[example] Show in MuJoCo

Author: stephane-caron

CHANGELOG.md

@@ -17,6 +17,7 @@ This release adds 2 robot descriptions:
 - Example: load in Pinocchio
 - Example: load in PyBullet
 - Example: show in MeshCat
+- Example: show in MuJoCo
 - Example: show in PyBullet
 - Example: show in yourdfpy
 - New ``REPOSITORY_PATH`` member for each description

README.md

@@ -115,6 +115,7 @@ Load a robot description in:
 Visualize a robot description usingf:
 
 - [MeshCat](examples/show_in_meshcat.py)
+- [MuJoCo](examples/show_in_mujoco.py)
 - [PyBullet](examples/show_in_pybullet.py)
 - [yourdfpy](examples/show_in_yourdfpy.py)
 

examples/show_in_mujoco.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# Copyright 2022 Stéphane Caron
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Show a robot descriptions specified from the command line, using yourdfpy.
+
+This example requires MuJoCo, which is installed by ``pip install mujoco``, and
+the MuJoCo viewer installed by ``pip install mujoco-python-viewer``.
+"""
+
+import argparse
+from importlib import import_module  # type: ignore
+
+try:
+    import mujoco
+except ImportError as e:
+    raise ImportError("MuJoCo not found, try ``pip install mujoco``") from e
+
+try:
+    import mujoco_viewer
+except ImportError as e:
+    raise ImportError(
+        "MuJoCo viewer not found, " "try ``pip install mujoco-python-viewer``"
+    ) from e
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("name", help="name of the robot description")
+    args = parser.parse_args()
+
+    try:
+        module = import_module(f"robot_descriptions.{args.name}")
+    except ModuleNotFoundError:
+        module = import_module(f"robot_descriptions.{args.name}_description")
+
+    if not hasattr(module, "MJCF_PATH"):
+        raise ValueError(f"{args.name} is not an MJCF description")
+
+    model = mujoco.MjModel.from_xml_path(module.MJCF_PATH)
+    data = mujoco.MjData(model)
+
+    viewer = mujoco_viewer.MujocoViewer(model, data)
+    mujoco.mj_step(model, data)  # step at least once to load model in viewer
+    while viewer.is_alive:
+        viewer.render()
+    viewer.close()