add friction

game/love_src/src/system/racing_phy.lua

@@ -32,20 +32,24 @@ local function drift(dt, pos_x, pos_y, speed, max_speed, angle, centrifugal)
     pos_y + (dy * speed_percent * sin * centrifugal)
 end
 
-local function gas(accel, drag)
+local function gas(accel, drag, friction)
-  return accel - drag
+  friction = friction or 0
+  return accel - drag - friction
 end
 
-local function brake(decel, drag, grip)
+local function brake(decel, drag, grip, friction)
-  return - decel - drag - grip
+  friction = friction or 0
+  return - decel - drag - grip - friction
 end
 
-local function roam(decel, drag)
+local function roam(decel, drag, friction)
-  return - decel - drag
+  friction = friction or 0
+  return - decel - drag - friction
 end
 
-local function steer(_steer, grip, drag, velocity)
+local function steer(_steer, grip, drag, velocity, friction)
-  return _steer + grip + drag - velocity
+  friction = friction or 0
+  return _steer + grip + drag - velocity + friction
 end
 
 return {

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

@@ -92,30 +92,74 @@ function system:load()
   end
 end
 
-local function get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed)
+local lw, lh = love.graphics.getDimensions()
+local frictions = {
+  {
+    name = "grass",
+    colliders = {
+      -- x, y, w, h
+      0, 0, lw/2, lh
+    },
+    color = {0, 255/255, 0},
+    friction = 5
+  },
+  {
+    name = "pavement",
+    colliders = {
+      -- x, y, w, h
+      lw/2, 0, lw/2, lh
+    },
+    color = {0, 255/255, 255/255},
+    friction = 0
+  }
+}
+
+local function get_velocity(dt, up, down, accel, drag, decel, grip, velocity, max_speed, friction)
   local new_accel
   local new_min_speed = 0
   if (up) then
-    new_accel = racing_phy.gas(accel, drag)
+    new_accel = racing_phy.gas(accel, drag, friction)
   elseif(down) then
-    new_accel = racing_phy.brake(decel, drag, grip)
+    new_accel = racing_phy.brake(decel, drag, grip, friction)
     new_min_speed = -max_speed
   else
-    new_accel = racing_phy.roam(decel, drag)
+    new_accel = racing_phy.roam(decel, drag, friction)
   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 function get_angle(dt, left, right, steer, grip, drag, velocity, max_speed, friction)
   local new_angle = 0
   if (left) then
-    new_angle = - 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed) * dt
+    new_angle = - 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed, friction) * dt
   elseif (right) then
-    new_angle = 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed) * dt
+    new_angle = 1 * racing_phy.steer(steer, grip, drag, velocity / max_speed, friction) * dt
   end
   return new_angle
 end
 
+-- x1 y1        -- (x1 + w1) y1
+--          x2 y2
+-- x1 (y1 + h1) -- (x1 + w1) (y1 + h1)
+local function is_inside(x1,y1,w1,h1, x2,y2)
+  return x1 < x2 and
+         x2 < x1+w1 and
+         y1 < y2 and
+         y2 < y1+h1
+end
+
+local function get_friction(pos_x, pos_y, floors)
+  local friction = 0
+  for _,f in ipairs(floors) do
+    local fx, fy, fw, fh = f.colliders[1], f.colliders[2], f.colliders[3], f.colliders[4]
+    if (is_inside(fx, fy, fw, fh, pos_x, pos_y)) then
+      friction = f.friction
+      break
+    end
+  end
+  return friction
+end
+
 function system:update(dt)
   for _, e in ipairs(self.pool) do
     local accel, brake, grip, max_speed, steer, velocity, drag, decel = get(e)
@@ -125,11 +169,14 @@ function system:update(dt)
     local left = love.keyboard.isDown("left")
     local right = love.keyboard.isDown("right")
 
-    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 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 angle = e["race.angle"].data
-    local new_angle = get_angle(dt, left, right, steer, grip, drag,velocity, max_speed)
+    local new_angle = get_angle(dt, left, right, steer, grip, drag,velocity, max_speed, friction)
     e["race.angle"].data = angle + new_angle
 
     velocity = e[race.dict.velocity].data
@@ -144,6 +191,13 @@ function system:update(dt)
 end
 
 function system:draw()
+  for _, f in ipairs(frictions) do
+    love.graphics.push()
+    love.graphics.setColor(f.color)
+    love.graphics.rectangle("fill", f.colliders[1], f.colliders[2], f.colliders[3], f.colliders[4])
+    love.graphics.setColor(1, 1, 1)
+    love.graphics.pop()
+  end
   for _, e in ipairs(self.pool) do
     local accel, brake, grip, max_speed, steer, velocity = get(e)
     local x, y, sx, sy, angle = e["race.pos"].data[1], e["race.pos"].data[2], e["race.scale"].data[1], e["race.scale"].data[2], e["race.angle"].data