From 3814aa415558e745d2fcacf81b31490b2bfdefa7 Mon Sep 17 00:00:00 2001
From: hut <hut@hut.pm>
Date: Mon, 13 May 2024 06:10:34 +0200
Subject: [PATCH] implement special relativity (for speed cheats only, so far)

---
 src/game.rs   | 14 ++++++++------
 src/nature.rs |  4 ++--
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/game.rs b/src/game.rs
index 5ee3351..4a7ba8f 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -136,13 +136,15 @@ fn handle_cheats(
         gforce.ignore_gforce_seconds = 1.0;
         v.0 = DVec3::ZERO;
     }
-    if key_input.pressed(settings.key_cheat_speed) {
+    if key_input.pressed(settings.key_cheat_speed) || key_input.pressed(settings.key_cheat_speed_backward) {
         gforce.ignore_gforce_seconds = 1.0;
-        v.0 += DVec3::from(trans.rotation * Vec3::new(0.0, 0.0, boost));
-    }
-    if key_input.pressed(settings.key_cheat_speed_backward) {
-        gforce.ignore_gforce_seconds = 1.0;
-        v.0 += DVec3::from(trans.rotation * Vec3::new(0.0, 0.0, -boost));
+        let sign = if key_input.pressed(settings.key_cheat_speed) { 1.0 } else { -1.0 };
+        let dv = DVec3::from(trans.rotation * Vec3::new(0.0, 0.0, sign * boost));
+        let current_speed = v.0.length();
+        let next_speed = (v.0 + dv).length();
+        let avg_speed = (current_speed + next_speed) / 2.0;
+        let inv_lorentz = nature::inverse_lorentz_factor(avg_speed.clamp(0.0, nature::C));
+        v.0 = v.0 + inv_lorentz * dv;
     }
     if key_input.just_pressed(settings.key_cheat_teleport) {
         if let Ok((transform, target_pos, target_v)) = q_target.get_single() {
diff --git a/src/nature.rs b/src/nature.rs
index 576cf0a..5704318 100644
--- a/src/nature.rs
+++ b/src/nature.rs
@@ -147,11 +147,11 @@ pub fn lorentz_factor_custom_c(speed: f64, c: f64) -> f64 {
 }
 
 pub fn inverse_lorentz_factor(speed: f64) -> f64 {
-    (1.0 - (speed.powf(2.0) / C.powf(2.0))).powf(0.5)
+    (1.0 - (speed.powf(2.0) / C.powf(2.0))).sqrt()
 }
 
 pub fn inverse_lorentz_factor_custom_c(speed: f64, c: f64) -> f64 {
-    (1.0 - (speed.powf(2.0) / c.powf(2.0))).powf(0.5)
+    (1.0 - (speed.powf(2.0) / c.powf(2.0))).sqrt()
 }
 
 pub fn simple_orbital_period(mass: f64, distance: f64) -> f64 {