Skips apply_external_force_torque when both ranges are zero

source/isaaclab/changelog.d/fix-zero-wrench-fast-path.rst

@@ -0,0 +1,12 @@
+Fixed
+^^^^^
+
+* Fixed a per-step performance regression in :func:`~isaaclab.envs.mdp.events.apply_external_force_torque`
+  when the event was configured with all-zero ``force_range`` and ``torque_range`` (a common default
+  for tasks that declare the event term but apply no disturbance). The event was unconditionally
+  sampling zero wrenches and routing them through the dual-buffer ``WrenchComposer`` introduced in
+  PR #5265, paying the full per-step compose-and-apply cost in
+  :meth:`~isaaclab.assets.Articulation.write_data_to_sim` for what is semantically a no-op. The
+  function now returns early when both ranges are exactly zero. This restores the H1, G1, and
+  Anymal-C ``Velocity-Rough`` throughput observed prior to PR #5265. Behaviour for non-zero ranges
+  is unchanged.

source/isaaclab/isaaclab/envs/mdp/events.py

@@ -1709,6 +1709,10 @@ def apply_external_force_torque(
     # resolve number of bodies
     num_bodies = len(asset_cfg.body_ids) if isinstance(asset_cfg.body_ids, list) else asset.num_bodies
 
+    # Skip force application if the wrench ranges are zero
+    if force_range[0] == 0.0 and force_range[1] == 0.0 and torque_range[0] == 0.0 and torque_range[1] == 0.0:
+        return
+
     # sample random forces and torques
     size = (len(env_ids), num_bodies, 3)
     forces = math_utils.sample_uniform(*force_range, size, asset.device)