Interactive Transform Gizmo

TODO: Add a screenshot or GIF of the transform gizmo in use in the viewport.

A transform gizmo — the click-and-drag handles for translating, rotating, and scaling objects in a 3D viewport — is one of the first things anyone reaches for when building a level editor. Bevy now has one built in, for your use today and our own use in the future.

Add TransformGizmoPlugin, mark a camera with TransformGizmoCamera, and tag entities with TransformGizmoFocus:

app.add_plugins(TransformGizmoPlugin);

commands.spawn((Camera3d::default(), TransformGizmoCamera));
commands.spawn((Mesh3d(mesh), TransformGizmoFocus));

The plugin is deliberately not connected to user input. This keeps the gizmo composable for editor authors who already have opinions about input handling. Sensitivity, snapping, and screen-space scaling are all configurable via TransformGizmoConfig, while modes are controlled via the TransformGizmoMode resource.

Much of the math and implementation strategy for this widget comes from the bevy_transform_gizmo crate. Thanks again to Foresight Spatial Labs for their generous open source contributions!