export usd

docs/source/overview/sim/sim_manager.md

@@ -85,6 +85,44 @@ The manager provides methods to add, retrieve and remove various simulation asse
 
 For more details on simulation assets, please refer to their respective documentation pages.
 
+### USD Import and Export
+
+#### Importing USD Files
+
+EmbodiChain supports importing USD files (`.usd`, `.usda`, `.usdc`) for both rigid objects and articulations. When importing USD files, you can choose whether to use the physical properties defined in the USD file or override them with configuration values:
+
+```python
+# Import rigid object with USD properties
+rigid_cfg = RigidObjectCfg(
+    shape=MeshCfg(fpath=get_data_path("path/to/object.usd")),
+    use_usd_properties=True  # Use properties from USD file
+)
+obj = sim.add_rigid_object(cfg=rigid_cfg)
+
+# Import articulation with USD properties
+robot_cfg = ArticulationCfg(
+    fpath=get_data_path("path/to/robot.usd"),
+    use_usd_properties=True  # Use joint drive properties from USD
+)
+robot = sim.add_articulation(cfg=robot_cfg)
+```
+
+#### Exporting to USD
+
+You can export the current simulation scene to a USD file using the `export_usd()` method:
+
+```python
+# Export the entire scene to USD
+sim.export_usd("my_scene.usda")
+```
+
+This exports all objects, articulations, robots, and their current states to a USD file, which can be:
+- Reimported into EmbodiChain with preserved properties
+- Opened in USD-compatible tools (e.g., USD Viewer, Omniverse)
+- Used as assets for other simulations
+
+See `scripts/tutorials/sim/export_usd.py` for a complete example.
+
 ## Simulation Loop
 
 ### Manual Update mode

embodichain/lab/sim/objects/articulation.py

@@ -629,6 +629,24 @@ def __init__(
             self.default_joint_max_effort = self._data.qf_limits.clone()
             self.default_joint_max_velocity = self._data.qvel_limits.clone()
 
+            # Write the USD properties back to cfg
+            usd_drive_pros = self.cfg.drive_pros
+            usd_drive_pros.stiffness = (
+                self.default_joint_stiffness[0].cpu().numpy().tolist()
+            )
+            usd_drive_pros.damping = (
+                self.default_joint_damping[0].cpu().numpy().tolist()
+            )
+            usd_drive_pros.friction = (
+                self.default_joint_friction[0].cpu().numpy().tolist()
+            )
+            usd_drive_pros.max_effort = (
+                self.default_joint_max_effort[0].cpu().numpy().tolist()
+            )
+            usd_drive_pros.max_velocity = (
+                self.default_joint_max_velocity[0].cpu().numpy().tolist()
+            )
+
         self.pk_chain = None
         if self.cfg.build_pk_chain:
             self.pk_chain = create_pk_chain(

embodichain/lab/sim/objects/rigid_object.py

@@ -216,6 +216,15 @@ def __init__(
             for entity in entities:
                 entity.set_body_scale(*cfg.body_scale)
                 entity.set_physical_attr(cfg.attrs.attr())
+        else:
+            # Read current properties from USD-loaded entities and write back to cfg
+            # Use first entity as reference
+            first_entity: MeshObject = entities[0]
+
+            cfg.body_scale = tuple(first_entity.get_body_scale())
+            cfg.attrs = RigidBodyAttributesCfg().from_dict(
+                first_entity.get_physical_attr().as_dict()
+            )
 
         if device.type == "cuda":
             self._world.update(0.001)
@@ -872,8 +881,7 @@ def reset(self, env_ids: Sequence[int] | None = None) -> None:
         local_env_ids = self._all_indices if env_ids is None else env_ids
         num_instances = len(local_env_ids)
 
-        if not self.cfg.use_usd_properties:
-            self.set_attrs(self.cfg.attrs, env_ids=local_env_ids)
+        self.set_attrs(self.cfg.attrs, env_ids=local_env_ids)
 
         pos = torch.as_tensor(
             self.cfg.init_pos, dtype=torch.float32, device=self.device

embodichain/lab/sim/sim_manager.py

@@ -1705,6 +1705,23 @@ def reset_objects_state(
             if uid not in excluded_uids:
                 sensor.reset(env_ids)
 
+    def export_usd(self, fpath: str) -> bool:
+        """Export the current simulation scene to a USD file.
+
+        Args:
+            fpath (str): The file path to save the USD file.
+
+        Returns:
+            bool: True if export is successful, False otherwise.
+        """
+        try:
+            self._env.export_to_usd_file(fpath)
+            logger.log_info(f"Simulation scene exported to USD file: {fpath}")
+            return True
+        except Exception as e:
+            logger.log_error(f"Failed to export simulation scene to USD: {e}")
+            return False
+
     def destroy(self) -> None:
         """Destroy all simulated assets and release resources."""
         # Clean up all gizmos before destroying the simulation

pyproject.toml

@@ -26,7 +26,7 @@ dynamic = ["version"]
 # Core install dependencies (kept from requirements.txt). Some VCS links are
 # specified using PEP 508 direct references where present.
 dependencies = [
-  "dexsim_engine==0.3.10",
+  "dexsim_engine==0.3.11",
   "setuptools>=78.1.1",
   "gymnasium>=0.29.1",
   "langchain",