From 0f7603d3cb3c722c9cbe29769bd71bb17fed5ff7 Mon Sep 17 00:00:00 2001
From: Josh Creek <8179928+jcreek@users.noreply.github.com>
Date: Wed, 5 Aug 2026 09:13:52 +0100
Subject: [PATCH] fix(ship): delta-scale drag so it stays correct at any
 physics tick rate

drag_coefficient/angular_drag/the idle angular-drag multiplier were applied
once per physics tick with no delta scaling, correct only because
project.godot never pins physics/common/physics_ticks_per_second and
Godot's default happens to be 60. _tick_scaled(k, state.step) makes the
decay rate invariant to tick rate instead. Also promotes the previously
hardcoded 0.9 idle angular-drag literal to an export, matching its sibling.
---
 Game/scripts/ship.gd | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/Game/scripts/ship.gd b/Game/scripts/ship.gd
index e1310025..788faeee 100644
--- a/Game/scripts/ship.gd
+++ b/Game/scripts/ship.gd
@@ -18,6 +18,7 @@ extends RigidBody3D
 @export var max_angular_speed = 3.0      # Maximum rotation speed
 @export var drag_coefficient = 0.98      # Linear drag (air resistance)
 @export var angular_drag = 0.95          # Rotational drag
+@export var idle_angular_drag = 0.9      # Rotational drag when no rotation input is held
 
 @export_group("Surface Pull")
 @export var wall_pull_strength = 6.0     # Wall grav-plating strength (m/s^2-equivalent)
@@ -279,12 +280,22 @@ func apply_rotation_forces(state: PhysicsDirectBodyState3D, rotation_input: Vect
 	state.apply_torque(torque)
 
 
+# Scales a per-tick decay multiplier `k` (defined at a 60 Hz reference rate)
+# by the actual elapsed tick time `step`, so `v *= _tick_scaled(k, step)`
+# decays at the same rate per second regardless of physics_ticks_per_second.
+func _tick_scaled(k: float, step: float) -> float:
+	return pow(k, step * 60.0)
+
+
 func apply_drag_and_limits(state: PhysicsDirectBodyState3D, rotation_input: Vector3):
 	# Linear drag (air resistance)
 	# Physics: F_drag = -½ * ρ * v² * C_d * A (drag force equation)
 	# Simplified: v_new = v_old * drag_coefficient (exponential decay)
-	# This simulates air resistance reducing velocity over time
-	state.linear_velocity *= drag_coefficient
+	# This simulates air resistance reducing velocity over time.
+	# _tick_scaled makes the decay rate invariant to the physics tick rate —
+	# drag_coefficient/angular_drag/idle_angular_drag are all defined as the
+	# per-tick multiplier at a 60 Hz reference rate.
+	state.linear_velocity *= _tick_scaled(drag_coefficient, state.step)
 
 	# Angular drag (rotational resistance)
 	# Physics: Similar to linear drag but for rotational motion
@@ -292,10 +303,10 @@ func apply_drag_and_limits(state: PhysicsDirectBodyState3D, rotation_input: Vect
 	# Simplified: ω_new = ω_old * angular_drag (exponential decay)
 	if rotation_input.length() < 0.01:
 		# More drag when not actively rotating to stop quicker
-		state.angular_velocity *= 0.9
+		state.angular_velocity *= _tick_scaled(idle_angular_drag, state.step)
 	else:
 		# Normal drag when actively rotating
-		state.angular_velocity *= angular_drag
+		state.angular_velocity *= _tick_scaled(angular_drag, state.step)
 
 	# Limit maximum speeds
 	# Physics: Terminal velocity concept - maximum achievable speed