From f682f1d6c003c39fb6b6d537045ab787b8edd33c Mon Sep 17 00:00:00 2001
From: hut <hut@hut.pm>
Date: Fri, 5 Apr 2024 22:06:58 +0200
Subject: [PATCH] allow reuse of angular diameter calculation code

---
 src/camera.rs | 50 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index 58f5f9f..d4efda2 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -344,6 +344,7 @@ fn apply_input_to_player(
 }
 
 // Find the closest world object that the player is looking at
+#[inline]
 pub fn find_closest_target<TargetSpecifier>(
     objects: Vec<(TargetSpecifier, &Transform)>,
     camera_transform: &Transform,
@@ -352,24 +353,13 @@ pub fn find_closest_target<TargetSpecifier>(
 {
     let mut closest_entity: Option<TargetSpecifier> = None;
     let mut closest_distance: f32 = f32::MAX;
-    let target_vector = (camera_transform.rotation * Vec3::new(0.0, 0.0, -1.0))
+    let target_vector: Vec3 = (camera_transform.rotation * Vec3::new(0.0, 0.0, -1.0))
         .normalize_or_zero();
     for (entity, trans) in objects {
         // Use Transform instead of Position because we're basing this
         // not on the player mesh but on the camera, which doesn't have a position.
-        let pos_vector = (trans.translation - camera_transform.translation)
-            .normalize_or_zero();
-        let cosine_of_angle = target_vector.dot(pos_vector);
-        let angle = cosine_of_angle.acos();
-        let distance = trans.translation.distance(camera_transform.translation);
-        let leeway = 1.3;
-        let angular_diameter = if distance > 0.0 {
-            // Angular Diameter
-            leeway * (trans.scale[0] / distance).asin()
-        }
-        else {
-            0.0
-        };
+        let (angular_diameter, angle, distance) = calc_angular_diameter_known_target_vector(
+                trans, camera_transform, &target_vector);
         if angle <= angular_diameter.clamp(0.001, PI) {
             // It's in the field of view!
             //commands.entity(entity).insert(IsTargeted);
@@ -381,3 +371,35 @@ pub fn find_closest_target<TargetSpecifier>(
     }
     return (closest_entity, closest_distance);
 }
+
+#[inline]
+pub fn calc_angular_diameter_known_target_vector(
+    target: &Transform,
+    camera: &Transform,
+    target_vector: &Vec3,
+) -> (f32, f32, f32) {
+    let pos_vector: Vec3 = (target.translation - camera.translation)
+        .normalize_or_zero();
+    let cosine_of_angle: f32 = target_vector.dot(pos_vector);
+    let angle: f32 = cosine_of_angle.acos();
+    let distance: f32 = target.translation.distance(camera.translation);
+    let leeway: f32 = 1.3;
+    let angular_diameter: f32 = if distance > 0.0 {
+        // Angular Diameter
+        leeway * (target.scale[0] / distance).asin()
+    }
+    else {
+        0.0
+    };
+    return (angular_diameter, angle, distance);
+}
+
+#[inline]
+pub fn calc_angular_diameter(
+    target: &Transform,
+    camera: &Transform,
+) -> (f32, f32, f32) {
+    let target_vector: Vec3 = (camera.rotation * Vec3::new(0.0, 0.0, -1.0))
+        .normalize_or_zero();
+    return calc_angular_diameter_known_target_vector(target, camera, &target_vector);
+}