[bug/help needed] Rendering not following expected behaviour

Omniverse Isaac Sim
,
1

Hi guys,
so here is the situation:
I launch an app with the python.sh (following the simulation example ones)
Inside the python I do the following

CONFIG = {"display_options":3286, "width": 1280, "height": 720, "headless": args.headless}
kit = SimulationApp(launch_config=CONFIG)

enable some extensions

omni.usd.get_context().open_stage(env_path, None)

simulation_context = SimulationContext(physics_dt=1.0 / 200.0, rendering_dt=1.0 / 200.0, stage_units_in_meters=0.01)
simulation_context.start_simulation()
kit.update()

# set timeline of the experiment
timeline = omni.timeline.get_timeline_interface()
timeline.set_start_time(0.0)
timeline.set_end_time(args.experiment_length / 24.0)
fps = 24.0
timeline.set_time_codes_per_second(fps)

load a custom (simple) robot
attach 2 ROSBridgeCameras (NOT REB)

load another couple of objects

dynamic_prims = list of dynamic objects

while kit.is_running():
	# step the physics
	simulation_context.step(render=False)
	frame += 1
	if frame % 2 == 0:
		omni.kit.commands.execute("RosBridgeTickComponent", path="/ROS_Clock")
		
	# toggle the environment hiding objects
	status = not status
	utils.toggle_environment(status, dynamic_prims)
    simulation_context.render()

	# every two frames publish even cameras
	if frame % 2 == 0:
		for i, cam in enumerate(ros_camera_list):
			if i % 2 == 0:
# THIS PUBLISH ONLY ON EVEN CAMERAS
				omni.kit.commands.execute("RosBridgeTickComponent", path=str(cam.GetPath()))

	# # toggle the environment to YES show the moving objects
	status = not status
	utils.toggle_environment(status, dynamic_prims)
    simulation_context.render()

	if frame % 2 == 0:
		for i, cam in enumerate(ros_camera_list):
			if i % 2 == 1: 
# THIS PUBLISH ONLY ON ODD CAMERAS
				omni.kit.commands.execute("RosBridgeTickComponent", path=str(cam.GetPath()))

Problem is that the cameras sees randomly the objects that I am toggling (wrongly).

The simulation itself is running at 10FPS, and this might get even lower as I want very high resolution.

Isn’t render supposed to “hold” the execution until it is finished?
Is this ghosting normal or is there some setting that I need to set to avoid that?

I’ve noticed that, if I sleep after each render (let’s say more than 0.1s) this ghosting does not happen anymore (as the rendering do finish).

I’ve tried by attaching a callback to the render but that does not help either. (simulation_context.add_rendering_callback)

Best,
Elia

2

I might have found the problem.

Essentially render follows what is being specified by the rendering_dt. However, if the FPS for the current viewport is higher, this fails.

I have found a way to access the viewport fps, through

viewport.get_viewport_window().get_fps()

This, in my case, will output around 11, while if I query dt/fps from the kit update event I get 4 ms. (I increased the dt to 240 hz, so 1/240 actually is 4.smth)