run demo hello_motrixsim.py with error

[JacinteLYU]

Run in WSL2 with Ubuntu22.04：

Error information：

$ uv run hello_motrixsim.py
Motphys profiler initialized: disabled

thread '' panicked at /root/.cargo/registry/src/crates.mp-0edd756e2dd01b7c/bevy_winit-0.18.1/src/lib.rs:128:14:
Failed to build event loop: Os(OsError { line: 89, file: "/root/.cargo/registry/src/crates.mp-0edd756e2dd01b7c/winit-0.30.13/src/platform_impl/linux/wayland/event_loop/mod.rs", error: WaylandError(Connection(NoCompositor)) })
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
2026-06-03T14:05:55.648084Z ERROR motrix_render::platform::desktop: Render app thread panicked during shutdown: Any { .. }

[motphys-developers]

Thanks for reporting this.

This error is raised while RenderApp is creating the desktop window/event loop through winit:

WaylandError(Connection(NoCompositor))

So this is not caused by uv or the model file. It means the Ubuntu environment inside WSL2 does not currently have a usable Wayland compositor / WSLg GUI session available. hello_motrixsim.py opens an interactive render window, so it requires a working desktop GUI backend.

Could you please check whether WSLg GUI apps work in your WSL2 environment?

echo "WAYLAND_DISPLAY=$WAYLAND_DISPLAY"
echo "DISPLAY=$DISPLAY"
echo "XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR"
ls -la /mnt/wslg /mnt/wslg/runtime-dir 2>/dev/null

You can also test with a simple GUI app:

sudo apt update
sudo apt install -y x11-apps
xeyes

If xeyes cannot open a window either, MotrixSim's interactive RenderApp will not be able to open one in this WSL2 session.

On the Windows side, please also try updating/restarting WSL:

wsl --version
wsl --update
wsl --shutdown

As a temporary workaround, if X11 is available but Wayland is not, this may force the app away from the broken Wayland path:

env -u WAYLAND_DISPLAY uv run hello_motrixsim.py