working on examples of transform utilities

crates/bevy_xr_utils/src/transform_utils.rs

@@ -0,0 +1,59 @@
+use bevy::prelude::*;
+use bevy_openxr::{helper_traits::{ToQuat, ToVec3}, init::OxrTrackingRoot, resources::OxrViews};
+
+pub struct TransformUtilitiesPlugin;
+
+impl Plugin for TransformUtilitiesPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_event::<SnapToRotation>();
+        app.add_event::<SnapToPosition>();
+        app.add_systems(PostUpdate, handle_transform_events);
+    }
+}
+
+//events
+#[derive(Event, Debug)]
+pub struct SnapToRotation(pub Quat);
+
+#[derive(Event, Debug)]
+pub struct SnapToPosition(pub Vec3);
+
+pub fn handle_transform_events(
+    mut root_query: Query<&mut Transform, With<OxrTrackingRoot>>,
+    views: ResMut<OxrViews>,
+    mut position_reader: EventReader<SnapToPosition>,
+    mut rotation_reader: EventReader<SnapToRotation>,
+) {
+    let result = root_query.get_single_mut();
+    match result {
+        Ok(mut root_transform) => {
+            //rotation first
+            let view = views.first();
+            match view {
+                Some(view) => {
+                    //get our parameters together
+                    let mut view_translation = view.pose.position.to_vec3();
+                    let view_quat = view.pose.orientation.to_quat();
+                    let view_yaw = view_quat.to_euler(EulerRot::XYZ).1;
+                    let science = Quat::from_axis_angle(*root_transform.up(), view_yaw);
+                    let invert_science = science.inverse();
+                    view_translation.y = 0.0; //we want to do rotations around the same height as the root
+                    let root_local = root_transform.translation;
+                    let view_global = root_transform.rotation.mul_vec3(view_translation) + root_local;
+                    //now set our rotation for every event, this does mean only the last event matters
+                    for snap in rotation_reader.read() {
+                        let rotation_quaternion = snap.0.mul_quat(invert_science);
+                        root_transform.rotate_around(view_global, rotation_quaternion);
+                    }
+                    //position second
+                    for position in position_reader.read() {
+                        root_transform.translation = position.0;
+                    }
+                    
+                },
+                None => debug!("error getting first view"),
+            }
+        }
+        Err(_) => debug!("error getting root transform"),
+    }
+}