Troubleshooting

Problems a game developer runs into, what causes them, and the fix. The Output Log is the first place to look: Rusteal logs under LogRusteal.

Building

rusteal build says the bindings have not been generated yet. The project was never built on this machine, or Rust/bindings/ was deleted. Run rusteal build --all.

The Unreal Build Tool says another instance is running. It runs one build at a time per engine: the editor compiling, or a build of another project. Wait for it to finish and build again.

Link errors in a generated wrapper after adding a module to rusteal.toml. A function the engine reflects but does not export. Add it to [codegen.blocklist] functions as "Class.Function" and run rusteal build --all.

The CLI refuses the project because of its version. The project and the CLI are at different Rusteal versions. See Versions and upgrades.

On Windows, Rust fails to link or the engine refuses the compiler. Check that Rust uses the MSVC host and that the Visual Studio components match the ones in Prerequisites.

In the editor

On Linux, the editor closes with a segfault in the NVIDIA driver, after a window closes or PIE stops. The crash report shows vkWaitForFences under FVulkanSwapChain::AcquireImageIndex, and the log has AcquireNextImage() failed due to the outdated swapchain just before. Run rusteal watch once, so it writes the platform optimizations, and restart the editor. If it happens in the Project Browser, before a project is open, add the line to the engine’s own config, as that page shows.

A Rust class does not show in the Place Actors panel or the class picker. The library did not load, or the class is not compiled in: check the Output Log for the library’s load messages and errors, and that the class’s module is declared in lib.rs (mod my_class;).

A change does not show after rusteal build. Check the Output Log for the reload. If Rusteal.AutoReload is 0, run Rusteal.Reload. A changed #[ustruct] needs a restart.

A value set in class_defaults does not apply to a Blueprint. The Blueprint child overrides it. In its Class Defaults, the value shows a reset arrow; click it to go back to the Rust default.

The Rust code of an event does not run. A Blueprint child that implements the same event in its graph replaces it. Remove the event node from the Blueprint, or give the Blueprint a BlueprintImplementableEvent of its own.

A Blueprint node is in error after a reload. The Rust function or property it used was removed or renamed. Fix the node or put the function back.

Playing

Input does nothing. The Output Log says which part is missing: no mapping contexts added (the player controller’s Blueprint child has none, or the game mode does not use that controller), or a function name in bind_action that does not exist. See Character movement and input.

spawn_actor logs that the actor has no root component. The spawned class has no scene component as root, so the transform is ignored. Give it a #[component(root)], or spawn a class that has one.

An engine call fails with ObjectDestroyed. The object was destroyed, or the reference was never set (a property the Blueprint child did not fill). Check the Blueprint’s Class Defaults, and handle the error where destruction is expected.

A panic message in the Output Log. Rust code panicked; the editor caught it and went on. The message and the location are in the log: fix the code and build again.

A StateTree logs that it could not find its context actor. It started before its controller possessed the pawn. Start it in the controller’s receive_possess. See AI.

Packaging

The packaged game misses an asset. Only Rust code loads it, by path. Add its directory to Additional Asset Directories to Cook. See Packaging a game.