From a1e817f70a05283dcd98068dd616ffb6a70b7753 Mon Sep 17 00:00:00 2001
From: ghostly_zsh <ghostly@e3t.cc>
Date: Thu, 11 Jun 2026 12:05:45 -0500
Subject: [PATCH] netcode: readd interpolation

---
 crates/unified/src/client/interpolation.rs | 38 ++++++++++++++++++++++
 crates/unified/src/client/mod.rs           |  3 ++
 crates/unified/src/client/parts.rs         |  9 ++++-
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 crates/unified/src/client/interpolation.rs

diff --git a/crates/unified/src/client/interpolation.rs b/crates/unified/src/client/interpolation.rs
new file mode 100644
index 0000000000000000000000000000000000000000..065101db071c640ca6aa461d74641990f68921cb
--- /dev/null
+++ b/crates/unified/src/client/interpolation.rs
@@ -0,0 +1,38 @@
+use std::time::{Duration};
+use avian2d::parry::transformation::utils::transform;
+use crate::prelude::*;
+
+pub fn interpolation_plugin(app: &mut App) {
+    app
+        .add_systems(Update, update_interpolation_info)
+        .add_systems(Update, do_interpolation);
+}
+
+#[derive(Component, Debug)]
+pub struct TransformInterpolationInfo {
+    pub last_dt: Duration,
+    pub this_tick_start: bevy::platform::time::Instant,
+    pub latest_transform: Transform,
+    pub last_transform: Transform,
+}
+
+fn update_interpolation_info(
+    mut interpolation_query: Query<(&Transform, &mut TransformInterpolationInfo), Changed<Transform>>,
+    time: Res<Time>,
+) {
+    for (transform, mut info) in interpolation_query.iter_mut() {
+        info.last_dt = info.this_tick_start.elapsed();
+        info.this_tick_start = bevy::platform::time::Instant::now();
+        info.last_transform = info.latest_transform;
+        info.latest_transform = transform.clone();
+    }
+}
+fn do_interpolation(
+    mut interpolation_query: Query<(&mut Transform, &TransformInterpolationInfo)>,
+) {
+    for (mut transform, info) in &mut interpolation_query {
+        let dt = bevy::platform::time::Instant::now() - info.this_tick_start;
+        let progress = dt.as_secs_f32() / info.last_dt.as_secs_f32(); // should be between 0.0 and 1.0
+        transform.bypass_change_detection().translation = info.last_transform.translation + progress * (info.latest_transform.translation - info.last_transform.translation);
+    }
+}
\ No newline at end of file
diff --git a/crates/unified/src/client/mod.rs b/crates/unified/src/client/mod.rs
index ea59b3e05cdc3e324b71efba77164cee50f60261..e6c1afc0e78ffef9f101a5667f456de7d489d3f1 100644
--- a/crates/unified/src/client/mod.rs
+++ b/crates/unified/src/client/mod.rs
@@ -42,6 +42,7 @@ use std::rc::Rc;
 use wasm_bindgen::JsCast;
 #[cfg(target_arch = "wasm32")]
 use wasm_bindgen_futures::JsFuture;
+use crate::client::interpolation::interpolation_plugin;
 use crate::shared::config::planet::Planet;
 
 pub mod colors;
@@ -58,6 +59,7 @@ pub mod starguide;
 pub mod crafting;
 pub mod components;
 pub mod plugins;
+mod interpolation;
 
 pub struct ClientPlugin {
     pub server: Option<String>
@@ -81,6 +83,7 @@ impl Plugin for ClientPlugin {
             .add_plugins(starguide_input_plugin)
             //.add_plugins(starguide_orbit_plugin)
             .add_plugins(crafting_ui_plugin)
+            .add_plugins(interpolation_plugin)
             .add_systems(Update, find_me)
             .insert_state(GameplayState::Main)
             .insert_resource(DebugPickingMode::Disabled)
diff --git a/crates/unified/src/client/parts.rs b/crates/unified/src/client/parts.rs
index a78fd0d62ee3719846988939bb75e160534c842d..e0878d4b27983c90309e430b67a889c07e23b911 100644
--- a/crates/unified/src/client/parts.rs
+++ b/crates/unified/src/client/parts.rs
@@ -1,5 +1,5 @@
 use std::f32::consts::PI;
-
+use std::time::Duration;
 use crate::shared::attachment::{Joint, JointOf, Joints, PartInShip, Peer, SnapOf, SnapOfJoint};
 use crate::client::crafting::ui::open_crafting_ui;
 use crate::shared::ecs::Temperature;
@@ -11,6 +11,7 @@ use crate::client::components::Me;
 use crate::client::ship::attachment::AttachmentDebugRes;
 use crate::prelude::*;
 use bevy_replicon::client::confirm_history::ConfirmHistory;
+use crate::client::interpolation::TransformInterpolationInfo;
 
 pub fn parts_plugin(app: &mut App) {
     app.insert_resource(DragResource { dragged: None });
@@ -59,6 +60,12 @@ fn handle_incoming_parts(
             .insert(MAIN_LAYER)
             .insert(sprite)
             .insert(Pickable::default())
+            .insert(TransformInterpolationInfo {
+                last_dt: Duration::from_millis(50), // assume it was 20tps because we don't know
+                this_tick_start: bevy::platform::time::Instant::now(),
+                latest_transform: transform.clone(),
+                last_transform: transform.clone(),
+            })
             .observe(on_part_click)
             .observe(open_crafting_ui);
     }