add inertia and fix physics

game/love_src/src/system/racing_phy.lua

@@ -13,51 +13,46 @@ local function accelerate(dt, gas_input, speed, max_speed, accel, min_speed)
   return new_speed
 end
 
-local function centrifugal_force(dt, speed, max_speed)
+local function centrifugal_force(dt, mass, 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 mass * dy * speed * speed
-  return 1 * dy * speed * speed
 end
 
-local function drift(dt, pos_x, pos_y, speed, max_speed, angle, centrifugal)
+local function drift(dt, pos_x, pos_y, speed, max_speed, angle, scale_x, scale_y)
   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
+  local dx = dt * 2.0 * speed_percent -- at top speed, should be able to cross from left to right (-1 to 1) in 1 second
-  local dy = dt * 2 * speed_percent
+  local dy = dt * 2.0 * speed_percent
   cos = math.cos(angle)
   sin = math.sin(angle)
 
-  return pos_x + (dx * speed_percent * cos * centrifugal),
+  return pos_x + (dx * speed_percent * cos) * (scale_x or 1),
-    pos_y + (dy * speed_percent * sin * centrifugal)
+    pos_y + (dy * speed_percent * sin) * (scale_y or 1)
 end
 
-local function gas(accel, drag, friction)
+-- local function gas(accel, drag, friction)
-  friction = friction or 0
+--   friction = friction or 0
-  return accel - drag - friction
+--   return accel - drag - friction
-end
+-- end
 
-local function brake(decel, drag, grip, friction)
+-- local function brake(decel, drag, grip, friction)
-  friction = friction or 0
+--   friction = friction or 0
-  return - decel - drag - grip - friction
+--   return - decel - drag - grip - friction
-end
+-- end
 
-local function roam(decel, drag, friction)
+-- local function roam(decel, drag, friction)
-  friction = friction or 0
+--   friction = friction or 0
-  return - decel - drag - friction
+--   return - decel - drag - friction
-end
+-- end
 
-local function steer(_steer, grip, drag, velocity, friction)
+-- local function steer(_steer, grip, drag, velocity, friction)
-  friction = friction or 0
+--   friction = friction or 0
-  return _steer + grip + drag - velocity + friction
+--   return _steer + grip + drag - velocity + friction
-end
+-- end
 
 return {
   accelerate = accelerate,
   drift = drift,
-  gas = gas,
-  brake = brake,
-  steer = steer,
-  roam = roam,
   centrifugal_force = centrifugal_force
 }

game/love_src/src/world/top_down_race/component/race.lua

@@ -9,7 +9,8 @@ components.dict = {
   brake = "race.brake",
   decel = "race.decel",
   drag = "race.drag",
-  direction = "race.direction"
+  mass = "race.mass",
+  inertia = "race.inertia"
 }
 
 function components.velocity (c, x)
@@ -44,8 +45,12 @@ function components.drag (c, x)
   c.data = x
 end
 
-function components.direction (c, x)
+function components.mass (c, x)
   c.data = x
 end
 
+function components.inertia (c, x, y)
+  c.data = {x, y}
+end
+
 return components

game/love_src/src/world/top_down_race/init.lua

@@ -32,13 +32,14 @@ function wrapper:load(_args)
       assemblage = racer.assemble,
       data = {
         accel = 20.0,
-        brake = 10.0,
+        brake = 1.0,
-        grip = 2.0,
+        grip = 1.0,
-        max_speed = 100.0,
+        max_speed = 50.0,
-        steer = 2.0,
+        steer = 1.0,
-        velocity = 10.0,
+        velocity = 0.0,
-        decel = 10.0,
+        inertia = {0.0, 0.0},
-        drag = 2.0
+        drag = 1.0,
+        mass = 1.0
       }
     }
   })

game/love_src/src/world/top_down_race/system/velocity.lua

@@ -18,8 +18,9 @@ system.pool = {
     race.dict.max_speed,
     race.dict.steer,
     race.dict.velocity,
-    race.dict.decel,
+    race.dict.inertia,
-    race.dict.drag
+    race.dict.drag,
+    race.dict.mass
   }
 }
 
@@ -30,8 +31,9 @@ system.components = {
   [race.dict.max_speed] = race.max_speed,
   [race.dict.steer] = race.steer,
   [race.dict.velocity] = race.velocity,
-  [race.dict.decel] = race.decel,
+  [race.dict.inertia] = race.inertia,
-  [race.dict.drag] = race.drag
+  [race.dict.drag] = race.drag,
+  [race.dict.mass] = race.mass
 }
 
 function system.new()
@@ -55,7 +57,8 @@ local function get(e)
     e[race.dict.steer].data,
     e[race.dict.velocity].data,
     e[race.dict.drag].data,
-    e[race.dict.decel].data
+    e[race.dict.inertia].data,
+    e[race.dict.mass].data
 end
 
 local function draw(text, x, y, sx, sy, angle, image, origin)
@@ -101,7 +104,7 @@ local frictions = {
       0, 0, lw/2, lh
     },
     color = {0, 255/255, 0},
-    friction = 5
+    friction = 2
   },
   {
     name = "pavement",
@@ -110,32 +113,70 @@ local frictions = {
       lw/2, 0, lw/2, lh
     },
     color = {0, 255/255, 255/255},
-    friction = 0
+    friction = 1
   }
 }
 
-local function get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed, friction)
+local function accel_force(up, down, accel, brake, inertia)
-  local new_accel
+  local force
-  local new_min_speed = 0
   if (up) then
-    new_accel = racing_phy.gas(accel, drag, friction)
+    force = accel - inertia
   elseif(down) then
-    new_accel = racing_phy.brake(decel, drag, grip, friction)
+    force = - brake + inertia
-    new_min_speed = -max_speed
   else
-    new_accel = racing_phy.roam(decel, drag, friction)
+    force = inertia
   end
-  return racing_phy.accelerate(dt, 1, velocity, max_speed, new_accel, new_min_speed)
+  return force
 end
 
-local function get_angle(dt, left, right, steer, grip, drag, velocity, max_speed, friction)
+local function steer_force(left, right, steer, inertia)
-  local new_angle = 0
   if (left) then
-    new_angle = - 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed, friction) * dt
+    force = -steer + inertia
   elseif(right) then
-    new_angle = 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed, friction) * dt
+    force = steer - inertia
+  else
+    force = inertia
   end
-  return new_angle
+  return force
+end
+
+local function grip_force(grip, friction)
+  return friction * grip
+end
+
+local function add_friction(force, grip, friction, tire_c, floor_c)
+  local f_grip = grip_force(grip, friction)
+  if (force > 0) then
+    -- tire - floor
+    force = force + tire_c * f_grip - floor_c * f_grip
+  elseif (force < 0) then
+    force = force - tire_c * f_grip + floor_c * f_grip
+  else
+    force = force
+  end
+  return force
+end
+
+local function add_drag(force, drag)
+  if (force > 0) then
+    force = force - drag
+  elseif (force < 0) then
+    force = force + drag
+  else
+    force = force
+  end
+  return force
+end
+
+local function add_centrifugal(force, centrifugal)
+  if (force > 0) then
+    force = force - centrifugal
+  elseif (force < 0) then
+    force = force + centrifugal
+  else
+    force = force
+  end
+  return force
 end
 
 -- x1 y1        -- (x1 + w1) y1
@@ -162,7 +203,7 @@ end
 
 function system:update(dt)
   for _, e in ipairs(self.pool) do
-    local accel, brake, grip, max_speed, steer, velocity, drag, decel = get(e)
+    local accel, brake, grip, max_speed, steer, velocity, drag, inertia, mass = get(e)
 
     local up = love.keyboard.isDown("up")
     local down = love.keyboard.isDown("down")
@@ -173,17 +214,31 @@ function system:update(dt)
 
     local friction = get_friction(pos_x, pos_y, frictions)
 
-    e[race.dict.velocity].data = get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed, friction)
+    local f_forward = accel_force(up, down, accel, brake, inertia[1])
+    local f_lateral = steer_force(left, right, steer, inertia[2])
 
-    local angle = e["race.angle"].data
+    f_forward = add_friction(f_forward, grip, friction, 1.0, 0.5)
-    local new_angle = get_angle(dt, left, right, steer, grip, drag,velocity, max_speed, friction)
+    f_lateral = add_friction(f_lateral, grip, friction, 1.0, 0.5)
-    e["race.angle"].data = angle + new_angle
 
-    velocity = e[race.dict.velocity].data
+    f_forward = add_drag(f_forward, drag)
-    angle = e["race.angle"].data
+    f_lateral = add_drag(f_lateral, drag)
 
-    local centrifugal = racing_phy.centrifugal_force(dt, velocity, max_speed)
+    if (mass == 0) then
-    local goal_x, goal_y = racing_phy.drift(dt, pos_x, pos_y, velocity, max_speed, angle, centrifugal)
+      mass = 1
+    end
+
+    local new_velocity = racing_phy.accelerate(dt, 1, velocity, max_speed, f_forward*dt/mass, 0)
+    local centrifugal = racing_phy.centrifugal_force(dt, mass, new_velocity, max_speed)
+    f_lateral = add_centrifugal(f_lateral, centrifugal)
+
+    e[race.dict.inertia].data = {f_forward * dt, f_lateral * dt}
+
+    local new_angle =  e["race.angle"].data + f_lateral * dt/mass
+    e["race.angle"].data = new_angle
+    e[race.dict.velocity].data = new_velocity
+
+    local goal_x, goal_y = racing_phy.drift(dt, pos_x, pos_y, new_velocity, max_speed, new_angle, 100000, 100000)
+    -- print("force_forward", f_forward, "f_lateral", f_lateral, "velocity", new_velocity, "angle", new_angle, "goal_x", goal_x, "goal_y", goal_y)
 
     e["race.pos"].data[1] = goal_x
     e["race.pos"].data[2] = goal_y

game/love_src/src/world/top_down_race/template/racer.lua

@@ -8,9 +8,10 @@ template.default_data = {
   grip = 10.0,
   max_speed = 10.0,
   steer = 10.0,
-  velocity = 10.0,
+  velocity = 0.0,
-  decel = 5.0,
+  inertia = {0.0, 0.0},
-  drag = 2.0
+  drag = 2.0,
+  mass = 10.0
 }
 function template.assemble(e, data)
   e:give(race.dict.accel, data.accel)
@@ -19,8 +20,9 @@ function template.assemble(e, data)
   e:give(race.dict.max_speed, data.max_speed)
   e:give(race.dict.steer, data.steer)
   e:give(race.dict.velocity, data.velocity)
-  e:give(race.dict.decel, data.decel)
+  e:give(race.dict.inertia, data.inertia[1], data.inertia[2])
   e:give(race.dict.drag, data.drag)
+  e:give(race.dict.mass, data.mass)
 end
 
 return template