Viewport

HoloOcean simulations are run in a pop-up window known as the “viewport”.

Hotkeys

There are a few hotkeys you can use to control the viewport when the window is open and the environment is being ticked (with calls to tick() or step()).

The “AgentFollower”, or the camera that the viewport displays, can be manipulated as follows:

Key	Action	Description
`c`	Toggle camera mode	Toggles the camera from a chase camera and perspective camera, which shows what the agent’s camera sensor sees.
`v`	Toggle spectator mode	Toggles spectator mode, which allows you to free-cam around the world with the mouse or WASD commands.
`w` `a` `s` `d`	Move camera	Move the viewport camera around when in spectator/free-cam mode.
`q` `ctrl`	Descend	For spectator/free-cam mode
`e` `space`	Ascend	For spectator/free-cam mode
`shift`	Turbo	Move faster when in spectator/free-cam
`tab`	Cycle through agents	When not in spectator/free-cam mode, cycles through the agents in the world
`h`	Toggle HUD	The HUD displays the name and location of the agent the viewport is following, or the location of the camera if the viewport is detached (spectator mode) Note that this will interfere with the ViewportCapture sensor

Opening Console

Pressing ~ will open Unreal Engine 5’s developer console, which has a few useful commands. See the Unreal Docs for a complete list of commands.

Useful Commands

stat fps Prints the frames per second on the screen.

Using HoloOcean Headless

On Linux, HoloOcean can run headless without opening a viewport window. This can happen automatically, or you can force it to not appear.

Headless Mode vs Disabling Viewport Rendering

These are two different features.

Disabling Viewport Rendering is calling the (should_render_viewport()) method on a HoloOceanEnvironment. This can be done at runtime. It will appear as if the image being rendered in the viewport has frozen, but cameras other sensors will still update correctly.

Headless Mode is when the viewport window does not appear. If Headless Mode is manually enabled, it will also disable viewport rendering automatically.

Forcing Headless Mode

In holoocean.make(), set show_viewport to False.

Note

This will also disable viewport rendering (should_render_viewport())

If you still want to render the viewport (ie for the ViewportCapture) when running headless, simply set (should_render_viewport()) to True

Automatic Headless Mode

If the engine does not detect the DISPLAY environment variable, it will not open a window. This will happen automatically if HoloOcean is run from a SSH session.

Note

This will not disable viewport rendering, meaning the simulaito nwill still be generating the displayed images, but they will not be displayed. When running over an SSH session, be sure to manually disable viewport rendering to avoid wasting resources.