1. Handles are wrapped in components now

https://github.com/bevyengine/bevy/pull/15524

Handle<Scene> → SceneRoot( Handle<Scene> )

Handle<Mesh> → Mesh3d( Handle<Mesh> )

Handle<Material<T>> → MeshMaterial3d( Handle<Material<T>> )

1. SceneInstanceReady is a trigger with instance_id now !! (no more event.parent prop..)

Use SceneInstanceReady as trigger ! Not as an event .read() …

(This means they will be ‘pushed’ instead of ‘polled’ )

.add_observer(handle_material_overrides_when_scene_ready)

...

fn handle_material_overrides_when_scene_ready(	 
	scene_instance_evt_trigger: Trigger<SceneInstanceReady>  ,
	  material_override_request_query: Query<&MaterialOverrideWhenSceneReadyComponent >,
	mut commands: Commands, 
 	parent_query : Query<&Parent>, 
){  
	let trig_entity = scene_instance_evt_trigger.entity();

	let Some(parent_entity) = parent_query.get(trig_entity).ok().map( |p| p.get() ) else {return};

 	// need to check parent !? 
	 let Some(mat_override_request) = material_override_request_query.get(parent_entity).ok() else {return};
 	
         let material_override = mat_override_request.material_override.clone() ;

 				if let Some(mut cmd) = commands.get_entity( trig_entity ) {

 					cmd.try_insert(  
 						MaterialOverrideComponent {
 							material_override 
 						}
 					);
 				} 

}

1. Cursor Ray is vendored into bevy0.15 now ! Use this example, its quite easy to migrate BUT cursor ray requires an iter() now instead of a let Some() since it can operate on multiple viewports/cameras at once now.

https://github.com/bevyengine/bevy/blob/main/examples/3d/mesh_ray_cast.rs