fix handle_wants_lookat() with ID_SPECIAL_PLAYERCAM

src/actor.rs

@@ -599,8 +599,9 @@ fn handle_wants_maxvelocity(
 }
 
 fn handle_wants_lookat(
-    mut query: Query<(&Position, &mut Rotation, &Transform, &WantsToLookAt)>,
+    mut query: Query<(&Position, &mut Rotation, &Transform, &WantsToLookAt), Without<Camera>>,
     q_playercam: Query<&Position, With<PlayerCamera>>,
+    q_cam: Query<&Transform, With<Camera>>,
     id2pos: Res<game::Id2Pos>,
 ) {
     let player_pos = if let Ok(player_pos) = q_playercam.get_single() {
@@ -608,17 +609,22 @@ fn handle_wants_lookat(
     } else {
         return;
     };
+    let cam_pos = if let Ok(cam_trans) = q_cam.get_single() {
+        cam_trans.translation.as_dvec3() + player_pos.0
+    } else {
+        return;
+    };
 
     // TODO: use ExternalTorque rather than hard-resetting the rotation
     for (pos, mut rot, trans, target_id) in &mut query {
-        let target_pos = if target_id.0 == cmd::ID_SPECIAL_PLAYERCAM {
+        let target_pos: DVec3 = if target_id.0 == cmd::ID_SPECIAL_PLAYERCAM {
-            player_pos
+            cam_pos
         } else if let Some(target_pos) = id2pos.0.get(&target_id.0) {
-            target_pos
+            *target_pos
         } else {
             continue;
         };
-        rot.0 = look_at_quat(**pos, *target_pos, trans.up().as_dvec3());
+        rot.0 = look_at_quat(**pos, target_pos, trans.up().as_dvec3());
     }
 }
 

src/common.rs

@@ -110,6 +110,10 @@ pub fn in_shadow(
 
 pub fn look_at_quat(from: DVec3, to: DVec3, up: DVec3) -> DQuat {
     let direction = (to - from).normalize();
+    let direction_len = direction.length_squared();
+    if direction_len < 1e-4 || direction_len.is_nan() {
+        return DQuat::IDENTITY;
+    }
     let right = up.cross(direction).normalize();
     let corrected_up = direction.cross(right);