Enable rough terrain for bipeds (H1, Cassie) and Digit on Newton

Restore per-biped overrides dropped by parent PR's consolidation:
- All bipeds (H1, Cassie, G1, Digit): restore
  reset_robot_joints.params["position_range"] = (1.0, 1.0). Bipeds
  have precise init poses that should not be randomly scaled on reset.
- Cassie: add leg armature=0.02 for stability on rough terrain.

Out of scope (pre-existing issues that fail on PhysX too):
- G1: finger joints dilute learning; addressed in follow-up PR.
- Digit: closed-loop kinematics fail in 7 steps on both backends.

Author: hujc7

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/cassie/rough_env_cfg.py

@@ -13,6 +13,7 @@
     LocomotionVelocityRoughEnvCfg,
     RewardsCfg,
 )
+from isaaclab_tasks.utils import preset
 
 ##
 # Pre-defined configs
@@ -60,12 +61,18 @@ def __post_init__(self):
         super().__post_init__()
         # scene
         self.scene.robot = CASSIE_CFG.replace(prim_path="{ENV_REGEX_NS}/Robot")
+        # Cassie Newton-only armature for biped stability on rough terrain; PhysX unchanged
+        self.scene.robot.actuators["legs"].armature = preset(default=0.0, newton=0.02)
+
+
         self.scene.height_scanner.prim_path = "{ENV_REGEX_NS}/Robot/pelvis"
 
         # Cassie uses "pelvis" as base body — disable mass randomization for bipeds
         self.events.add_base_mass = None
         self.events.base_com = None
         self.events.base_external_force_torque.params["asset_cfg"].body_names = ".*pelvis"
+        # Cassie has precise initial pose — don't scale joint defaults randomly on reset
+        self.events.reset_robot_joints.params["position_range"] = (1.0, 1.0)
 
         # actions
         self.actions.joint_pos.scale = 0.5

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/digit/rough_env_cfg.py

@@ -232,6 +232,8 @@ def __post_init__(self):
         self.events.add_base_mass.params["asset_cfg"].body_names = "torso_base"
         self.events.base_external_force_torque.params["asset_cfg"].body_names = "torso_base"
         self.events.base_com.default.params["asset_cfg"].body_names = "torso_base"
+        # Digit has precise initial pose — don't scale joint defaults randomly on reset
+        self.events.reset_robot_joints.params["position_range"] = (1.0, 1.0)
 
         # Override actuator to target only actuated joints. Digit has ball joints (rod constraints)
         # that MuJoCo represents with 4 DoFs instead of 3, inflating joint_pos to 74 columns while

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/g1/rough_env_cfg.py

@@ -119,6 +119,8 @@ def __post_init__(self):
         self.events.add_base_mass = None
         self.events.base_com = None
         self.events.base_external_force_torque.params["asset_cfg"].body_names = "torso_link"
+        # G1 has precise initial pose — don't scale joint defaults randomly on reset
+        self.events.reset_robot_joints.params["position_range"] = (1.0, 1.0)
 
         # Rewards
         self.rewards.lin_vel_z_l2.weight = 0.0

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/config/h1/rough_env_cfg.py

@@ -85,6 +85,8 @@ def __post_init__(self):
 
         # H1 uses "torso_link" as base body — disable mass randomization for bipeds
         self.events.add_base_mass = None
+        # H1 has precise initial pose — don't scale joint defaults randomly on reset
+        self.events.reset_robot_joints.params["position_range"] = (1.0, 1.0)
         self.events.base_com = None
         self.events.base_external_force_torque.params["asset_cfg"].body_names = ".*torso_link"