From b0fb81d88cd54680543ae32a81637ce97220ab40 Mon Sep 17 00:00:00 2001
From: sergeypdev <sergeypoznyak@protonmail.com>
Date: Sun, 27 Apr 2025 17:29:01 +0400
Subject: [PATCH] Increase lowest rpm to fix no torque when starting to go
 uphill

---
 game/game.odin               |  6 +++---
 game/physics/simulation.odin | 38 +++++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/game/game.odin b/game/game.odin
index ba36cd8..80679b7 100644
--- a/game/game.odin
+++ b/game/game.odin
@@ -266,7 +266,7 @@ update_runtime_world :: proc(runtime_world: ^Runtime_World, dt: f32) {
 			physics.Body_Config {
 				initial_pos = {0, 0, 0},
 				initial_rot = linalg.quaternion_from_euler_angle_x_f32(-10 * math.RAD_PER_DEG),
-				shape = physics.Shape_Box{size = {5, 1, 10}},
+				shape = physics.Shape_Box{size = {5, 1, 100}},
 			},
 		)
 
@@ -294,7 +294,7 @@ update_runtime_world :: proc(runtime_world: ^Runtime_World, dt: f32) {
 			},
 		)
 
-		if true {
+		if false {
 			for x in 0 ..< 10 {
 				for y in 0 ..< 10 {
 					physics.immediate_body(
@@ -412,7 +412,7 @@ update_runtime_world :: proc(runtime_world: ^Runtime_World, dt: f32) {
 			#hash("engine", "fnv32a"),
 			physics.Engine_Config {
 				rpm_torque_curve = assets.get_curve_2d(&g_mem.assetman, "assets/ae86_rpm_torque.csv").points,
-				lowest_rpm = 1000,
+				lowest_rpm = 1100,
 				inertia = 0.264,
 				internal_friction = 0.01,
 				gear_ratios = []f32{3.48, 3.587, 2.022, 1.384, 1, 0.861},
diff --git a/game/physics/simulation.odin b/game/physics/simulation.odin
index 7305809..a7ccd3e 100644
--- a/game/physics/simulation.odin
+++ b/game/physics/simulation.odin
@@ -655,6 +655,7 @@ pgs_solve_engines :: proc(sim_state: ^Sim_State, config: Solver_Config, dt: f32,
 					delta_omega := avg_wheel_vel * ratio - (-engine.w)
 
 					incremental_impulse := -inv_w * delta_omega
+					engine.axle.engine_impulse += incremental_impulse
 
 					engine.w += incremental_impulse * w1
 					wheel1.w += incremental_impulse * w2 * inv_ratio
@@ -682,6 +683,7 @@ pgs_solve_engines :: proc(sim_state: ^Sim_State, config: Solver_Config, dt: f32,
 					delta_omega := wheel2.w - wheel1.w
 
 					incremental_impulse := -inv_w * delta_omega
+					engine.axle.diff_impulse += incremental_impulse
 
 					wheel1.w += -incremental_impulse * wheel1.inv_inertia
 					wheel2.w += incremental_impulse * wheel2.inv_inertia
@@ -955,18 +957,36 @@ pgs_substep :: proc(
 
 				e.w += e.friction_impulse / e.inertia
 
-				if true {
+				// Warm start engine torque
+				if false {
+					drive_wheel1 := &e.axle.wheels[0]
+					wheel1 := get_suspension_constraint(sim_state, drive_wheel1.wheel)
+
+					drive_wheel2 := &e.axle.wheels[1]
+					wheel2 := get_suspension_constraint(sim_state, drive_wheel2.wheel)
+
+					gear_ratio := lookup_gear_ratio(gear_ratios, e.gear)
+
 					if e.gear != 0 {
-						for i in 0 ..< e.axle.wheel_count {
-							drive_wheel := &e.axle.wheels[i]
-							wheel := get_suspension_constraint(sim_state, drive_wheel.wheel)
+						ratio := gear_ratio * e.axle.final_drive_ratio
+						inv_ratio := f32(1.0 / (ratio))
 
-							ratio :=
-								lookup_gear_ratio(gear_ratios, e.gear) * e.axle.final_drive_ratio
-							inv_ratio := f32(1.0 / ratio)
+						w1 := f32(1.0 / (e.inertia * ratio * ratio))
+						w2 := wheel1.inv_inertia
+						w3 := wheel2.inv_inertia
 
-							wheel.w += drive_wheel.impulse * wheel.inv_inertia * inv_ratio
-							e.w += (drive_wheel.impulse / (e.inertia * ratio * ratio))
+						e.w += e.axle.engine_impulse * w1
+						wheel1.w += e.axle.engine_impulse * w2 * inv_ratio
+						wheel2.w += e.axle.engine_impulse * w3 * inv_ratio
+					}
+
+					// Warmp start diff impulse
+					if false {
+						switch e.axle.diff_type {
+						case .Open:
+						case .Fixed:
+							wheel1.w += -e.axle.diff_impulse * wheel1.inv_inertia
+							wheel2.w += e.axle.diff_impulse * wheel2.inv_inertia
 						}
 					}
 				}