From 91d19e94a03a4bb98e4731cafb2dfef816be3678 Mon Sep 17 00:00:00 2001
From: yuni <hut@hut.pm>
Date: Thu, 23 May 2024 00:31:31 +0200
Subject: [PATCH] implement preferred looking direction for NPCs

---
 src/actor.rs      | 19 +++++++++++++++++++
 src/cmd.rs        |  9 +++++++++
 src/common.rs     | 10 ++++++++++
 src/data/defs.txt |  5 +++++
 4 files changed, 43 insertions(+)

diff --git a/src/actor.rs b/src/actor.rs
index f5281d2..1ca5657 100644
--- a/src/actor.rs
+++ b/src/actor.rs
@@ -32,6 +32,7 @@ impl Plugin for ActorPlugin {
                 update_power,
                 handle_wants_maxrotation,
                 handle_wants_maxvelocity,
+                handle_wants_lookat,
             ),
         );
         app.add_systems(
@@ -153,6 +154,8 @@ pub struct WantsMaxRotation(pub f64);
 #[derive(Component)]
 pub struct WantsMaxVelocity(pub f64);
 #[derive(Component)]
+pub struct WantsToLookAt(pub String);
+#[derive(Component)]
 pub struct Identifier(pub String);
 
 #[derive(Component)]
@@ -556,6 +559,22 @@ fn handle_wants_maxvelocity(
     }
 }
 
+fn handle_wants_lookat(
+    mut query: Query<(
+        &Position,
+        &mut Rotation,
+        &mut ExternalTorque,
+        &WantsToLookAt,
+    )>,
+    id2pos: Res<game::Id2Pos>,
+) {
+    for (pos, mut rot, mut _torque, target_id) in &mut query {
+        if let Some(target_pos) = id2pos.0.get(&target_id.0) {
+            rot.0 = look_at_quat(**pos, *target_pos, DVec3::Y);
+        }
+    }
+}
+
 fn handle_damage(
     mut ew_playerdies: EventWriter<game::PlayerDiesEvent>,
     mut q_hp: Query<(&mut HitPoints, Option<&Player>), Changed<HitPoints>>,
diff --git a/src/cmd.rs b/src/cmd.rs
index 873b05d..c8546c8 100644
--- a/src/cmd.rs
+++ b/src/cmd.rs
@@ -84,6 +84,7 @@ struct ParserState {
     has_ring: bool,
     wants_maxrotation: Option<f64>,
     wants_maxvelocity: Option<f64>,
+    wants_tolookat_id: Option<String>,
     collider_is_mesh: bool,
     collider_is_one_mesh_of_scene: bool,
     thrust_forward: f32,
@@ -140,6 +141,7 @@ impl Default for ParserState {
             has_ring: false,
             wants_maxrotation: None,
             wants_maxvelocity: None,
+            wants_tolookat_id: None,
             collider_is_mesh: false,
             collider_is_one_mesh_of_scene: false,
             thrust_forward: default_engine.thrust_forward,
@@ -503,6 +505,10 @@ pub fn load_defs(mut ew_spawn: EventWriter<SpawnEvent>) {
                     continue;
                 }
             }
+            ["wants", "lookat", id] => {
+                // NOTE: Will not work if the actor has no engine
+                state.wants_tolookat_id = Some(id.to_string());
+            }
             ["armodel", asset_name] => {
                 state.ar_model = Some(asset_name.to_string());
             }
@@ -714,6 +720,9 @@ fn spawn_entities(
                 if let Some(value) = state.wants_maxvelocity {
                     actor.insert(actor::WantsMaxVelocity(value));
                 }
+                if let Some(value) = &state.wants_tolookat_id {
+                    actor.insert(actor::WantsToLookAt(value.clone()));
+                }
                 if let Some(color) = state.light_color {
                     actor.insert((
                         PointLight {
diff --git a/src/common.rs b/src/common.rs
index a9490b0..85b3f12 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -107,3 +107,13 @@ pub fn in_shadow(
 
     return closest_vector.length() < max_distance;
 }
+
+pub fn look_at_quat(from: DVec3, to: DVec3, up: DVec3) -> DQuat {
+    let direction = (to - from).normalize();
+    let right = up.cross(direction).normalize();
+    let corrected_up = direction.cross(right);
+
+    let mat3 = bevy::math::DMat3::from_cols(right, corrected_up, direction);
+
+    DQuat::from_mat3(&mat3)
+}
diff --git a/src/data/defs.txt b/src/data/defs.txt
index 1b6f41f..fc8e102 100644
--- a/src/data/defs.txt
+++ b/src/data/defs.txt
@@ -459,6 +459,7 @@ actor -3300 10 0 pizzeria
         angularmomentum 0 0 0
         wants maxrotation 0
         wants maxvelocity 0
+        wants lookat player
         thrust 15 6 3 400 0.5
         rotationy -126
         scale 3
@@ -475,6 +476,7 @@ actor -3300 10 0 pizzeria
         thrust 1.2 1 1 20 1.5
         wants maxrotation 0
         wants maxvelocity 0
+        wants lookat player
         rotationy -90
         angularmomentum 0 0 0
         pronoun he
@@ -533,6 +535,7 @@ actor 100 -18000 2000 clippy
     angularmomentum 0 0 0
     wants maxrotation 0
     wants maxvelocity 0
+    wants lookat player
     thrust 15 6 3 400 0.5
     pointofinterest yes
     rotationy -90
@@ -684,6 +687,7 @@ actor -184971e3 149410e3 -134273e3 clippy
     angularmomentum 0 0 0
     wants maxrotation 0
     wants maxvelocity 0
+    wants lookat player
     thrust 15 6 3 400 0.5
     pointofinterest yes
     rotationy -90
@@ -828,6 +832,7 @@ actor 0 -44e3 0 clippy
     angularmomentum 0 0 0
     wants maxrotation 0
     wants maxvelocity 0
+    wants lookat player
     thrust 15 6 3 400 0.5
     pointofinterest yes
     rotationy -90