From d284853f24a511f4407ad40920e75953711670a5 Mon Sep 17 00:00:00 2001
From: fnicon <mybeddrom@gmail.com>
Date: Sat, 21 Mar 2026 00:28:21 +0900
Subject: [PATCH] update racing physics

---
 game/love_src/src/system/racing_phy.lua       | 40 ++++++++++++--
 .../love_src/src/world/top_down_race/init.lua |  8 +--
 .../world/top_down_race/system/velocity.lua   | 54 ++++++++++++-------
 3 files changed, 75 insertions(+), 27 deletions(-)

diff --git a/game/love_src/src/system/racing_phy.lua b/game/love_src/src/system/racing_phy.lua
index 970f94f..465fdde 100644
--- a/game/love_src/src/system/racing_phy.lua
+++ b/game/love_src/src/system/racing_phy.lua
@@ -13,13 +13,47 @@ local function accelerate(dt, gas_input, speed, max_speed, accel, min_speed)
   return new_speed
 end
 
-local function drift(dt, pos_x, speed, max_speed, curve, centrifugal)
+local function centrifugal_force(dt, speed, max_speed)
+  local speed_percent = (speed/max_speed)
+  local dx = dt * 2 * speed_percent
+  local dy = dt * 2 * speed_percent
+  -- assume mass is 1
+  return 1 * dy * speed * speed
+end
+
+local function drift(dt, pos_x, pos_y, speed, max_speed, angle, centrifugal)
   local speed_percent = (speed/max_speed)
   local dx = dt * 2 * speed_percent -- at top speed, should be able to cross from left to right (-1 to 1) in 1 second
-  return pos_x - (dx * speed_percent * curve * centrifugal);
+  local dy = dt * 2 * speed_percent
+  cos = math.cos(angle)
+  sin = math.sin(angle)
+
+  return pos_x + (dx * speed_percent * cos * centrifugal),
+    pos_y + (dy * speed_percent * sin * centrifugal)
+end
+
+local function gas(accel, drag)
+  return accel - drag
+end
+
+local function brake(decel, drag, grip)
+  return - decel - drag - grip
+end
+
+local function roam(decel, drag)
+  return - decel - drag
+end
+
+local function steer(_steer, grip, drag, velocity)
+  return _steer + grip + drag - velocity
 end
 
 return {
   accelerate = accelerate,
-  drift = drift
+  drift = drift,
+  gas = gas,
+  brake = brake,
+  steer = steer,
+  roam = roam,
+  centrifugal_force = centrifugal_force
 }
diff --git a/game/love_src/src/world/top_down_race/init.lua b/game/love_src/src/world/top_down_race/init.lua
index aaac13b..34e4441 100644
--- a/game/love_src/src/world/top_down_race/init.lua
+++ b/game/love_src/src/world/top_down_race/init.lua
@@ -31,13 +31,13 @@ function wrapper:load(_args)
     {
       assemblage = racer.assemble,
       data = {
-        accel = 10.0,
+        accel = 20.0,
         brake = 10.0,
-        grip = 10.0,
+        grip = 2.0,
         max_speed = 100.0,
-        steer = 10.0,
+        steer = 2.0,
         velocity = 10.0,
-        decel = 2.0,
+        decel = 10.0,
         drag = 2.0
       }
     }
diff --git a/game/love_src/src/world/top_down_race/system/velocity.lua b/game/love_src/src/world/top_down_race/system/velocity.lua
index 5b7c076..0da69fa 100644
--- a/game/love_src/src/world/top_down_race/system/velocity.lua
+++ b/game/love_src/src/world/top_down_race/system/velocity.lua
@@ -92,6 +92,30 @@ function system:load()
   end
 end
 
+local function get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed)
+  local new_accel
+  local new_min_speed = 0
+  if (up) then
+    new_accel = racing_phy.gas(accel, drag)
+  elseif(down) then
+    new_accel = racing_phy.brake(decel, drag, grip)
+    new_min_speed = -max_speed
+  else
+    new_accel = racing_phy.roam(decel, drag)
+  end
+  return racing_phy.accelerate(dt, 1, velocity, max_speed, new_accel, new_min_speed)
+end
+
+local function get_angle(dt, left, right, steer, grip, drag, velocity, max_speed)
+  local new_angle = 0
+  if (left) then
+    new_angle = - 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed) * dt
+  elseif (right) then
+    new_angle = 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed) * dt
+  end
+  return new_angle
+end
+
 function system:update(dt)
   for _, e in ipairs(self.pool) do
     local accel, brake, grip, max_speed, steer, velocity, drag, decel = get(e)
@@ -101,31 +125,21 @@ function system:update(dt)
     local left = love.keyboard.isDown("left")
     local right = love.keyboard.isDown("right")
 
-    if (up) then
-      e[race.dict.velocity].data = racing_phy.accelerate(dt, 1, velocity, max_speed, accel - drag)
-    elseif(down) then
-      e[race.dict.velocity].data = racing_phy.accelerate(dt, -1, velocity, max_speed, accel - drag, -max_speed)
-    else
-      e[race.dict.velocity].data = racing_phy.accelerate(dt, 1, velocity, max_speed, -drag -decel)
-    end
+    e[race.dict.velocity].data = get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed)
 
+    local pos_x, pos_y = e["race.pos"].data[1], e["race.pos"].data[2]
     local angle = e["race.angle"].data
-    if (left) then
-      e["race.angle"].data = angle - 1 * dt
-    end
-    if (right) then
-      e["race.angle"].data = angle + 1 * dt
-    end
-
-    angle = e["race.angle"].data
-    cos = math.cos(angle)
-    sin = math.sin(angle)
+    local new_angle = get_angle(dt, left, right, steer, grip, drag,velocity, max_speed)
+    e["race.angle"].data = angle + new_angle
 
     velocity = e[race.dict.velocity].data
+    angle = e["race.angle"].data
 
-    e["race.pos"].data[1] = e["race.pos"].data[1] + velocity * cos
-    e["race.pos"].data[2] = e["race.pos"].data[2] + velocity * sin
-    -- print(racing_phy.drift(dt, 1, velocity, max_speed, 2, 10))
+    local centrifugal = racing_phy.centrifugal_force(dt, velocity, max_speed)
+    local goal_x, goal_y = racing_phy.drift(dt, pos_x, pos_y, velocity, max_speed, angle, centrifugal)
+
+    e["race.pos"].data[1] = goal_x
+    e["race.pos"].data[2] = goal_y
   end
 end