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 Object.x_offset = 0
  11 Object.y_offset = 0
  12
  13 --movement
  14 Object.angle = 0  --angle in degrees
  15 Object.speed = 0  --speed in pixels
  16
  17 --rotation
  18 Object.rotation = 0
  19 Object.angular_velocity = 0
  20
  21 --global physics stuff
  22 Object.falling_speed = 0  -- the current "falling" speed of an Object
  23 Object.gravity = false  --whether an Object is affected by gravity
  24 Object.wind = false    --whether an Object is affected by wind
  25 Object.weight = nil --weight of the object - used for wind calculation
  26
  27 Object.image = nil --this should hold the image of the Object
  28 Object.rects = ObjectList:new() --this field should hold the collision Rect objects
  29
  30 Object.type = "Object" --for each class, this should be set to a unique identifier. it is used in collision detection
  31
  32 Object.max_updates = -1 --if set to a non-negative, non-zero number, object will automatically collect itself after this many updates
  33 Object.num_updates = 0 --current count of updates
  34
  35 Object.death_anim = false --setting this to true will prevent it from colliding
  36 Object.collect = false  --set to true to cause resource manager to collect this object
  37
  38 function Object:new(o)
  39   o = o or {}
  40   setmetatable(o, self)
  41   self.__index = self
  42   self.rect = ObjectList:new()
  43   return o
  44 end
  45
  46 --updates the object's state
  47 function Object:update(delta)
  48   if delta ~= nil then
  49     delta = delta/1000
  50   end
  51
  52   self.x = self.x + math.cos(math.rad(self.angle)) * (self.speed * (delta or 1))
  53   self.y = self.y + math.sin(math.rad(-1 * self.angle)) * (self.speed * (delta or 1))
  54   self.rotation = (self.rotation + (self.angular_velocity * (delta or 1))) % 360
  55
  56   --gravity calculations
  57   if(self.gravity == true and gravity_strength ~= 0 and gravity_strength ~= nil and gravity_angle ~= nil) then
  58     self.x = self.x + math.cos(math.rad(gravity_angle)) * self.falling_speed * (delta or 1)
  59     self.y = self.y + math.sin(math.rad(-1 * gravity_angle)) * self.falling_speed * (delta or 1)
  60
  61   --updating after calculations allows for collision to work properly
  62     self.falling_speed = self.falling_speed + gravity_strength
  63   end
  64
  65
  66   if(self.wind == true and wind_strength ~= 0 and wind_strength ~= nil and wind_angle ~= nil and self.weight ~= nil) then
  67     self.x = self.x + ((math.cos(math.rad(wind_angle)) * wind_strength) / self.weight) * (delta or 1)
  68     self.y = self.y + ((math.sin(math.rad(-1 * wind_angle)) * wind_strength) / self.weight) * (delta or 1)
  69   end
  70
  71   --Object self-collect check (mostly for particle systems)
  72   if self.max_updates > 0 then
  73     self.num_updates = self.num_updates + 1
  74     if self.num_updates >= self.max_updates then
  75       self.collect = true
  76     end
  77   end
  78
  79 end
  80
  81 --default draw routine
  82 function Object:draw()
  83   --last option is to re-center after rotating
  84   blit(self.image, self.x-self.x_offset, self.y-self.y_offset, self.rotation, true)
  85 end
  86
  87 --there is no predefined collision behavior
  88 -- "ids" is the list of Rect ids that have been collided with
  89 -- "type" is the type of the Object that is colliding
  90 function Object:collide(ids, type)
  91
  92 end
  93
  94 --returns the coordinate of the center
  95 function Object:get_center()
  96   return math.floor(self.x + (self.w/2)), math.floor(self.y + (self.h/2))
  97 end
  98
  99 --sets the drawing offset of the sprite
 100 function Object:set_origin(x,y)
 101   self.x_offset = x
 102   self.y_offset = y
 103 end