384,7 +384,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             _, buffer_contact_points, _, _, buffer_count, buffer_start_indices = (
                 self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
             )
-            self._data.contact_pos_w[env_ids] = self._unpack_contact_points(
+            self._data.contact_pos_w[env_ids] = self._unpack_contact_data(
                 buffer_contact_points, buffer_count, buffer_start_indices
             )[env_ids]
 
@@ -393,7 +393,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             friction_forces, _, buffer_count, buffer_start_indices = self.contact_physx_view.get_friction_data(
                 dt=self._sim_physics_dt
             )
-            self._data.friction_forces_w[env_ids] = self._unpack_contact_points(
+            self._data.friction_forces_w[env_ids] = self._unpack_contact_data(
                 friction_forces, buffer_count, buffer_start_indices, avg=False
             )[env_ids]
 
@@ -427,7 +427,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 is_contact, self._data.current_contact_time[env_ids] + elapsed_time.unsqueeze(-1), 0.0
             )
 
-    def _unpack_contact_points(self, contact_points, buffer_count, buffer_start_indices, avg=True):
+    def _unpack_contact_data(self, contact_data, buffer_count, buffer_start_indices, avg=True):
         # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
         # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
         # buffer_count: (N_envs * N_bodies, N_filters), contact_points: (N_envs * N_bodies, 3)
@@ -444,7 +444,7 @@ def _unpack_contact_points(self, contact_points, buffer_count, buffer_start_indi
         counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
         n_rows, total = counts.numel(), int(counts.sum())
         # default to NaN rows
-        agg = torch.full((n_rows, 3), float("nan"), device=self._device, dtype=contact_points.dtype)
+        agg = torch.full((n_rows, 3), float("nan"), device=self._device, dtype=contact_data.dtype)
         if total > 0:
             row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)
             total = row_ids.numel()
@@ -453,7 +453,7 @@ def _unpack_contact_points(self, contact_points, buffer_count, buffer_start_indi
             deltas = torch.arange(total, device=counts.device) - block_starts.repeat_interleave(counts)
             flat_idx = starts[row_ids] + deltas
 
-            pts = contact_points.index_select(0, flat_idx)
+            pts = contact_data.index_select(0, flat_idx)
             agg = agg.zero_().index_add_(0, row_ids, pts)
             agg = agg / counts.unsqueeze(-1) if avg else agg
             agg[counts == 0] = float("nan")

From eee482276ef5133d46acc366661203c48e253177 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 11:48:10 -0400
Subject: [PATCH 10/33] added to contributors

---
 CONTRIBUTORS.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 0feaabb2c8f..e99eb97144c 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -35,6 +35,7 @@ Guidelines for modifications:
 * Pascal Roth
 * Sheikh Dawood
 * Ossama Ahmed
+* Greg Attra
 
 ## Contributors
 

From 664056b0bb0d655f4fa1eb31624482b76bf4d490 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 16:11:16 -0400
Subject: [PATCH 11/33] test to check that friction forces make sense

---
 .../test/sensors/check_contact_sensor.py      |  2 +-
 .../test/sensors/test_contact_sensor.py       | 61 ++++++++++++++++++-
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/test/sensors/check_contact_sensor.py b/source/isaaclab/test/sensors/check_contact_sensor.py
index 431ab2f47f6..32c628d7024 100644
--- a/source/isaaclab/test/sensors/check_contact_sensor.py
+++ b/source/isaaclab/test/sensors/check_contact_sensor.py
@@ -106,7 +106,7 @@ def main():
         prim_path="/World/envs/env_.*/Robot/.*_FOOT",
         track_air_time=True,
         track_contact_points=True,
-        track_friction_forces=True,
+        # track_friction_forces=True,
         debug_vis=False,  # not args_cli.headless,
         filter_prim_paths_expr=["/World/defaultGroundPlane/GroundPlane/CollisionPlane"],
     )
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 8f2c3e11b43..b01d1ed5856 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -30,6 +30,8 @@
 from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg
 from isaaclab.utils import configclass
 
+from pxr import Gf, UsdPhysics
+
 ##
 # Custom helper classes.
 ##
@@ -394,6 +396,63 @@ def test_sensor_print(setup_simulation):
         print(scene.sensors["contact_sensor"])
 
 
+@pytest.mark.parametrize("grav_dir", [(-10.0, 0.0, -1.0), (0.0, -10.0, -1.0)])
+@pytest.mark.isaacsim_ci
+def test_friction_reporting(setup_simulation, grav_dir):
+    """
+    Test friction force reporting for contact sensors.
+
+    This test places a contact sensor enabled cube onto a ground plane under different gravity directions.
+    It then compares the normalized friction force dir with the direction of gravity to ensure they are aligned.
+    """
+    sim_dt, _, _, _, carb_settings_iface = setup_simulation
+    carb_settings_iface.set_bool("/physics/disableContactProcessing", True)
+    device = "cuda:0"
+    with build_simulation_context(device=device, dt=sim_dt, add_lighting=False) as sim:
+        sim._app_control_on_stop_handle = None
+
+        scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
+        scene_cfg.terrain = FLAT_TERRAIN_CFG
+        scene_cfg.shape = CUBE_CFG
+
+        filter_prim_paths_expr = [scene_cfg.terrain.prim_path + "/terrain/GroundPlane/CollisionPlane"]
+
+        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,
+            track_friction_forces=True,
+            filter_prim_paths_expr=filter_prim_paths_expr)
+
+        scene = InteractiveScene(scene_cfg)
+
+        # set custom gravity
+        UsdPhysics.Scene.Get(scene.stage, "/physicsScene").CreateGravityDirectionAttr().Set(Gf.Vec3f(*grav_dir))
+
+        sim.reset()
+
+        scene["contact_sensor"].reset()
+        scene["shape"].write_root_pose_to_sim(root_pose=torch.tensor([0, 0.0, CUBE_CFG.spawn.size[2] / 2.0, 1, 0, 0, 0]))
+
+        # step sim once to compute friction forces
+        _perform_sim_step(sim, scene, sim_dt)
+
+        friction_force = scene["contact_sensor"]._data.friction_forces_w[0, 0, :]
+        friction_magnitude = friction_force.norm().item()
+
+        assert friction_magnitude > 1e-6, "Friction forces should be non-zero"
+
+        grav = torch.tensor(grav_dir, device=device)
+        norm_friction = friction_force / friction_force.norm()
+        norm_gravity = grav / grav.norm()
+        dot = torch.dot(norm_friction.squeeze(), norm_gravity)
+
+        assert torch.isclose(torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-2), "Friction force should be roughly opposite gravity direction"
+
+
 """
 Internal helpers.
 """
@@ -573,7 +632,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     # check shape of the contact_pos_w tensor
     num_bodies = sensor.num_bodies
     assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
-    # check friction forces
+    # compare friction forces
     if mode == ContactTestMode.IN_CONTACT:
         assert not torch.any(torch.isnan(sensor._data.friction_forces_w)).item()
         friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(

From 30a7b5d0dbe4628bfcd5743020250efbe5a5628b Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 16:12:25 -0400
Subject: [PATCH 12/33] formatting

---
 .../isaaclab/test/sensors/test_contact_sensor.py | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index b01d1ed5856..361ad943239 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -21,6 +21,7 @@
 import carb
 import pytest
 from flaky import flaky
+from pxr import Gf, UsdPhysics
 
 import isaaclab.sim as sim_utils
 from isaaclab.assets import RigidObject, RigidObjectCfg
@@ -30,8 +31,6 @@
 from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg
 from isaaclab.utils import configclass
 
-from pxr import Gf, UsdPhysics
-
 ##
 # Custom helper classes.
 ##
@@ -425,7 +424,8 @@ def test_friction_reporting(setup_simulation, grav_dir):
             track_air_time=True,
             history_length=3,
             track_friction_forces=True,
-            filter_prim_paths_expr=filter_prim_paths_expr)
+            filter_prim_paths_expr=filter_prim_paths_expr,
+        )
 
         scene = InteractiveScene(scene_cfg)
 
@@ -435,7 +435,9 @@ def test_friction_reporting(setup_simulation, grav_dir):
         sim.reset()
 
         scene["contact_sensor"].reset()
-        scene["shape"].write_root_pose_to_sim(root_pose=torch.tensor([0, 0.0, CUBE_CFG.spawn.size[2] / 2.0, 1, 0, 0, 0]))
+        scene["shape"].write_root_pose_to_sim(
+            root_pose=torch.tensor([0, 0.0, CUBE_CFG.spawn.size[2] / 2.0, 1, 0, 0, 0])
+        )
 
         # step sim once to compute friction forces
         _perform_sim_step(sim, scene, sim_dt)
@@ -443,14 +445,16 @@ def test_friction_reporting(setup_simulation, grav_dir):
         friction_force = scene["contact_sensor"]._data.friction_forces_w[0, 0, :]
         friction_magnitude = friction_force.norm().item()
 
-        assert friction_magnitude > 1e-6, "Friction forces should be non-zero"
+        assert friction_magnitude > 1e-2, "Friction forces should be non-zero"
 
         grav = torch.tensor(grav_dir, device=device)
         norm_friction = friction_force / friction_force.norm()
         norm_gravity = grav / grav.norm()
         dot = torch.dot(norm_friction.squeeze(), norm_gravity)
 
-        assert torch.isclose(torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-2), "Friction force should be roughly opposite gravity direction"
+        assert torch.isclose(
+            torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-2
+        ), "Friction force should be roughly opposite gravity direction"
 
 
 """

From 3d5099cbc5e0790663f7e5126bc7b98111d0b17f Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 16:14:54 -0400
Subject: [PATCH 13/33] tuned forces in test

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 361ad943239..68b4637de9e 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -395,7 +395,8 @@ def test_sensor_print(setup_simulation):
         print(scene.sensors["contact_sensor"])
 
 
-@pytest.mark.parametrize("grav_dir", [(-10.0, 0.0, -1.0), (0.0, -10.0, -1.0)])
+# minor gravity force in -z to ensure object stays on ground plane
+@pytest.mark.parametrize("grav_dir", [(-10.0, 0.0, -.1), (0.0, -10.0, -0.1)])
 @pytest.mark.isaacsim_ci
 def test_friction_reporting(setup_simulation, grav_dir):
     """
@@ -453,7 +454,7 @@ def test_friction_reporting(setup_simulation, grav_dir):
         dot = torch.dot(norm_friction.squeeze(), norm_gravity)
 
         assert torch.isclose(
-            torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-2
+            torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4
         ), "Friction force should be roughly opposite gravity direction"
 
 

From 91509ca6ed21c2c0fe68ac5f258ae2989615fe32 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Thu, 25 Sep 2025 16:19:05 -0400
Subject: [PATCH 14/33] adds back friction tracking to check sensor script

---
 source/isaaclab/test/sensors/check_contact_sensor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/isaaclab/test/sensors/check_contact_sensor.py b/source/isaaclab/test/sensors/check_contact_sensor.py
index 32c628d7024..431ab2f47f6 100644
--- a/source/isaaclab/test/sensors/check_contact_sensor.py
+++ b/source/isaaclab/test/sensors/check_contact_sensor.py
@@ -106,7 +106,7 @@ def main():
         prim_path="/World/envs/env_.*/Robot/.*_FOOT",
         track_air_time=True,
         track_contact_points=True,
-        # track_friction_forces=True,
+        track_friction_forces=True,
         debug_vis=False,  # not args_cli.headless,
         filter_prim_paths_expr=["/World/defaultGroundPlane/GroundPlane/CollisionPlane"],
     )

From 23b00ce6eb1288dbdb1efeb333d9ef1ff732b1df Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Fri, 26 Sep 2025 12:56:46 -0400
Subject: [PATCH 15/33] docstring / typing

---
 .../sensors/contact_sensor/contact_sensor.py  | 41 ++++++++++++-------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 7da37c192a2..2179b6edf83 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -394,7 +394,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 dt=self._sim_physics_dt
             )
             self._data.friction_forces_w[env_ids] = self._unpack_contact_data(
-                friction_forces, buffer_count, buffer_start_indices, avg=False
+                friction_forces, buffer_count, buffer_start_indices, avg=False, default=0.0
             )[env_ids]
 
         # obtain the air time
@@ -427,24 +427,35 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 is_contact, self._data.current_contact_time[env_ids] + elapsed_time.unsqueeze(-1), 0.0
             )
 
-    def _unpack_contact_data(self, contact_data, buffer_count, buffer_start_indices, avg=True):
-        # unpack the contact points: see RigidContactView.get_contact_data() documentation for details:
-        # https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
-        # buffer_count: (N_envs * N_bodies, N_filters), contact_points: (N_envs * N_bodies, 3)
+    def _unpack_contact_data(self, contact_data: torch.Tensor, buffer_count: torch.Tensor, buffer_start_indices: torch.Tensor, avg: bool = True, default: float = float("nan")) -> torch.Tensor:
         """
-        Vectorizes the following nested loop:
-        for i in range(self._num_bodies * self._num_envs):
-            for j in range(self.contact_physx_view.filter_count):
-                start_index_ij = buffer_start_indices[i, j]
-                count_ij = buffer_count[i, j]
-                self._contact_position_aggregate_buffer[i, j, :] = torch.mean(
-                    contact_points[start_index_ij : (start_index_ij + count_ij), :], dim=0
-                )
+        Unpacks and aggregates contact data for each (env, body, filter) group.
+
+        This function vectorizes the following nested loop:
+            for i in range(self._num_bodies * self._num_envs):
+                for j in range(self.contact_physx_view.filter_count):
+                    start_index_ij = buffer_start_indices[i, j]
+                    count_ij = buffer_count[i, j]
+                    self._contact_position_aggregate_buffer[i, j, :] = torch.mean(
+                        contact_data[start_index_ij : (start_index_ij + count_ij), :], dim=0
+                    )
+
+        For more details, see the RigidContactView.get_contact_data() documentation:
+        https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
+
+        Args:
+            contact_data (torch.Tensor): Flat tensor of contact data, shape (N_envs * N_bodies, 3).
+            buffer_count (torch.Tensor): Number of contact points per (env, body, filter), shape (N_envs * N_bodies, N_filters).
+            buffer_start_indices (torch.Tensor): Start indices for each (env, body, filter), shape (N_envs * N_bodies, N_filters).
+            avg (bool, optional): If True, average the contact data for each group; if False, sum the data. Defaults to True.
+
+        Returns:
+            torch.Tensor: Aggregated contact data, shape (N_envs, N_bodies, N_filters, 3).
         """
         counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
         n_rows, total = counts.numel(), int(counts.sum())
         # default to NaN rows
-        agg = torch.full((n_rows, 3), float("nan"), device=self._device, dtype=contact_data.dtype)
+        agg = torch.full((n_rows, 3), default, device=self._device, dtype=contact_data.dtype)
         if total > 0:
             row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)
             total = row_ids.numel()
@@ -456,7 +467,7 @@ def _unpack_contact_data(self, contact_data, buffer_count, buffer_start_indices,
             pts = contact_data.index_select(0, flat_idx)
             agg = agg.zero_().index_add_(0, row_ids, pts)
             agg = agg / counts.unsqueeze(-1) if avg else agg
-            agg[counts == 0] = float("nan")
+            agg[counts == 0] = default
 
         return agg.view(self._num_envs * self.num_bodies, -1, 3).view(
             self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3

From 428272cc5093adc7443343eda41699f9cf13c073 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Fri, 26 Sep 2025 12:57:07 -0400
Subject: [PATCH 16/33] formatting

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py    | 9 ++++++++-
 source/isaaclab/test/sensors/test_contact_sensor.py      | 2 +-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 2179b6edf83..7d73ec024bb 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -427,7 +427,14 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 is_contact, self._data.current_contact_time[env_ids] + elapsed_time.unsqueeze(-1), 0.0
             )
 
-    def _unpack_contact_data(self, contact_data: torch.Tensor, buffer_count: torch.Tensor, buffer_start_indices: torch.Tensor, avg: bool = True, default: float = float("nan")) -> torch.Tensor:
+    def _unpack_contact_data(
+        self,
+        contact_data: torch.Tensor,
+        buffer_count: torch.Tensor,
+        buffer_start_indices: torch.Tensor,
+        avg: bool = True,
+        default: float = float("nan"),
+    ) -> torch.Tensor:
         """
         Unpacks and aggregates contact data for each (env, body, filter) group.
 
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 68b4637de9e..13c424eb018 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -396,7 +396,7 @@ def test_sensor_print(setup_simulation):
 
 
 # minor gravity force in -z to ensure object stays on ground plane
-@pytest.mark.parametrize("grav_dir", [(-10.0, 0.0, -.1), (0.0, -10.0, -0.1)])
+@pytest.mark.parametrize("grav_dir", [(-10.0, 0.0, -0.1), (0.0, -10.0, -0.1)])
 @pytest.mark.isaacsim_ci
 def test_friction_reporting(setup_simulation, grav_dir):
     """

From 646bdcb8ff36123b578b1cd9493aa99675d2bc77 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Fri, 26 Sep 2025 16:07:23 -0400
Subject: [PATCH 17/33] test comparing elements of physx friction data with
 reported sensor friction data

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 13c424eb018..65d3be0f7c5 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -443,15 +443,16 @@ def test_friction_reporting(setup_simulation, grav_dir):
         # step sim once to compute friction forces
         _perform_sim_step(sim, scene, sim_dt)
 
-        friction_force = scene["contact_sensor"]._data.friction_forces_w[0, 0, :]
-        friction_magnitude = friction_force.norm().item()
+        # check that forces are being reported match expected friction forces
+        expected_friction, _, _, _ = scene["contact_sensor"].contact_physx_view.get_friction_data(dt=sim_dt)
+        reported_friction = scene["contact_sensor"].data.friction_forces_w[0, 0, :]
 
-        assert friction_magnitude > 1e-2, "Friction forces should be non-zero"
+        assert torch.allclose(expected_friction.sum(dim=0), reported_friction[0], atol=1e-4)
 
         grav = torch.tensor(grav_dir, device=device)
-        norm_friction = friction_force / friction_force.norm()
+        norm_reported_friction = reported_friction / reported_friction.norm()
         norm_gravity = grav / grav.norm()
-        dot = torch.dot(norm_friction.squeeze(), norm_gravity)
+        dot = torch.dot(norm_reported_friction[0], norm_gravity)
 
         assert torch.isclose(
             torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4

From 058c6dc2f958b42a2d9a1f184d807d998dfdfa67 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Fri, 26 Sep 2025 16:16:56 -0400
Subject: [PATCH 18/33] tighter threshold for comparison

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 65d3be0f7c5..4ff22ff986f 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -447,7 +447,7 @@ def test_friction_reporting(setup_simulation, grav_dir):
         expected_friction, _, _, _ = scene["contact_sensor"].contact_physx_view.get_friction_data(dt=sim_dt)
         reported_friction = scene["contact_sensor"].data.friction_forces_w[0, 0, :]
 
-        assert torch.allclose(expected_friction.sum(dim=0), reported_friction[0], atol=1e-4)
+        assert torch.allclose(expected_friction.sum(dim=0), reported_friction[0], atol=1e-6)
 
         grav = torch.tensor(grav_dir, device=device)
         norm_reported_friction = reported_friction / reported_friction.norm()

From 817ed3f959acbb9ed80dff9ab1267426b27b0a66 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:16:44 -0400
Subject: [PATCH 19/33] resetting to zeros

---
 .../isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py  | 2 +-
 source/isaaclab/test/sensors/test_contact_sensor.py             | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 7d73ec024bb..e0688d3f013 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -164,7 +164,7 @@ def reset(self, env_ids: Sequence[int] | None = None):
             self._data.contact_pos_w[env_ids, :] = torch.nan
         # reset friction forces
         if self.cfg.track_friction_forces:
-            self._data.friction_forces_w[env_ids, :] = torch.nan
+            self._data.friction_forces_w[env_ids, :] = torch.zeros
 
     def find_bodies(self, name_keys: str | Sequence[str], preserve_order: bool = False) -> tuple[list[int], list[str]]:
         """Find bodies in the articulation based on the name keys.
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 4ff22ff986f..80ea8260244 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -640,7 +640,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
     # compare friction forces
     if mode == ContactTestMode.IN_CONTACT:
-        assert not torch.any(torch.isnan(sensor._data.friction_forces_w)).item()
+        assert torch.all(torch.is_nonzero(sensor._data.friction_forces_w)).item()
         friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(
             dt=sensor._sim_physics_dt
         )

From a20d58c90513e93d0a0cd2921e8f078ccc2e9659 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:17:51 -0400
Subject: [PATCH 20/33] tests pass

---
 .../isaaclab/sensors/contact_sensor/contact_sensor.py         | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index e0688d3f013..c768c335193 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -164,7 +164,7 @@ def reset(self, env_ids: Sequence[int] | None = None):
             self._data.contact_pos_w[env_ids, :] = torch.nan
         # reset friction forces
         if self.cfg.track_friction_forces:
-            self._data.friction_forces_w[env_ids, :] = torch.zeros
+            self._data.friction_forces_w[env_ids, :] = 0.0
 
     def find_bodies(self, name_keys: str | Sequence[str], preserve_order: bool = False) -> tuple[list[int], list[str]]:
         """Find bodies in the articulation based on the name keys.
@@ -322,7 +322,7 @@ def _initialize_impl(self):
         if self.cfg.track_friction_forces:
             self._data.friction_forces_w = torch.full(
                 (self._num_envs, self._num_bodies, self.contact_physx_view.filter_count, 3),
-                torch.nan,
+                0.0,
                 device=self._device,
             )
         # -- air/contact time between contacts

From d81d3986b07eacdd11502c44f22404a898ac5388 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:40:19 -0400
Subject: [PATCH 21/33] add param to docstring

---
 .../isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py   | 1 +
 1 file changed, 1 insertion(+)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index c768c335193..a85ab4a7a62 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -455,6 +455,7 @@ def _unpack_contact_data(
             buffer_count (torch.Tensor): Number of contact points per (env, body, filter), shape (N_envs * N_bodies, N_filters).
             buffer_start_indices (torch.Tensor): Start indices for each (env, body, filter), shape (N_envs * N_bodies, N_filters).
             avg (bool, optional): If True, average the contact data for each group; if False, sum the data. Defaults to True.
+            default (float, optional): Default value to use for groups with zero contacts. Defaults to NaN.
 
         Returns:
             torch.Tensor: Aggregated contact data, shape (N_envs, N_bodies, N_filters, 3).

From 51c4f6346c10c973b600242b1551a6f3d3a6f5a7 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:40:48 -0400
Subject: [PATCH 22/33] comment formatting

---
 .../sensors/contact_sensor/contact_sensor.py      | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index a85ab4a7a62..2cd16d274af 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -439,13 +439,14 @@ def _unpack_contact_data(
         Unpacks and aggregates contact data for each (env, body, filter) group.
 
         This function vectorizes the following nested loop:
-            for i in range(self._num_bodies * self._num_envs):
-                for j in range(self.contact_physx_view.filter_count):
-                    start_index_ij = buffer_start_indices[i, j]
-                    count_ij = buffer_count[i, j]
-                    self._contact_position_aggregate_buffer[i, j, :] = torch.mean(
-                        contact_data[start_index_ij : (start_index_ij + count_ij), :], dim=0
-                    )
+
+        for i in range(self._num_bodies * self._num_envs):
+            for j in range(self.contact_physx_view.filter_count):
+                start_index_ij = buffer_start_indices[i, j]
+                count_ij = buffer_count[i, j]
+                self._contact_position_aggregate_buffer[i, j, :] = torch.mean(
+                    contact_data[start_index_ij : (start_index_ij + count_ij), :], dim=0
+                )
 
         For more details, see the RigidContactView.get_contact_data() documentation:
         https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces

From 6c0441e10eae0fde7d452f8c88fe2a02f3111750 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:46:45 -0400
Subject: [PATCH 23/33] setting gravity in sim cfg

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 80ea8260244..c7ca64a1832 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -27,7 +27,7 @@
 from isaaclab.assets import RigidObject, RigidObjectCfg
 from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
 from isaaclab.sensors import ContactSensor, ContactSensorCfg
-from isaaclab.sim import SimulationContext, build_simulation_context
+from isaaclab.sim import SimulationContext, SimulationCfg, build_simulation_context
 from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg
 from isaaclab.utils import configclass
 
@@ -408,7 +408,8 @@ def test_friction_reporting(setup_simulation, grav_dir):
     sim_dt, _, _, _, carb_settings_iface = setup_simulation
     carb_settings_iface.set_bool("/physics/disableContactProcessing", True)
     device = "cuda:0"
-    with build_simulation_context(device=device, dt=sim_dt, add_lighting=False) as sim:
+    sim_cfg = SimulationCfg(dt=sim_dt, device=device, gravity=grav_dir)
+    with build_simulation_context(sim_cfg=sim_cfg, add_lighting=False) as sim:
         sim._app_control_on_stop_handle = None
 
         scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
@@ -430,9 +431,6 @@ def test_friction_reporting(setup_simulation, grav_dir):
 
         scene = InteractiveScene(scene_cfg)
 
-        # set custom gravity
-        UsdPhysics.Scene.Get(scene.stage, "/physicsScene").CreateGravityDirectionAttr().Set(Gf.Vec3f(*grav_dir))
-
         sim.reset()
 
         scene["contact_sensor"].reset()

From 53aed8a2f9e474df6359643228b6cb21d2de5509 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 10:48:35 -0400
Subject: [PATCH 24/33] remove unused imports

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index c7ca64a1832..30201e1d363 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -21,7 +21,6 @@
 import carb
 import pytest
 from flaky import flaky
-from pxr import Gf, UsdPhysics
 
 import isaaclab.sim as sim_utils
 from isaaclab.assets import RigidObject, RigidObjectCfg

From 1fbdb77941c08208ad3c36504de89e72eec2a36a Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 29 Sep 2025 14:35:50 -0400
Subject: [PATCH 25/33] formatter

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 30201e1d363..61e05a39d8e 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -26,7 +26,7 @@
 from isaaclab.assets import RigidObject, RigidObjectCfg
 from isaaclab.scene import InteractiveScene, InteractiveSceneCfg
 from isaaclab.sensors import ContactSensor, ContactSensorCfg
-from isaaclab.sim import SimulationContext, SimulationCfg, build_simulation_context
+from isaaclab.sim import SimulationCfg, SimulationContext, build_simulation_context
 from isaaclab.terrains import HfRandomUniformTerrainCfg, TerrainGeneratorCfg, TerrainImporterCfg
 from isaaclab.utils import configclass
 

From 536b4a5a6dc4e7d9b26863326c8b83a2d548b565 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 20 Oct 2025 13:59:13 -0400
Subject: [PATCH 26/33] updated tests

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 61e05a39d8e..d4afc905432 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -637,7 +637,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
     assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
     # compare friction forces
     if mode == ContactTestMode.IN_CONTACT:
-        assert torch.all(torch.is_nonzero(sensor._data.friction_forces_w)).item()
+        assert torch.any(torch.abs(sensor._data.friction_forces_w) > 1e-5).item()
         friction_forces, _, buffer_count, buffer_start_indices = sensor.contact_physx_view.get_friction_data(
             dt=sensor._sim_physics_dt
         )
@@ -649,7 +649,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
                 assert torch.allclose(force, sensor._data.friction_forces_w[i, j, :], atol=1e-5)
 
     elif mode == ContactTestMode.NON_CONTACT:
-        assert torch.all(torch.isnan(sensor._data.friction_forces_w)).item()
+        assert torch.all(sensor._data.friction_forces_w == 0.0).item()
 
 
 def _test_contact_position(shape: RigidObject, sensor: ContactSensor, mode: ContactTestMode) -> None:

From 033760685b79618c55f715400389e050541d4753 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 20 Oct 2025 16:20:26 -0400
Subject: [PATCH 27/33] removed unhelpful comment

---
 .../isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py   | 1 -
 1 file changed, 1 deletion(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 2cd16d274af..d4128c0e3da 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -463,7 +463,6 @@ def _unpack_contact_data(
         """
         counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
         n_rows, total = counts.numel(), int(counts.sum())
-        # default to NaN rows
         agg = torch.full((n_rows, 3), default, device=self._device, dtype=contact_data.dtype)
         if total > 0:
             row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)

From 9972b9b7735642f5f0c94978a5e0106a47b066c9 Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 22 Oct 2025 11:26:08 -0400
Subject: [PATCH 28/33] addressing pr comments

---
 source/isaaclab/docs/CHANGELOG.rst            |  2 ++
 .../sensors/contact_sensor/contact_sensor.py  | 26 +++++++++----------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/source/isaaclab/docs/CHANGELOG.rst b/source/isaaclab/docs/CHANGELOG.rst
index e625b2470af..ceee33374b5 100644
--- a/source/isaaclab/docs/CHANGELOG.rst
+++ b/source/isaaclab/docs/CHANGELOG.rst
@@ -6,9 +6,11 @@ Changelog
 
 Added
 ^^^^^
+
 * Added :attr:`~isaaclab.sensors.contact_sensor.ContactSensorCfg.track_friction_forces` to toggle tracking of friction forces between sensor bodies and filtered bodies.
 * Added :attr:`~isaaclab.sensors.contact_sensor.ContactSensorData.friction_forces_w` data field for tracking friction forces.
 
+
 0.47.1 (2025-10-17)
 ~~~~~~~~~~~~~~~~~~~
 
diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index d4128c0e3da..5c84c36492d 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -384,7 +384,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             _, buffer_contact_points, _, _, buffer_count, buffer_start_indices = (
                 self.contact_physx_view.get_contact_data(dt=self._sim_physics_dt)
             )
-            self._data.contact_pos_w[env_ids] = self._unpack_contact_data(
+            self._data.contact_pos_w[env_ids] = self._unpack_contact_buffer_data(
                 buffer_contact_points, buffer_count, buffer_start_indices
             )[env_ids]
 
@@ -393,7 +393,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
             friction_forces, _, buffer_count, buffer_start_indices = self.contact_physx_view.get_friction_data(
                 dt=self._sim_physics_dt
             )
-            self._data.friction_forces_w[env_ids] = self._unpack_contact_data(
+            self._data.friction_forces_w[env_ids] = self._unpack_contact_buffer_data(
                 friction_forces, buffer_count, buffer_start_indices, avg=False, default=0.0
             )[env_ids]
 
@@ -427,7 +427,7 @@ def _update_buffers_impl(self, env_ids: Sequence[int]):
                 is_contact, self._data.current_contact_time[env_ids] + elapsed_time.unsqueeze(-1), 0.0
             )
 
-    def _unpack_contact_data(
+    def _unpack_contact_buffer_data(
         self,
         contact_data: torch.Tensor,
         buffer_count: torch.Tensor,
@@ -448,33 +448,31 @@ def _unpack_contact_data(
                     contact_data[start_index_ij : (start_index_ij + count_ij), :], dim=0
                 )
 
-        For more details, see the RigidContactView.get_contact_data() documentation:
-        https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_net_contact_forces
+        For more details, see the `RigidContactView.get_contact_data() documentation <https://docs.omniverse.nvidia.com/kit/docs/omni_physics/107.3/extensions/runtime/source/omni.physics.tensors/docs/api/python.html#omni.physics.tensors.impl.api.RigidContactView.get_contact_data>`_.
 
         Args:
-            contact_data (torch.Tensor): Flat tensor of contact data, shape (N_envs * N_bodies, 3).
-            buffer_count (torch.Tensor): Number of contact points per (env, body, filter), shape (N_envs * N_bodies, N_filters).
-            buffer_start_indices (torch.Tensor): Start indices for each (env, body, filter), shape (N_envs * N_bodies, N_filters).
-            avg (bool, optional): If True, average the contact data for each group; if False, sum the data. Defaults to True.
-            default (float, optional): Default value to use for groups with zero contacts. Defaults to NaN.
+            contact_data: Flat tensor of contact data, shape (N_envs * N_bodies, 3).
+            buffer_count: Number of contact points per (env, body, filter), shape (N_envs * N_bodies, N_filters).
+            buffer_start_indices: Start indices for each (env, body, filter), shape (N_envs * N_bodies, N_filters).
+            avg: If True, average the contact data for each group; if False, sum the data. Defaults to True.
+            default: Default value to use for groups with zero contacts. Defaults to NaN.
 
         Returns:
-            torch.Tensor: Aggregated contact data, shape (N_envs, N_bodies, N_filters, 3).
+            Aggregated contact data, shape (N_envs, N_bodies, N_filters, 3).
         """
         counts, starts = buffer_count.view(-1), buffer_start_indices.view(-1)
         n_rows, total = counts.numel(), int(counts.sum())
         agg = torch.full((n_rows, 3), default, device=self._device, dtype=contact_data.dtype)
         if total > 0:
             row_ids = torch.repeat_interleave(torch.arange(n_rows, device=self._device), counts)
-            total = row_ids.numel()
 
             block_starts = counts.cumsum(0) - counts
-            deltas = torch.arange(total, device=counts.device) - block_starts.repeat_interleave(counts)
+            deltas = torch.arange(row_ids.numel(), device=counts.device) - block_starts.repeat_interleave(counts)
             flat_idx = starts[row_ids] + deltas
 
             pts = contact_data.index_select(0, flat_idx)
             agg = agg.zero_().index_add_(0, row_ids, pts)
-            agg = agg / counts.unsqueeze(-1) if avg else agg
+            agg = agg / counts.clamp_min(1).unsqueeze(-1) if avg else agg
             agg[counts == 0] = default
 
         return agg.view(self._num_envs * self.num_bodies, -1, 3).view(

From 6e6486e30638e30155988bbaec8cb1e9c1b6d17f Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 22 Oct 2025 13:43:51 -0400
Subject: [PATCH 29/33] using torch.testing / working on test for invalid
 config

---
 .../contact_sensor/contact_sensor_data.py     |  2 +-
 .../test/sensors/test_contact_sensor.py       | 46 +++++++++++++++++--
 2 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
index 8a1c6c2947c..dd5e5aa8431 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
@@ -41,7 +41,7 @@ class ContactSensorData:
     """
 
     friction_forces_w: torch.Tensor | None = None
-    """Average of the friction forces between sensor body and filter prim in world frame.
+    """Sum of the friction forces between sensor body and filter prim in world frame.
 
     Shape is (N, B, M, 3), where N is the number of sensors, B is number of bodies in each sensor
     and M is the number of filtered bodies.
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index d4afc905432..74ee1fc0cc4 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -444,16 +444,54 @@ def test_friction_reporting(setup_simulation, grav_dir):
         expected_friction, _, _, _ = scene["contact_sensor"].contact_physx_view.get_friction_data(dt=sim_dt)
         reported_friction = scene["contact_sensor"].data.friction_forces_w[0, 0, :]
 
-        assert torch.allclose(expected_friction.sum(dim=0), reported_friction[0], atol=1e-6)
+        torch.testing.assert_close(expected_friction.sum(dim=0), reported_friction[0], atol=1e-6)
 
+        # check that friction force direction opposes gravity direction
         grav = torch.tensor(grav_dir, device=device)
         norm_reported_friction = reported_friction / reported_friction.norm()
         norm_gravity = grav / grav.norm()
         dot = torch.dot(norm_reported_friction[0], norm_gravity)
 
-        assert torch.isclose(
-            torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4
-        ), "Friction force should be roughly opposite gravity direction"
+        torch.testing.assert_close(torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4)
+
+
+@pytest.mark.isaacsim_ci
+def test_invalid_config(setup_simulation):
+    sim_dt, _, _, _, carb_settings_iface = setup_simulation
+    carb_settings_iface.set_bool("/physics/disableContactProcessing", True)
+    device = "cuda:0"
+    sim_cfg = SimulationCfg(dt=sim_dt, device=device)
+    with build_simulation_context(sim_cfg=sim_cfg, add_lighting=False) as sim:
+        sim._app_control_on_stop_handle = None
+
+        scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
+        scene_cfg.terrain = FLAT_TERRAIN_CFG
+        scene_cfg.shape = CUBE_CFG
+
+        # filter_prim_paths_expr = [scene_cfg.terrain.prim_path + "/terrain/GroundPlane/CollisionPlane"]
+
+        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,
+            track_friction_forces=True,
+            filter_prim_paths_expr=[],
+        )
+
+        scene = InteractiveScene(scene_cfg)
+
+        sim.reset()
+
+        scene["contact_sensor"].reset()
+        scene["shape"].write_root_pose_to_sim(
+            root_pose=torch.tensor([0, 0.0, CUBE_CFG.spawn.size[2] / 2.0, 1, 0, 0, 0])
+        )
+
+        # step sim once to compute friction forces
+        _perform_sim_step(sim, scene, sim_dt)
 
 
 """

From 551a24509bc43e8932e1593aa341e7ae0a01beca Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 22 Oct 2025 14:03:47 -0400
Subject: [PATCH 30/33] config tests

---
 .../sensors/contact_sensor/contact_sensor.py  | 15 ++++++
 .../test/sensors/test_contact_sensor.py       | 51 +++++++++++++++----
 2 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
index 5c84c36492d..676d6272ff2 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor.py
@@ -311,6 +311,21 @@ def _initialize_impl(self):
         if self.cfg.track_pose:
             self._data.pos_w = torch.zeros(self._num_envs, self._num_bodies, 3, device=self._device)
             self._data.quat_w = torch.zeros(self._num_envs, self._num_bodies, 4, device=self._device)
+
+        # check if filter paths are valid
+        if self.cfg.track_contact_points or self.cfg.track_friction_forces:
+            if len(self.cfg.filter_prim_paths_expr) == 0:
+                raise ValueError(
+                    "The 'filter_prim_paths_expr' is empty. Please specify a valid filter pattern to track"
+                    f" {'contact points' if self.cfg.track_contact_points else 'friction forces'}."
+                )
+            if self.cfg.max_contact_data_count_per_prim < 1:
+                raise ValueError(
+                    f"The 'max_contact_data_count_per_prim' is {self.cfg.max_contact_data_count_per_prim}. "
+                    "Please set it to a value greater than 0 to track"
+                    f" {'contact points' if self.cfg.track_contact_points else 'friction forces'}."
+                )
+
         # -- position of contact points
         if self.cfg.track_contact_points:
             self._data.contact_pos_w = torch.full(
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index 74ee1fc0cc4..f8b9fc374ac 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -456,7 +456,7 @@ def test_friction_reporting(setup_simulation, grav_dir):
 
 
 @pytest.mark.isaacsim_ci
-def test_invalid_config(setup_simulation):
+def test_invalid_prim_paths_config(setup_simulation):
     sim_dt, _, _, _, carb_settings_iface = setup_simulation
     carb_settings_iface.set_bool("/physics/disableContactProcessing", True)
     device = "cuda:0"
@@ -468,8 +468,6 @@ def test_invalid_config(setup_simulation):
         scene_cfg.terrain = FLAT_TERRAIN_CFG
         scene_cfg.shape = CUBE_CFG
 
-        # filter_prim_paths_expr = [scene_cfg.terrain.prim_path + "/terrain/GroundPlane/CollisionPlane"]
-
         scene_cfg.contact_sensor = ContactSensorCfg(
             prim_path=scene_cfg.shape.prim_path,
             track_pose=True,
@@ -481,17 +479,50 @@ def test_invalid_config(setup_simulation):
             filter_prim_paths_expr=[],
         )
 
-        scene = InteractiveScene(scene_cfg)
+        try:
+            _ = InteractiveScene(scene_cfg)
 
-        sim.reset()
+            sim.reset()
 
-        scene["contact_sensor"].reset()
-        scene["shape"].write_root_pose_to_sim(
-            root_pose=torch.tensor([0, 0.0, CUBE_CFG.spawn.size[2] / 2.0, 1, 0, 0, 0])
+            assert False, "Expected ValueError due to invalid contact sensor configuration."
+        except ValueError:
+            pass
+
+
+@pytest.mark.isaacsim_ci
+def test_invalid_max_contact_points_config(setup_simulation):
+    sim_dt, _, _, _, carb_settings_iface = setup_simulation
+    carb_settings_iface.set_bool("/physics/disableContactProcessing", True)
+    device = "cuda:0"
+    sim_cfg = SimulationCfg(dt=sim_dt, device=device)
+    with build_simulation_context(sim_cfg=sim_cfg, add_lighting=False) as sim:
+        sim._app_control_on_stop_handle = None
+
+        scene_cfg = ContactSensorSceneCfg(num_envs=1, env_spacing=1.0, lazy_sensor_update=False)
+        scene_cfg.terrain = FLAT_TERRAIN_CFG
+        scene_cfg.shape = CUBE_CFG
+        filter_prim_paths_expr = [scene_cfg.terrain.prim_path + "/terrain/GroundPlane/CollisionPlane"]
+
+        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,
+            track_friction_forces=True,
+            filter_prim_paths_expr=filter_prim_paths_expr,
+            max_contact_data_count_per_prim=0,
         )
 
-        # step sim once to compute friction forces
-        _perform_sim_step(sim, scene, sim_dt)
+        try:
+            _ = InteractiveScene(scene_cfg)
+
+            sim.reset()
+
+            assert False, "Expected ValueError due to invalid contact sensor configuration."
+        except ValueError:
+            pass
 
 
 """

From 1ed5152cac70b53e7dbe10a58c7d250f5c48584d Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 22 Oct 2025 14:07:08 -0400
Subject: [PATCH 31/33] atol/rtol

---
 source/isaaclab/test/sensors/test_contact_sensor.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index f8b9fc374ac..c8c61d770c0 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -444,7 +444,7 @@ def test_friction_reporting(setup_simulation, grav_dir):
         expected_friction, _, _, _ = scene["contact_sensor"].contact_physx_view.get_friction_data(dt=sim_dt)
         reported_friction = scene["contact_sensor"].data.friction_forces_w[0, 0, :]
 
-        torch.testing.assert_close(expected_friction.sum(dim=0), reported_friction[0], atol=1e-6)
+        torch.testing.assert_close(expected_friction.sum(dim=0), reported_friction[0], atol=1e-6, rtol=1e-5)
 
         # check that friction force direction opposes gravity direction
         grav = torch.tensor(grav_dir, device=device)
@@ -452,7 +452,7 @@ def test_friction_reporting(setup_simulation, grav_dir):
         norm_gravity = grav / grav.norm()
         dot = torch.dot(norm_reported_friction[0], norm_gravity)
 
-        torch.testing.assert_close(torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4)
+        torch.testing.assert_close(torch.abs(dot), torch.tensor(1.0, device=device), atol=1e-4, rtol=1e-3)
 
 
 @pytest.mark.isaacsim_ci

From a4b0c83789c932f32114668d9012e71a999ba70a Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Wed, 22 Oct 2025 14:11:28 -0400
Subject: [PATCH 32/33] updated docstring

---
 .../sensors/contact_sensor/contact_sensor_data.py  | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
index dd5e5aa8431..c2b6f814bdd 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
@@ -35,9 +35,10 @@ class ContactSensorData:
     Note:
 
         * If the :attr:`ContactSensorCfg.track_contact_points` is False, then this quantity is None.
-        * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty, then this quantity is an empty tensor.
-        * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1, then this quantity
-          will not be calculated.
+        * If the :attr:`ContactSensorCfg.track_contact_points` is True, a ValueError will be raised if:
+            * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
+            * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
+            will not be calculated.
     """
 
     friction_forces_w: torch.Tensor | None = None
@@ -51,9 +52,10 @@ class ContactSensorData:
     Note:
 
         * If the :attr:`ContactSensorCfg.track_friction_forces` is False, then this quantity is None.
-        * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty, then this quantity is an empty tensor.
-        * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1, then this quantity
-          will not be calculated.
+        * If the :attr:`ContactSensorCfg.track_friction_forces` is True, a ValueError will be raised if:
+            * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
+            * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
+            will not be calculated.
     """
 
     quat_w: torch.Tensor | None = None

From 47b9ce38443a8652d8fd0736ca3deda6acb5ac2d Mon Sep 17 00:00:00 2001
From: Greg Attra <gattra@rai-inst.com>
Date: Mon, 27 Oct 2025 13:20:12 -0400
Subject: [PATCH 33/33] formatting

---
 .../sensors/contact_sensor/contact_sensor_data.py    | 12 ++++++------
 source/isaaclab/test/sensors/test_contact_sensor.py  |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
index c2b6f814bdd..529e286269b 100644
--- a/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
+++ b/source/isaaclab/isaaclab/sensors/contact_sensor/contact_sensor_data.py
@@ -36,9 +36,9 @@ class ContactSensorData:
 
         * If the :attr:`ContactSensorCfg.track_contact_points` is False, then this quantity is None.
         * If the :attr:`ContactSensorCfg.track_contact_points` is True, a ValueError will be raised if:
-            * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
-            * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
-            will not be calculated.
+        * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
+        * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
+        will not be calculated.
     """
 
     friction_forces_w: torch.Tensor | None = None
@@ -53,9 +53,9 @@ class ContactSensorData:
 
         * If the :attr:`ContactSensorCfg.track_friction_forces` is False, then this quantity is None.
         * If the :attr:`ContactSensorCfg.track_friction_forces` is True, a ValueError will be raised if:
-            * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
-            * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
-            will not be calculated.
+        * If the :attr:`ContactSensorCfg.filter_prim_paths_expr` is empty.
+        * If the :attr:`ContactSensorCfg.max_contact_data_per_prim` is not specified or less than 1.
+        will not be calculated.
     """
 
     quat_w: torch.Tensor | None = None
diff --git a/source/isaaclab/test/sensors/test_contact_sensor.py b/source/isaaclab/test/sensors/test_contact_sensor.py
index c8c61d770c0..2876063e6fb 100644
--- a/source/isaaclab/test/sensors/test_contact_sensor.py
+++ b/source/isaaclab/test/sensors/test_contact_sensor.py
@@ -703,7 +703,7 @@ def _test_friction_forces(shape: RigidObject, sensor: ContactSensor, mode: Conta
 
     # check shape of the contact_pos_w tensor
     num_bodies = sensor.num_bodies
-    assert sensor._data.friction_forces_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
+    assert sensor._data.friction_forces_w.shape == (sensor.num_instances // num_bodies, num_bodies, 1, 3)
     # compare friction forces
     if mode == ContactTestMode.IN_CONTACT:
         assert torch.any(torch.abs(sensor._data.friction_forces_w) > 1e-5).item()
@@ -735,7 +735,7 @@ def _test_contact_position(shape: RigidObject, sensor: ContactSensor, mode: Cont
 
     # check shape of the contact_pos_w tensor
     num_bodies = sensor.num_bodies
-    assert sensor._data.contact_pos_w.shape == (sensor.num_instances / num_bodies, num_bodies, 1, 3)
+    assert sensor._data.contact_pos_w.shape == (sensor.num_instances // num_bodies, num_bodies, 1, 3)
     # check contact positions
     if mode == ContactTestMode.IN_CONTACT:
         contact_position = sensor._data.pos_w + torch.tensor(