Render() should be called after engine.after_step() to make sure cons…

…istency (#608)

* move render to after_step to ensure consistency

* format

metadrive/engine/base_engine.py

@@ -439,10 +439,6 @@ def step(self, step_num: int = 1) -> None:
 
             if self.force_fps.real_time_simulation and i < step_num - 1:
                 self.task_manager.step()
-        #  panda3d render and garbage collecting loop
-        self.task_manager.step()
-        if self.on_screen_message is not None:
-            self.on_screen_message.render()
 
     def after_step(self, *args, **kwargs) -> Dict:
         """

metadrive/envs/base_env.py

@@ -457,6 +457,12 @@ def _step_simulator(self, actions):
         self.engine.step(self.config["decision_repeat"])
         # update states, if restore from episode data, position and heading will be force set in update_state() function
         scene_manager_after_step_infos = self.engine.after_step()
+
+        #  Do rendering
+        self.engine.task_manager.step()
+        if self.engine.on_screen_message is not None:
+            self.engine.on_screen_message.render()
+
         # Note that we use shallow update for info dict in this function! This will accelerate system.
         return merge_dicts(
             scene_manager_after_step_infos, scene_manager_before_step_infos, allow_new_keys=True, without_copy=True

metadrive/tests/vis_env/vis_nuscenes.py

@@ -21,7 +21,7 @@
             # "need_lane_localization": False,
             # "image_observation": True,
             "show_logo": False,
-            "no_traffic": True,
+            "no_traffic": False,
             "store_data": False,
             "sequential_seed": True,
             # "pstats": True,