base/Object.lua

   1 --the Object class
   2 --all objects should descend from this
   3
   4 Object = {}
   5 Object.x = 0
   6 Object.y = 0
   7 Object.w = 0
   8 Object.h = 0
   9
  10 --movement
  11 Object.angle = 0  --angle in degrees
  12 Object.speed = 0  --speed in pixels
  13
  14 --rotation
  15 Object.rotation = 0
  16 Object.angular_velocity = 0
  17
  18 --global physics stuff
  19 Object.falling_speed = 0  -- the current "falling" speed of an Object
  20 Object.gravity = false  --whether an Object is affected by gravity
  21 Object.wind = false    --whether an Object is affected by wind
  22 Object.weight = nil --weight of the object - used for wind calculation
  23
  24 Object.image = nil --this should hold the image of the enemy
  25 Object.rects = nil --this field should hold the collision Rect objects
  26
  27 Object.type = "Object" --for each class, this should be set to a unique identifier. it is used in collision detection
  28
  29 Object.max_updates = -1 --if set to a non-negative, non-zero number, object will automatically collect itself after this many updates
  30 Object.num_updates = 0 --current count of updates
  31
  32 Object.death_anim = false --setting this to true will prevent it from colliding
  33 Object.collect = false  --set to true to cause resource manager to collect this object
  34
  35 function Object:new(o)
  36   o = o or {}
  37   setmetatable(o, self)
  38   self.__index = self
  39   self.rect = ObjectList:new()
  40   return o
  41 end
  42
  43 --updates the object's state
  44 function Object:update(delta)
  45   if delta ~= nil then
  46     delta = delta/1000
  47   end
  48
  49   self.x = self.x + math.cos(math.rad(self.angle)) * (self.speed * (delta or 1))
  50   self.y = self.y + math.sin(math.rad(-1 * self.angle)) * (self.speed * (delta or 1))
  51   self.rotation = (self.rotation + (self.angular_velocity * (delta or 1))) % 360
  52
  53   --gravity calculations
  54   if(self.gravity == true and gravity_strength ~= 0 and gravity_strength ~= nil and gravity_angle ~= nil) then
  55     self.x = self.x + math.cos(math.rad(gravity_angle)) * self.falling_speed * (delta or 1)
  56     self.y = self.y + math.sin(math.rad(-1 * gravity_angle)) * self.falling_speed * (delta or 1)
  57
  58   --updating after calculations allows for collision to work properly
  59     self.falling_speed = self.falling_speed + gravity_strength
  60   end
  61
  62
  63   if(self.wind == true and wind_strength ~= 0 and wind_strength ~= nil and wind_angle ~= nil and self.weight ~= nil) then
  64     self.x = self.x + ((math.cos(math.rad(wind_angle)) * wind_strength) / self.weight) * (delta or 1)
  65     self.y = self.y + ((math.sin(math.rad(-1 * wind_angle)) * wind_strength) / self.weight) * (delta or 1)
  66   end
  67
  68   --Object self-collect check (mostly for particle systems)
  69   if self.max_updates > 0 then
  70     self.num_updates = self.num_updates + 1
  71     if self.num_updates >= self.max_updates then
  72       self.collect = true
  73     end
  74   end
  75
  76 end
  77
  78 --default draw routine
  79 function Object:draw()
  80   --last option is to re-center after rotating
  81   blit(self.image, self.x, self.y, self.rotation, true)
  82 end
  83
  84 --there is no predefined collision behavior
  85 -- "ids" is the list of Rect ids that have been collided with
  86 -- "type" is the type of the Object that is colliding
  87 function Object:collide(type, ids)
  88
  89 end
  90
  91 --returns the coordinate of the center
  92 function Object:get_center()
  93   return (self.x + self.w)/2, (self.y + self.h)/2
  94 end