change Transparent3d rangefinder to euclidean distance

crates/bevy_render/src/render_phase/rangefinder.rs

@@ -1,34 +1,28 @@
-use bevy_math::{Mat4, Vec3, Vec4};
+use bevy_math::{Mat4, Vec3};
 
 /// A distance calculator for the draw order of [`PhaseItem`](crate::render_phase::PhaseItem)s.
 pub struct ViewRangefinder3d {
-    view_from_world_row_2: Vec4,
+    translation: Vec3,
 }
 
 impl ViewRangefinder3d {
     /// Creates a 3D rangefinder for a view matrix.
     pub fn from_world_from_view(world_from_view: &Mat4) -> ViewRangefinder3d {
-        let view_from_world = world_from_view.inverse();
-
         ViewRangefinder3d {
-            view_from_world_row_2: view_from_world.row(2),
+            translation: world_from_view.col(3).truncate(),
         }
     }
 
-    /// Calculates the distance, or view-space `Z` value, for the given `translation`.
+    /// Calculates the distance for the given `translation`.
     #[inline]
     pub fn distance_translation(&self, translation: &Vec3) -> f32 {
-        // NOTE: row 2 of the inverse view matrix dotted with the translation from the model matrix
-        // gives the z component of translation of the mesh in view-space
-        self.view_from_world_row_2.dot(translation.extend(1.0))
+        - (*translation - self.translation).length_squared()
     }
 
-    /// Calculates the distance, or view-space `Z` value, for the given `transform`.
+    /// Calculates the distance for the given `transform`.
     #[inline]
     pub fn distance(&self, transform: &Mat4) -> f32 {
-        // NOTE: row 2 of the inverse view matrix dotted with column 3 of the model matrix
-        // gives the z component of translation of the mesh in view-space
-        self.view_from_world_row_2.dot(transform.col(3))
+        (transform.col(3).truncate() - self.translation).length_squared()
     }
 }