From b700e0fe248c504bf7310e0a0a9e4443d5f67815 Mon Sep 17 00:00:00 2001
From: hut <hut@hut.pm>
Date: Fri, 5 Apr 2024 20:57:21 +0200
Subject: [PATCH] implement matching velocity with targeted object

---
 README.md     |  2 +-
 src/camera.rs | 20 ++++++++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 33fbf23..b4f052d 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Links:
 
 # Key Bindings
 
-- Space: Slow down
+- Space: Slow down (or match velocity)
 - AWSD/Shift/Ctrl: Accelerate
 - R: Rotate (hold & move mouse)
 - E: Interact: Talk to people, enter vehicles
diff --git a/src/camera.rs b/src/camera.rs
index 2d5c2dc..58f5f9f 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -8,7 +8,7 @@ use bevy::transform::TransformSystem;
 use bevy::math::{DVec3, DQuat};
 use bevy_xpbd_3d::prelude::*;
 use std::f32::consts::PI;
-use crate::{actor, audio, settings};
+use crate::{actor, audio, hud, settings};
 
 pub struct CameraPlugin;
 
@@ -151,6 +151,7 @@ fn apply_input_to_player(
     rocket_sound_controller: Query<&AudioSink, With<audio::ComponentRocketSound>>,
     ion_sound_controller: Query<&AudioSink, With<audio::ComponentIonSound>>,
     electricmotor_sound_controller: Query<&AudioSink, With<audio::ComponentElectricMotorSound>>,
+    q_target: Query<&LinearVelocity, (With<hud::IsTargeted>, Without<actor::PlayerCamera>)>,
     mut q_playercam: Query<(
             &Transform,
             &mut actor::Engine,
@@ -169,6 +170,12 @@ fn apply_input_to_player(
         focused = window_result.unwrap().focused;
     }
 
+    let target_v: DVec3 = if let Ok(target) = q_target.get_single() {
+        target.0
+    } else {
+        DVec3::splat(0.0)
+    };
+
     if let Ok((player_transform, mut engine, mut angularvelocity, mut v, mut torque)) = q_playercam.get_single_mut() {
         // Handle key input
         if focused {
@@ -191,7 +198,7 @@ fn apply_input_to_player(
                 axis_input.y -= 1.2;
             }
             if key_input.pressed(settings.key_stop) {
-                let stop_direction = -v.normalize();
+                let stop_direction = (target_v - v.0).normalize();
                 if stop_direction.length_squared() > 0.3 {
                     axis_input += 1.0 * DVec3::from(player_transform.rotation.inverse() * stop_direction.as_vec3());
                 }
@@ -220,13 +227,14 @@ fn apply_input_to_player(
             let threshold = 1e-5;
             if key_input.pressed(settings.key_stop) {
                 // Decelerate
+                let dv = target_v - v.0;
                 for i in 0..3 {
-                    if v[i].abs() < threshold {
-                        v[i] = 0.0;
+                    if dv[i].abs() < threshold {
+                        v[i] = target_v[i];
                     }
-                    else if v[i].signum() != (v[i] + acceleration_total[i]).signum() {
+                    else if dv[i].signum() != (dv[i] + acceleration_total[i]).signum() {
                         // Almost stopped, but we overshot v=0
-                        v[i] = 0.0;
+                        v[i] = target_v[i];
                         acceleration_total[i] = 0.0;
                     }
                 }