Optimize unnecessary normalizations for Transform::local_{xyz} (#14171

)

Note that `GlobalTransform` already does it like this for `right`,
`left`, etc. so I didn't have to touch that one

crates/bevy_transform/src/components/transform.rs

@@ -222,8 +222,8 @@ impl Transform {
     /// Get the unit vector in the local `X` direction.
     #[inline]
     pub fn local_x(&self) -> Dir3 {
-        // Dir3::new(x) panics if x is of invalid length, but quat * unit vector is length 1
-        Dir3::new(self.rotation * Vec3::X).unwrap()
+        // Quat * unit vector is length 1
+        Dir3::new_unchecked(self.rotation * Vec3::X)
     }
 
     /// Equivalent to [`-local_x()`][Transform::local_x()]
@@ -241,8 +241,8 @@ impl Transform {
     /// Get the unit vector in the local `Y` direction.
     #[inline]
     pub fn local_y(&self) -> Dir3 {
-        // Dir3::new(x) panics if x is of invalid length, but quat * unit vector is length 1
-        Dir3::new(self.rotation * Vec3::Y).unwrap()
+        // Quat * unit vector is length 1
+        Dir3::new_unchecked(self.rotation * Vec3::Y)
     }
 
     /// Equivalent to [`local_y()`][Transform::local_y]
@@ -260,8 +260,8 @@ impl Transform {
     /// Get the unit vector in the local `Z` direction.
     #[inline]
     pub fn local_z(&self) -> Dir3 {
-        // Dir3::new(x) panics if x is of invalid length, but quat * unit vector is length 1
-        Dir3::new(self.rotation * Vec3::Z).unwrap()
+        // Quat * unit vector is length 1
+        Dir3::new_unchecked(self.rotation * Vec3::Z)
     }
 
     /// Equivalent to [`-local_z()`][Transform::local_z]