From 76272a7fc2ffbf28016a5b65ccfbb375e829719f Mon Sep 17 00:00:00 2001
From: yuni <hut@hut.pm>
Date: Tue, 11 Jun 2024 00:05:03 +0200
Subject: [PATCH] add "target_velocity" var to handle_wants_maxvelocity()

---
 src/actor.rs | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/actor.rs b/src/actor.rs
index ed94544..483baeb 100644
--- a/src/actor.rs
+++ b/src/actor.rs
@@ -545,25 +545,32 @@ fn handle_wants_maxrotation(
     }
 }
 
+/// Slows down NPC's movement until they reach their target velocity.
 fn handle_wants_maxvelocity(
     time: Res<Time>,
     mut query: Query<(&mut LinearVelocity, &Engine, &WantsMaxVelocity)>,
 ) {
     let dt = time.delta_seconds();
     for (mut v, engine, maxv) in &mut query {
-        let total = v.0.length();
-        if total <= maxv.0 + EPSILON {
-            if total > maxv.0 {
-                v.0 = DVec3::splat(0.0);
+        let target_velocity = DVec3::splat(0.0);
+        let relative_velocity = v.0 - target_velocity;
+        let relative_speed = relative_velocity.length();
+
+        if relative_speed <= maxv.0 + EPSILON {
+            // it's already pretty close to the target
+            if relative_speed > maxv.0 {
+                // but not quite the target, so let's set it to the target
+                v.0 = target_velocity;
             }
         } else {
+            // slow it down a little bit
             // TODO: respect engine parameters for different thrusts for different directions
             let avg_thrust =
                 (engine.thrust_forward + engine.thrust_back + engine.thrust_sideways) / 3.0;
-            let acceleration = (avg_thrust * dt) as f64 * -v.0;
+            let acceleration = (avg_thrust * dt) as f64 * -relative_velocity;
             v.0 += acceleration;
             if v.0.length() + EPSILON < acceleration.length() {
-                v.0 = DVec3::splat(0.0);
+                v.0 = target_velocity;
             }
         }
     }