From 458e0005690ea9d579588a0a12368fc2c2c9a93a Mon Sep 17 00:00:00 2001
From: untodesu <kirill@untode.su>
Date: Tue, 1 Jul 2025 03:08:39 +0500
Subject: I hyper-focued on refactoring again - I put a cool-sounding "we are
 number one" remix on repeat and straight   up grinded the entire repository
 to a better state until 03:09 AM. I   guess I have something wrong in my
 brain that makes me do this shit

---
 game/client/entity/interpolation.cc | 63 +++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 game/client/entity/interpolation.cc

(limited to 'game/client/entity/interpolation.cc')

diff --git a/game/client/entity/interpolation.cc b/game/client/entity/interpolation.cc
new file mode 100644
index 0000000..6eb9e65
--- /dev/null
+++ b/game/client/entity/interpolation.cc
@@ -0,0 +1,63 @@
+#include "client/pch.hh"
+
+#include "client/entity/interpolation.hh"
+
+#include "core/math/constexpr.hh"
+
+#include "shared/entity/head.hh"
+#include "shared/entity/transform.hh"
+#include "shared/world/dimension.hh"
+
+#include "shared/coord.hh"
+
+#include "client/globals.hh"
+
+static void transform_interpolate(float alpha)
+{
+    auto group = globals::dimension->entities.group<entity::client::TransformIntr>(
+        entt::get<entity::Transform, entity::client::TransformPrev>);
+
+    for(auto [entity, interp, current, previous] : group.each()) {
+        interp.angles[0] = math::lerp(previous.angles[0], current.angles[0], alpha);
+        interp.angles[1] = math::lerp(previous.angles[1], current.angles[1], alpha);
+        interp.angles[2] = math::lerp(previous.angles[2], current.angles[2], alpha);
+
+        // Figure out previous chunk-local floating-point coordinates transformed
+        // to the current WorldCoord's chunk domain coordinates; we're interpolating
+        // against these instead of using previous.position.local to prevent jittering
+        auto previous_shift = coord::to_relative(current.chunk, current.local, previous.chunk, previous.local);
+        auto previous_local = current.local + previous_shift;
+
+        interp.chunk.x = current.chunk.x;
+        interp.chunk.y = current.chunk.y;
+        interp.chunk.z = current.chunk.z;
+
+        interp.local.x = math::lerp(previous_local.x, current.local.x, alpha);
+        interp.local.y = math::lerp(previous_local.y, current.local.y, alpha);
+        interp.local.z = math::lerp(previous_local.z, current.local.z, alpha);
+    }
+}
+
+static void head_interpolate(float alpha)
+{
+    auto group = globals::dimension->entities.group<entity::client::HeadIntr>(entt::get<entity::Head, entity::client::HeadPrev>);
+
+    for(auto [entity, interp, current, previous] : group.each()) {
+        interp.angles[0] = math::lerp(previous.angles[0], current.angles[0], alpha);
+        interp.angles[1] = math::lerp(previous.angles[1], current.angles[1], alpha);
+        interp.angles[2] = math::lerp(previous.angles[2], current.angles[2], alpha);
+
+        interp.offset.x = math::lerp(previous.offset.x, current.offset.x, alpha);
+        interp.offset.y = math::lerp(previous.offset.y, current.offset.y, alpha);
+        interp.offset.z = math::lerp(previous.offset.z, current.offset.z, alpha);
+    }
+}
+
+void entity::interpolation::update(void)
+{
+    if(globals::dimension) {
+        auto alpha = static_cast<float>(globals::fixed_accumulator) / static_cast<float>(globals::fixed_frametime_us);
+        transform_interpolate(alpha);
+        head_interpolate(alpha);
+    }
+}
\ No newline at end of file
-- 
cgit