Load scene by default for mj models and allow variants

Author: fabinsch

CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
 ### Added
 
 - Description: UFACTORY xArm7 (MJCF) (thanks to @kevinzakka)
+- Description: accept variant keyword for mujoco loader (thanks to @fabinsch)
 
 ### Changed
 

robot_descriptions/loaders/mujoco.py

@@ -17,6 +17,7 @@
 def load_robot_description(
     description_name: str,
     commit: Optional[str] = None,
+    variant: Optional[str] = "scene",
 ) -> mujoco.MjModel:
     """Load a robot description in MuJoCo.
 
@@ -35,5 +36,19 @@ def load_robot_description(
         os.environ.pop("ROBOT_DESCRIPTION_COMMIT", None)
     if not hasattr(module, "MJCF_PATH"):
         raise ValueError(f"{description_name} is not an MJCF description")
-
-    return mujoco.MjModel.from_xml_path(module.MJCF_PATH)
+    
+    def load_model_from_path(path):
+        try:
+            return mujoco.MjModel.from_xml_path(path)
+        except ValueError:
+            print(f"{path} not found. Loading default robot model.")
+            return None
+    model_path = module.MJCF_PATH
+    if variant is not None:
+        path_parts = model_path.split(os.sep)
+        path_parts[-1] = f"{variant}.xml"
+        variant_path = os.sep.join(path_parts)
+        model = load_model_from_path(variant_path)
+        if model: 
+            return model
+    return load_model_from_path(model_path)