Add update_{hfield,mesh,texture} methods to the passive viewer.

Fixes #812.
Fixes #958.
Fixes #965.

PiperOrigin-RevId: 548181282
Change-Id: I6eb0cd2ce52c66083e83dd08d69e0cfb4178dbba

python/mujoco/simulate.cc

@@ -154,6 +154,18 @@ PYBIND11_MODULE(_simulate, pymodule) {
             simulate.uiloadrequest.fetch_sub(1);
           },
           py::call_guard<py::gil_scoped_release>())
+      .def(
+          "update_hfield",
+          [](SimulateWrapper& simulate, int hfieldid) {
+            simulate.UpdateHField(hfieldid);
+          },
+          py::call_guard<py::gil_scoped_release>())
+      .def(
+          "update_texture",
+          [](SimulateWrapper& simulate, int texid) {
+            simulate.UpdateTexture(texid);
+          },
+          py::call_guard<py::gil_scoped_release>())
 
       .def_property(
           "droploadrequest",

python/mujoco/viewer.py

@@ -113,8 +113,22 @@ class Handle:
   def sync(self):
     sim = self._sim()
     if sim is not None:
-      with sim.lock():
-        sim.sync()
+      sim.sync()  # locks internally
+
+  def update_hfield(self, hfieldid: int):
+    sim = self._sim()
+    if sim is not None:
+      sim.update_hfield(hfieldid)  # locks internally and blocks until done
+
+  def update_mesh(self, meshid: int):
+    sim = self._sim()
+    if sim is not None:
+      sim.update_mesh(meshid)  # locks internally and blocks until done
+
+  def update_texture(self, texid: int):
+    sim = self._sim()
+    if sim is not None:
+      sim.update_texture(texid)  # locks internally and blocks until done
 
   def __enter__(self):
     return self