Adds CoM randomization term to manager-based events (#1714)

# Description

Introduced CoM randomization in events.py for manager based envs.
Individual range can be selected for individual axis and bodies.

Thanks to #641 and #693  for motivation of the code.  

## Type of change

- New feature (non-breaking change which adds functionality)
- This change requires a documentation update

## Checklist

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

CONTRIBUTORS.md

@@ -51,6 +51,7 @@ Guidelines for modifications:
 * Connor Smith
 * CY (Chien-Ying) Chen
 * David Yang
+* Dhananjay Shendre
 * Dorsa Rohani
 * Felipe Mohr
 * Felix Yu

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

@@ -351,6 +351,49 @@ def randomize_rigid_body_mass(
         asset.root_physx_view.set_inertias(inertias, env_ids)
 
 
+def randomize_rigid_body_com(
+    env: ManagerBasedEnv,
+    env_ids: torch.Tensor | None,
+    com_range: dict[str, tuple[float, float]],
+    asset_cfg: SceneEntityCfg,
+):
+    """Randomize the center of mass (CoM) of rigid bodies by adding a random value sampled from the given ranges.
+
+    .. note::
+        This function uses CPU tensors to assign the CoM. It is recommended to use this function
+        only during the initialization of the environment.
+    """
+    # extract the used quantities (to enable type-hinting)
+    asset: Articulation = env.scene[asset_cfg.name]
+    # resolve environment ids
+    if env_ids is None:
+        env_ids = torch.arange(env.scene.num_envs, device="cpu")
+    else:
+        env_ids = env_ids.cpu()
+
+    # resolve body indices
+    if asset_cfg.body_ids == slice(None):
+        body_ids = torch.arange(asset.num_bodies, dtype=torch.int, device="cpu")
+    else:
+        body_ids = torch.tensor(asset_cfg.body_ids, dtype=torch.int, device="cpu")
+
+    # sample random CoM values
+    range_list = [com_range.get(key, (0.0, 0.0)) for key in ["x", "y", "z"]]
+    ranges = torch.tensor(range_list, device="cpu")
+    rand_samples = math_utils.sample_uniform(
+        ranges[:, 0], ranges[:, 1], (len(env_ids), len(body_ids), 3), device="cpu"
+    ).unsqueeze(1)
+
+    # get the current com of the bodies (num_assets, num_bodies)
+    coms = asset.root_physx_view.get_coms().clone()
+
+    # Randomize the com in range
+    coms[:, body_ids, :3] += rand_samples
+
+    # Set the new coms
+    asset.root_physx_view.set_coms(coms, env_ids)
+
+
 def randomize_rigid_body_collider_offsets(
     env: ManagerBasedEnv,
     env_ids: torch.Tensor | None,

source/isaaclab_tasks/isaaclab_tasks/manager_based/locomotion/velocity/velocity_env_cfg.py

@@ -173,6 +173,15 @@ class EventCfg:
         },
     )
 
+    base_com = EventTerm(
+        func=mdp.randomize_rigid_body_com,
+        mode="startup",
+        params={
+            "asset_cfg": SceneEntityCfg("robot", body_names="base"),
+            "com_range": {"x": (-0.05, 0.05), "y": (-0.05, 0.05), "z": (-0.01, 0.01)},
+        },
+    )
+
     # reset
     base_external_force_torque = EventTerm(
         func=mdp.apply_external_force_torque,