From b708feba912edefe2c0b5ef37fceabc1cfeed0f0 Mon Sep 17 00:00:00 2001
From: ghostly_zsh <ghostly@e3t.cc>
Date: Thu, 10 Jul 2025 22:50:28 -0500
Subject: [PATCH] snap smoothing

---
 crates/unified/src/client/parts.rs | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/crates/unified/src/client/parts.rs b/crates/unified/src/client/parts.rs
index c70ed0680461760251ea2c23b9ff0b23ad6c1981..72ced353de1431c1daadc30d899146e3445e0b1d 100644
--- a/crates/unified/src/client/parts.rs
+++ b/crates/unified/src/client/parts.rs
@@ -81,6 +81,11 @@ struct SnapResource(Option<Entity>);
 
 #[derive(Component)]
 struct DragGhost;
+#[derive(Component)]
+struct GhostTarget(pub Quat);
+
+const TRANSLATION_SMOOTH: f32 = 0.3;
+const ROTATION_SMOOTH: f32 = 0.1;
 
 fn on_part_click(
     ev: Trigger<Pointer<Pressed>>,
@@ -96,7 +101,7 @@ fn on_part_click(
     };
     let mut s = sprite.0.clone();
     s.color = Color::srgba(0.7, 0.7, 0.7, 1.0);
-    commands.spawn((DragGhost, *sprite.1, s));
+    commands.spawn((DragGhost, GhostTarget(sprite.1.rotation), *sprite.1, s));
 
     drag.0 = Some(ev.target());
 }
@@ -139,7 +144,7 @@ fn on_part_release(
 /// This code is super cursed, and it will break at the lightest breeze
 fn update_drag_ghosts(
     mut ghost: Single<
-        &mut Transform,
+    (&mut Transform, &mut GhostTarget),
         (
             With<DragGhost>,
             Without<SnapOf>,
@@ -161,11 +166,12 @@ fn update_drag_ghosts(
 ) {
     const CUTOFF: f32 = 25.0; // px
 
+    let (mut ghost, mut ghost_target) = ghost.into_inner();
     let Some(cursor) = cursor.0 else { return };
 
     let mut best_distance = f32::INFINITY;
     let mut best_target = Transform::from_xyz(cursor.x, cursor.y, 0.0);
-    best_target.rotation = ghost.rotation;
+    best_target.rotation = ghost_target.0;
     let mut snap = None;
 
     for (snap_local_transform, snap_joint, snap_part, snap_id) in &snaps {
@@ -219,7 +225,7 @@ fn update_drag_ghosts(
 
         let target_transform = Transform {
             translation: joint_target,
-            rotation: ghost.rotation,
+            rotation: ghost_target.0,
             scale: offset.scale,
         };
         best_distance = distance_to_cursor;
@@ -228,18 +234,21 @@ fn update_drag_ghosts(
         snap = Some(snap_id);
     }
 
-    **ghost = best_target;
 
     if keys.pressed(KeyCode::KeyQ) {
-        ghost.rotation = ghost.rotation.mul_quat(Quat::from_rotation_z(
+        best_target.rotation = best_target.rotation.mul_quat(Quat::from_rotation_z(
             180.0_f32.to_radians() * time.delta_secs(),
         ));
     }
     if keys.pressed(KeyCode::KeyE) {
-        ghost.rotation = ghost.rotation.mul_quat(Quat::from_rotation_z(
+        best_target.rotation = best_target.rotation.mul_quat(Quat::from_rotation_z(
             -180.0_f32.to_radians() * time.delta_secs(),
         ));
     }
+    ghost_target.0 = best_target.rotation;
+    ghost.rotation = ghost.rotation.slerp(ghost_target.0, ROTATION_SMOOTH);
+    let dx = TRANSLATION_SMOOTH*(best_target.translation - ghost.translation);
+    ghost.translation += dx;
 
     rsnap.0 = snap;
 }