Add option to only sync the state to improve sync performance in passive mode.

By default this option is off, which preserves the current behavior of syncing all of `mjModel` and `mjData`.

PiperOrigin-RevId: 776498017
Change-Id: I02127c9397efbabebb89b0e0d139b00b6e665d35

python/mujoco/simulate.cc

@@ -336,6 +336,7 @@ PYBIND11_MODULE(_simulate, pymodule) {
            CallIfNotNull(&mujoco::Simulate::LoadMessageClear),
            py::call_guard<py::gil_scoped_release>())
       .def("sync", CallIfNotNull(&mujoco::Simulate::Sync),
+           py::arg("state_only") = false,
            py::call_guard<py::gil_scoped_release>())
       .def("add_to_history", CallIfNotNull(&mujoco::Simulate::AddToHistory),
            py::call_guard<py::gil_scoped_release>())

python/mujoco/viewer.py

@@ -230,10 +230,10 @@ class Handle:
       return sim.lock()
     return contextlib.nullcontext()
 
-  def sync(self):
+  def sync(self, state_only: bool = False):
     sim = self._get_sim()
     if sim is not None:
-      sim.sync()  # locks internally
+      sim.sync(state_only)  # locks internally
 
   def update_hfield(self, hfieldid: int):
     sim = self._get_sim()